diff --git a/harness/resizableArrayBufferUtils.js b/harness/resizableArrayBufferUtils.js
index db58f521f8..9dad8ccb83 100644
--- a/harness/resizableArrayBufferUtils.js
+++ b/harness/resizableArrayBufferUtils.js
@@ -9,7 +9,7 @@ defines:
   - ctors
   - MyBigInt64Array
   - CreateResizableArrayBuffer
-  - WriteToTypedArray
+  - MayNeedBigInt
   - Convert
   - ToNumbers
   - CreateRabForTest
@@ -74,14 +74,6 @@ function CreateResizableArrayBuffer(byteLength, maxByteLength) {
   return new ArrayBuffer(byteLength, { maxByteLength: maxByteLength });
 }
 
-function WriteToTypedArray(array, index, value) {
-  if (array instanceof BigInt64Array || array instanceof BigUint64Array) {
-    array[index] = BigInt(value);
-  } else {
-    array[index] = value;
-  }
-}
-
 function Convert(item) {
   if (typeof item == 'bigint') {
     return Number(item);
@@ -98,12 +90,21 @@ function ToNumbers(array) {
   return result;
 }
 
+function MayNeedBigInt(ta, n) {
+  assert.sameValue(typeof n, 'number');
+  if ((BigInt64Array !== 'undefined' && ta instanceof BigInt64Array)
+      || (BigUint64Array !== 'undefined' && ta instanceof BigUint64Array)) {
+    return BigInt(n);
+  }
+  return n;
+}
+
 function CreateRabForTest(ctor) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
   return rab;
 }
diff --git a/test/built-ins/Array/prototype/at/typed-array-resizable-buffer.js b/test/built-ins/Array/prototype/at/typed-array-resizable-buffer.js
index 238ebab160..a4f8afbdcc 100644
--- a/test/built-ins/Array/prototype/at/typed-array-resizable-buffer.js
+++ b/test/built-ins/Array/prototype/at/typed-array-resizable-buffer.js
@@ -24,7 +24,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   let ta_write = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(ta_write, i, i);
+    ta_write[i] = MayNeedBigInt(ta_write, i);
   }
   assert.sameValue(ArrayAtHelper(fixedLength, -1), 3);
   assert.sameValue(ArrayAtHelper(lengthTracking, -1), 3);
diff --git a/test/built-ins/Array/prototype/copyWithin/resizable-buffer.js b/test/built-ins/Array/prototype/copyWithin/resizable-buffer.js
index 02918d2980..7c0cda3a29 100644
--- a/test/built-ins/Array/prototype/copyWithin/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/copyWithin/resizable-buffer.js
@@ -24,7 +24,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   // Orig. array: [0, 1, 2, 3]
@@ -41,7 +41,7 @@ for (let ctor of ctors) {
     3
   ]);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
   ArrayCopyWithinHelper(fixedLengthWithOffset, 0, 1);
   assert.compareArray(ToNumbers(fixedLengthWithOffset), [
@@ -49,7 +49,7 @@ for (let ctor of ctors) {
     3
   ]);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
   ArrayCopyWithinHelper(lengthTracking, 0, 2);
   assert.compareArray(ToNumbers(lengthTracking), [
@@ -67,7 +67,7 @@ for (let ctor of ctors) {
   // Shrink so that fixed length TAs go out of bounds.
   rab.resize(3 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 3; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   // Orig. array: [0, 1, 2]
@@ -99,7 +99,7 @@ for (let ctor of ctors) {
 
   // Shrink so that the TAs with offset go out of bounds.
   rab.resize(1 * ctor.BYTES_PER_ELEMENT);
-  WriteToTypedArray(taWrite, 0, 0);
+  taWrite[0] = MayNeedBigInt(taWrite, 0);
   ArrayCopyWithinHelper(fixedLength, 0, 1, 1);
   ArrayCopyWithinHelper(fixedLengthWithOffset, 0, 1, 1);
   ArrayCopyWithinHelper(lengthTrackingWithOffset, 0, 1, 1);
@@ -121,7 +121,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   // Orig. array: [0, 1, 2, 3, 4, 5]
@@ -138,7 +138,7 @@ for (let ctor of ctors) {
     3
   ]);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
   ArrayCopyWithinHelper(fixedLengthWithOffset, 0, 1);
   assert.compareArray(ToNumbers(fixedLengthWithOffset), [
@@ -146,7 +146,7 @@ for (let ctor of ctors) {
     3
   ]);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   //              [0, 1, 2, 3, 4, 5, ...] << lengthTracking
@@ -161,7 +161,7 @@ for (let ctor of ctors) {
     5
   ]);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   //                    [2, 3, 4, 5, ...] << lengthTrackingWithOffset
diff --git a/test/built-ins/Array/prototype/entries/resizable-buffer.js b/test/built-ins/Array/prototype/entries/resizable-buffer.js
index 7f20fa608c..9563fb0fdf 100644
--- a/test/built-ins/Array/prototype/entries/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/entries/resizable-buffer.js
@@ -35,7 +35,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -128,7 +128,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/Array/prototype/every/resizable-buffer.js b/test/built-ins/Array/prototype/every/resizable-buffer.js
index b6f68e0f69..c2f0fe680b 100644
--- a/test/built-ins/Array/prototype/every/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/every/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -86,7 +86,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/Array/prototype/filter/resizable-buffer.js b/test/built-ins/Array/prototype/filter/resizable-buffer.js
index df38c65791..6e5a291971 100644
--- a/test/built-ins/Array/prototype/filter/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/filter/resizable-buffer.js
@@ -19,7 +19,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   // Orig. array: [0, 1, 2, 3]
@@ -77,7 +77,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   // Orig. array: [0, 1, 2, 3, 4, 5]
diff --git a/test/built-ins/Array/prototype/find/resizable-buffer.js b/test/built-ins/Array/prototype/find/resizable-buffer.js
index bcf793ebe5..45217f3db0 100644
--- a/test/built-ins/Array/prototype/find/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/find/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -69,10 +69,10 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 0);
+    taWrite[i] = MayNeedBigInt(taWrite, 0);
   }
-  WriteToTypedArray(taWrite, 4, 2);
-  WriteToTypedArray(taWrite, 5, 4);
+  taWrite[4] = MayNeedBigInt(taWrite, 2);
+  taWrite[5] = MayNeedBigInt(taWrite, 4);
 
   // Orig. array: [0, 0, 0, 0, 2, 4]
   //              [0, 0, 0, 0] << fixedLength
diff --git a/test/built-ins/Array/prototype/findIndex/resizable-buffer.js b/test/built-ins/Array/prototype/findIndex/resizable-buffer.js
index 09e4191583..4826e06c96 100644
--- a/test/built-ins/Array/prototype/findIndex/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/findIndex/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -69,10 +69,10 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 0);
+    taWrite[i] = MayNeedBigInt(taWrite, 0);
   }
-  WriteToTypedArray(taWrite, 4, 2);
-  WriteToTypedArray(taWrite, 5, 4);
+  taWrite[4] = MayNeedBigInt(taWrite, 2);
+  taWrite[5] = MayNeedBigInt(taWrite, 4);
 
   // Orig. array: [0, 0, 0, 0, 2, 4]
   //              [0, 0, 0, 0] << fixedLength
diff --git a/test/built-ins/Array/prototype/findLast/resizable-buffer.js b/test/built-ins/Array/prototype/findLast/resizable-buffer.js
index 2c716576e7..8eeb665a27 100644
--- a/test/built-ins/Array/prototype/findLast/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/findLast/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -69,10 +69,10 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 0);
+    taWrite[i] = MayNeedBigInt(taWrite, 0);
   }
-  WriteToTypedArray(taWrite, 4, 2);
-  WriteToTypedArray(taWrite, 5, 4);
+  taWrite[4] = MayNeedBigInt(taWrite, 2);
+  taWrite[5] = MayNeedBigInt(taWrite, 4);
 
   // Orig. array: [0, 0, 0, 0, 2, 4]
   //              [0, 0, 0, 0] << fixedLength
diff --git a/test/built-ins/Array/prototype/findLastIndex/resizable-buffer.js b/test/built-ins/Array/prototype/findLastIndex/resizable-buffer.js
index f55f0f3f80..9b94240fb6 100644
--- a/test/built-ins/Array/prototype/findLastIndex/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/findLastIndex/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -69,10 +69,10 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 0);
+    taWrite[i] = MayNeedBigInt(taWrite, 0);
   }
-  WriteToTypedArray(taWrite, 4, 2);
-  WriteToTypedArray(taWrite, 5, 4);
+  taWrite[4] = MayNeedBigInt(taWrite, 2);
+  taWrite[5] = MayNeedBigInt(taWrite, 4);
 
   // Orig. array: [0, 0, 0, 0, 2, 4]
   //              [0, 0, 0, 0] << fixedLength
diff --git a/test/built-ins/Array/prototype/forEach/resizable-buffer.js b/test/built-ins/Array/prototype/forEach/resizable-buffer.js
index 3b3936f90e..57523ddc27 100644
--- a/test/built-ins/Array/prototype/forEach/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/forEach/resizable-buffer.js
@@ -19,7 +19,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -91,7 +91,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/Array/prototype/includes/coerced-searchelement-fromindex-resize.js b/test/built-ins/Array/prototype/includes/coerced-searchelement-fromindex-resize.js
index 96c5ca2ff4..965a23ddf6 100644
--- a/test/built-ins/Array/prototype/includes/coerced-searchelement-fromindex-resize.js
+++ b/test/built-ins/Array/prototype/includes/coerced-searchelement-fromindex-resize.js
@@ -10,13 +10,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer, Array.prototype.includes]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const fixedLength = new ctor(rab, 0, 4);
@@ -61,7 +54,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, 1);
   }
   let evil = {
     valueOf: () => {
@@ -77,7 +70,7 @@ for (let ctor of ctors) {
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
-  WriteToTypedArray(lengthTracking, 0, 1);
+  lengthTracking[0] = MayNeedBigInt(lengthTracking, 1);
   let evil = {
     valueOf: () => {
       rab.resize(6 * ctor.BYTES_PER_ELEMENT);
diff --git a/test/built-ins/Array/prototype/includes/resizable-buffer.js b/test/built-ins/Array/prototype/includes/resizable-buffer.js
index b9a78cef9a..c31d5827d2 100644
--- a/test/built-ins/Array/prototype/includes/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/includes/resizable-buffer.js
@@ -9,13 +9,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer, Array.prototype.includes]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const fixedLength = new ctor(rab, 0, 4);
@@ -26,7 +19,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -100,7 +93,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/Array/prototype/indexOf/coerced-searchelement-fromindex-grow.js b/test/built-ins/Array/prototype/indexOf/coerced-searchelement-fromindex-grow.js
index fc1c3e0f7d..cc0b2b7dcc 100644
--- a/test/built-ins/Array/prototype/indexOf/coerced-searchelement-fromindex-grow.js
+++ b/test/built-ins/Array/prototype/indexOf/coerced-searchelement-fromindex-grow.js
@@ -10,19 +10,12 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 // Growing + length-tracking TA.
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, 1);
   }
   let evil = {
     valueOf: () => {
@@ -40,7 +33,7 @@ for (let ctor of ctors) {
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
-  WriteToTypedArray(lengthTracking, 0, 1);
+  lengthTracking[0] = MayNeedBigInt(lengthTracking, 1);
   let evil = {
     valueOf: () => {
       rab.resize(6 * ctor.BYTES_PER_ELEMENT);
diff --git a/test/built-ins/Array/prototype/indexOf/coerced-searchelement-fromindex-shrink.js b/test/built-ins/Array/prototype/indexOf/coerced-searchelement-fromindex-shrink.js
index 9e803e491a..ab4c4ae4d5 100644
--- a/test/built-ins/Array/prototype/indexOf/coerced-searchelement-fromindex-shrink.js
+++ b/test/built-ins/Array/prototype/indexOf/coerced-searchelement-fromindex-shrink.js
@@ -10,13 +10,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 // Shrinking + fixed-length TA.
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
@@ -52,7 +45,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i);
   }
   let evil = {
     valueOf: () => {
diff --git a/test/built-ins/Array/prototype/indexOf/resizable-buffer.js b/test/built-ins/Array/prototype/indexOf/resizable-buffer.js
index 74f232dd2c..cb66e19be6 100644
--- a/test/built-ins/Array/prototype/indexOf/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/indexOf/resizable-buffer.js
@@ -9,13 +9,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const fixedLength = new ctor(rab, 0, 4);
@@ -26,7 +19,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, Math.floor(i / 2));
+    taWrite[i] = MayNeedBigInt(taWrite, Math.floor(i / 2));
   }
 
   // Orig. array: [0, 0, 1, 1]
@@ -98,7 +91,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, Math.floor(i / 2));
+    taWrite[i] = MayNeedBigInt(taWrite, Math.floor(i / 2));
   }
 
   // Orig. array: [0, 0, 1, 1, 2, 2]
diff --git a/test/built-ins/Array/prototype/join/resizable-buffer.js b/test/built-ins/Array/prototype/join/resizable-buffer.js
index e28414ab00..9eb672bb84 100644
--- a/test/built-ins/Array/prototype/join/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/join/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
 
   // Write some data into the array.
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -66,7 +66,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/Array/prototype/keys/resizable-buffer.js b/test/built-ins/Array/prototype/keys/resizable-buffer.js
index 295ce3612b..de1d7436e2 100644
--- a/test/built-ins/Array/prototype/keys/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/keys/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   assert.compareArray(Array.from(Array.prototype.keys.call(fixedLength)), [
@@ -106,7 +106,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/Array/prototype/lastIndexOf/coerced-position-grow.js b/test/built-ins/Array/prototype/lastIndexOf/coerced-position-grow.js
index 76f95eed3f..f6dffe0110 100644
--- a/test/built-ins/Array/prototype/lastIndexOf/coerced-position-grow.js
+++ b/test/built-ins/Array/prototype/lastIndexOf/coerced-position-grow.js
@@ -10,19 +10,12 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 // Growing + length-tracking TA.
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, 1);
   }
   let evil = {
     valueOf: () => {
diff --git a/test/built-ins/Array/prototype/lastIndexOf/coerced-position-shrink.js b/test/built-ins/Array/prototype/lastIndexOf/coerced-position-shrink.js
index 13e07043b4..517530e0a8 100644
--- a/test/built-ins/Array/prototype/lastIndexOf/coerced-position-shrink.js
+++ b/test/built-ins/Array/prototype/lastIndexOf/coerced-position-shrink.js
@@ -10,13 +10,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 // Shrinking + fixed-length TA.
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
@@ -51,7 +44,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i);
   }
   let evil = {
     valueOf: () => {
diff --git a/test/built-ins/Array/prototype/lastIndexOf/resizable-buffer.js b/test/built-ins/Array/prototype/lastIndexOf/resizable-buffer.js
index 5e93b68598..686b09903b 100644
--- a/test/built-ins/Array/prototype/lastIndexOf/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/lastIndexOf/resizable-buffer.js
@@ -10,13 +10,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const fixedLength = new ctor(rab, 0, 4);
@@ -27,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, Math.floor(i / 2));
+    taWrite[i] = MayNeedBigInt(taWrite, Math.floor(i / 2));
   }
 
   // Orig. array: [0, 0, 1, 1]
@@ -104,7 +97,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, Math.floor(i / 2));
+    taWrite[i] = MayNeedBigInt(taWrite, Math.floor(i / 2));
   }
 
   // Orig. array: [0, 0, 1, 1, 2, 2]
diff --git a/test/built-ins/Array/prototype/map/resizable-buffer.js b/test/built-ins/Array/prototype/map/resizable-buffer.js
index e108395fcb..2fbef3500e 100644
--- a/test/built-ins/Array/prototype/map/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/map/resizable-buffer.js
@@ -19,7 +19,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < taWrite.length; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -105,7 +105,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/Array/prototype/reduce/resizable-buffer.js b/test/built-ins/Array/prototype/reduce/resizable-buffer.js
index c03585e3cd..9637a12e4f 100644
--- a/test/built-ins/Array/prototype/reduce/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/reduce/resizable-buffer.js
@@ -19,7 +19,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -90,7 +90,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/Array/prototype/reduceRight/resizable-buffer.js b/test/built-ins/Array/prototype/reduceRight/resizable-buffer.js
index a1fa69c6b0..7603636822 100644
--- a/test/built-ins/Array/prototype/reduceRight/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/reduceRight/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -93,7 +93,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/Array/prototype/reverse/resizable-buffer.js b/test/built-ins/Array/prototype/reverse/resizable-buffer.js
index f3b06228e7..e6a285d10f 100644
--- a/test/built-ins/Array/prototype/reverse/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/reverse/resizable-buffer.js
@@ -19,7 +19,7 @@ for (let ctor of ctors) {
   function WriteData() {
     // Write some data into the array.
     for (let i = 0; i < wholeArrayView.length; ++i) {
-      WriteToTypedArray(wholeArrayView, i, 2 * i);
+      wholeArrayView[i] = MayNeedBigInt(wholeArrayView, 2 * i);
     }
   }
   WriteData();
diff --git a/test/built-ins/Array/prototype/slice/coerced-start-end-grow.js b/test/built-ins/Array/prototype/slice/coerced-start-end-grow.js
index 2d718b803d..aff475886f 100644
--- a/test/built-ins/Array/prototype/slice/coerced-start-end-grow.js
+++ b/test/built-ins/Array/prototype/slice/coerced-start-end-grow.js
@@ -15,7 +15,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i + 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i + 1);
   }
   const evil = {
     valueOf: () => {
@@ -37,7 +37,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i + 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i + 1);
   }
 
   const evil = {
diff --git a/test/built-ins/Array/prototype/slice/coerced-start-end-shrink.js b/test/built-ins/Array/prototype/slice/coerced-start-end-shrink.js
index b6656b3be3..4786edaffc 100644
--- a/test/built-ins/Array/prototype/slice/coerced-start-end-shrink.js
+++ b/test/built-ins/Array/prototype/slice/coerced-start-end-shrink.js
@@ -34,7 +34,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i + 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i + 1);
   }
   const evil = {
     valueOf: () => {
@@ -76,7 +76,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i + 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i + 1);
   }
   const evil = {
     valueOf: () => {
diff --git a/test/built-ins/Array/prototype/slice/resizable-buffer.js b/test/built-ins/Array/prototype/slice/resizable-buffer.js
index 606a520101..059d5293a6 100644
--- a/test/built-ins/Array/prototype/slice/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/slice/resizable-buffer.js
@@ -19,7 +19,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
   const fixedLengthSlice = Array.prototype.slice.call(fixedLength);
   assert.compareArray(ToNumbers(fixedLengthSlice), [
diff --git a/test/built-ins/Array/prototype/some/resizable-buffer.js b/test/built-ins/Array/prototype/some/resizable-buffer.js
index 0bd06bc97e..3f38be8073 100644
--- a/test/built-ins/Array/prototype/some/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/some/resizable-buffer.js
@@ -19,7 +19,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -79,7 +79,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/Array/prototype/sort/comparefn-grow.js b/test/built-ins/Array/prototype/sort/comparefn-grow.js
index 640cdda2ae..7b2046490c 100644
--- a/test/built-ins/Array/prototype/sort/comparefn-grow.js
+++ b/test/built-ins/Array/prototype/sort/comparefn-grow.js
@@ -25,7 +25,7 @@ function ResizeAndCompare(rab, resizeTo) {
 
 function WriteUnsortedData(taFull) {
   for (let i = 0; i < taFull.length; ++i) {
-    WriteToTypedArray(taFull, i, 10 - i);
+    taFull[i] = MayNeedBigInt(taFull, 10 - i);
   }
 }
 
diff --git a/test/built-ins/Array/prototype/sort/comparefn-resizable-buffer.js b/test/built-ins/Array/prototype/sort/comparefn-resizable-buffer.js
index b575811e80..91d0f5b6ff 100644
--- a/test/built-ins/Array/prototype/sort/comparefn-resizable-buffer.js
+++ b/test/built-ins/Array/prototype/sort/comparefn-resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   function WriteUnsortedData() {
     // Write some data into the array.
     for (let i = 0; i < taFull.length; ++i) {
-      WriteToTypedArray(taFull, i, 10 - i);
+      taFull[i] = MayNeedBigInt(taFull, 10 - i);
     }
   }
   function OddBeforeEvenComparison(a, b) {
diff --git a/test/built-ins/Array/prototype/sort/comparefn-shrink.js b/test/built-ins/Array/prototype/sort/comparefn-shrink.js
index c9c26f01c6..2dd82e2c22 100644
--- a/test/built-ins/Array/prototype/sort/comparefn-shrink.js
+++ b/test/built-ins/Array/prototype/sort/comparefn-shrink.js
@@ -25,7 +25,7 @@ function ResizeAndCompare(rab, resizeTo) {
 
 function WriteUnsortedData(taFull) {
   for (let i = 0; i < taFull.length; ++i) {
-    WriteToTypedArray(taFull, i, 10 - i);
+    taFull[i] = MayNeedBigInt(taFull, 10 - i);
   }
 }
 
diff --git a/test/built-ins/Array/prototype/sort/resizable-buffer-default-comparator.js b/test/built-ins/Array/prototype/sort/resizable-buffer-default-comparator.js
index 38b1c065da..db3f71ca60 100644
--- a/test/built-ins/Array/prototype/sort/resizable-buffer-default-comparator.js
+++ b/test/built-ins/Array/prototype/sort/resizable-buffer-default-comparator.js
@@ -22,7 +22,7 @@ for (let ctor of ctors) {
   function WriteUnsortedData() {
     // Write some data into the array.
     for (let i = 0; i < taFull.length; ++i) {
-      WriteToTypedArray(taFull, i, 10 - 2 * i);
+      taFull[i] = MayNeedBigInt(taFull, 10 - 2 * i);
     }
   }
   // Orig. array: [10, 8, 6, 4]
diff --git a/test/built-ins/Array/prototype/toLocaleString/resizable-buffer.js b/test/built-ins/Array/prototype/toLocaleString/resizable-buffer.js
index c8768f47fe..e9b4b6add2 100644
--- a/test/built-ins/Array/prototype/toLocaleString/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/toLocaleString/resizable-buffer.js
@@ -26,7 +26,7 @@ for (let ctor of ctors) {
 
   // Write some data into the array.
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -72,7 +72,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/Array/prototype/values/resizable-buffer.js b/test/built-ins/Array/prototype/values/resizable-buffer.js
index c4b7f77868..c2d06cc9d1 100644
--- a/test/built-ins/Array/prototype/values/resizable-buffer.js
+++ b/test/built-ins/Array/prototype/values/resizable-buffer.js
@@ -27,7 +27,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -120,7 +120,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/Function/prototype/apply/resizable-buffer.js b/test/built-ins/Function/prototype/apply/resizable-buffer.js
index 2e93f387cb..2487870667 100644
--- a/test/built-ins/Function/prototype/apply/resizable-buffer.js
+++ b/test/built-ins/Function/prototype/apply/resizable-buffer.js
@@ -19,7 +19,7 @@ for (let ctor of ctors) {
   const lengthTrackingWithOffset = new ctor(rab, 2 * ctor.BYTES_PER_ELEMENT);
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
   function func(...args) {
     return [...args];
diff --git a/test/built-ins/Object/defineProperties/typedarray-backed-by-resizable-buffer.js b/test/built-ins/Object/defineProperties/typedarray-backed-by-resizable-buffer.js
index 46901a0874..fa3c597701 100644
--- a/test/built-ins/Object/defineProperties/typedarray-backed-by-resizable-buffer.js
+++ b/test/built-ins/Object/defineProperties/typedarray-backed-by-resizable-buffer.js
@@ -10,14 +10,6 @@ includes: [compareArray.js, resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, value) {
-  if (ta instanceof BigInt64Array || ta instanceof BigUint64Array) {
-    return BigInt(value);
-  } else {
-    return value;
-  }
-}
-
 function DefinePropertiesMayNeedBigInt(ta, index, value) {
   const values = {};
   values[index] = { value: MayNeedBigInt(ta, value) };
diff --git a/test/built-ins/Object/defineProperty/coerced-P-grow.js b/test/built-ins/Object/defineProperty/coerced-P-grow.js
index 106de77d25..9a84f8770c 100644
--- a/test/built-ins/Object/defineProperty/coerced-P-grow.js
+++ b/test/built-ins/Object/defineProperty/coerced-P-grow.js
@@ -11,14 +11,6 @@ includes: [compareArray.js, resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, value) {
-  if (ta instanceof BigInt64Array || ta instanceof BigUint64Array) {
-    return BigInt(value);
-  } else {
-    return value;
-  }
-}
-
 // Fixed length.
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
diff --git a/test/built-ins/Object/defineProperty/coerced-P-shrink.js b/test/built-ins/Object/defineProperty/coerced-P-shrink.js
index bcc3019d5a..55ac63ae47 100644
--- a/test/built-ins/Object/defineProperty/coerced-P-shrink.js
+++ b/test/built-ins/Object/defineProperty/coerced-P-shrink.js
@@ -11,14 +11,6 @@ includes: [compareArray.js, resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, value) {
-  if (ta instanceof BigInt64Array || ta instanceof BigUint64Array) {
-    return BigInt(value);
-  } else {
-    return value;
-  }
-}
-
 // Fixed length.
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
diff --git a/test/built-ins/Object/defineProperty/typedarray-backed-by-resizable-buffer.js b/test/built-ins/Object/defineProperty/typedarray-backed-by-resizable-buffer.js
index 155fd50445..9c031dc4ac 100644
--- a/test/built-ins/Object/defineProperty/typedarray-backed-by-resizable-buffer.js
+++ b/test/built-ins/Object/defineProperty/typedarray-backed-by-resizable-buffer.js
@@ -10,14 +10,6 @@ includes: [compareArray.js, resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, value) {
-  if (ta instanceof BigInt64Array || ta instanceof BigUint64Array) {
-    return BigInt(value);
-  } else {
-    return value;
-  }
-}
-
 function DefinePropertyMayNeedBigInt(ta, index, value) {
   Object.defineProperty(ta, index, { value: MayNeedBigInt(ta, value) });
 }
diff --git a/test/built-ins/TypedArray/out-of-bounds-get-and-set.js b/test/built-ins/TypedArray/out-of-bounds-get-and-set.js
index 5e3b59c49a..4d7019ae3a 100644
--- a/test/built-ins/TypedArray/out-of-bounds-get-and-set.js
+++ b/test/built-ins/TypedArray/out-of-bounds-get-and-set.js
@@ -10,14 +10,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, num) {
-  if (ta instanceof BigInt64Array || ta instanceof BigUint64Array) {
-    return BigInt(num);
-  } else {
-    return num;
-  }
-}
-
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 40 * ctor.BYTES_PER_ELEMENT);
   const array = new ctor(rab, 0, 4);
diff --git a/test/built-ins/TypedArray/prototype/at/resizable-buffer.js b/test/built-ins/TypedArray/prototype/at/resizable-buffer.js
index 6379e40332..9fea7397d0 100644
--- a/test/built-ins/TypedArray/prototype/at/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/at/resizable-buffer.js
@@ -24,7 +24,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   let ta_write = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(ta_write, i, i);
+    ta_write[i] = MayNeedBigInt(ta_write, i);
   }
   assert.sameValue(TypedArrayAtHelper(fixedLength, -1), 3);
   assert.sameValue(TypedArrayAtHelper(lengthTracking, -1), 3);
diff --git a/test/built-ins/TypedArray/prototype/copyWithin/coerced-target-start-end-shrink.js b/test/built-ins/TypedArray/prototype/copyWithin/coerced-target-start-end-shrink.js
index 34e5ea74d0..65270444ad 100644
--- a/test/built-ins/TypedArray/prototype/copyWithin/coerced-target-start-end-shrink.js
+++ b/test/built-ins/TypedArray/prototype/copyWithin/coerced-target-start-end-shrink.js
@@ -34,7 +34,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i);
   }
   // [0, 1, 2, 3]
   //        ^
@@ -58,7 +58,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i);
   }
   // [0, 1, 2, 3]
   //        ^
diff --git a/test/built-ins/TypedArray/prototype/copyWithin/coerced-target-start-grow.js b/test/built-ins/TypedArray/prototype/copyWithin/coerced-target-start-grow.js
index 6d1b3fc9d0..94495d35bd 100644
--- a/test/built-ins/TypedArray/prototype/copyWithin/coerced-target-start-grow.js
+++ b/test/built-ins/TypedArray/prototype/copyWithin/coerced-target-start-grow.js
@@ -13,13 +13,13 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i);
   }
   const evil = {
     valueOf: () => {
       rab.resize(6 * ctor.BYTES_PER_ELEMENT);
-      WriteToTypedArray(lengthTracking, 4, 4);
-      WriteToTypedArray(lengthTracking, 5, 5);
+      lengthTracking[4] = MayNeedBigInt(lengthTracking, 4);
+      lengthTracking[5] = MayNeedBigInt(lengthTracking, 5);
       return 0;
     }
   };
@@ -37,7 +37,7 @@ for (let ctor of ctors) {
   ]);
   rab.resize(4 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i);
   }
 
   // Orig. array: [0, 1, 2, 3]  [4, 5]
diff --git a/test/built-ins/TypedArray/prototype/copyWithin/resizable-buffer.js b/test/built-ins/TypedArray/prototype/copyWithin/resizable-buffer.js
index 7bd24ffc0b..d86049c04e 100644
--- a/test/built-ins/TypedArray/prototype/copyWithin/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/copyWithin/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   // Orig. array: [0, 1, 2, 3]
@@ -37,7 +37,7 @@ for (let ctor of ctors) {
     3
   ]);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
   fixedLengthWithOffset.copyWithin(0, 1);
   assert.compareArray(ToNumbers(fixedLengthWithOffset), [
@@ -45,7 +45,7 @@ for (let ctor of ctors) {
     3
   ]);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
   lengthTracking.copyWithin(0, 2);
   assert.compareArray(ToNumbers(lengthTracking), [
@@ -63,7 +63,7 @@ for (let ctor of ctors) {
   // Shrink so that fixed length TAs go out of bounds.
   rab.resize(3 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 3; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   // Orig. array: [0, 1, 2]
@@ -92,7 +92,7 @@ for (let ctor of ctors) {
 
   // Shrink so that the TAs with offset go out of bounds.
   rab.resize(1 * ctor.BYTES_PER_ELEMENT);
-  WriteToTypedArray(taWrite, 0, 0);
+  taWrite[0] = MayNeedBigInt(taWrite, 0);
   assert.throws(TypeError, () => {
     fixedLength.copyWithin(0, 1, 1);
   });
@@ -124,7 +124,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   // Orig. array: [0, 1, 2, 3, 4, 5]
@@ -141,7 +141,7 @@ for (let ctor of ctors) {
     3
   ]);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
   fixedLengthWithOffset.copyWithin(0, 1);
   assert.compareArray(ToNumbers(fixedLengthWithOffset), [
@@ -149,7 +149,7 @@ for (let ctor of ctors) {
     3
   ]);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   //              [0, 1, 2, 3, 4, 5, ...] << lengthTracking
@@ -164,7 +164,7 @@ for (let ctor of ctors) {
     5
   ]);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   //                    [2, 3, 4, 5, ...] << lengthTrackingWithOffset
diff --git a/test/built-ins/TypedArray/prototype/entries/resizable-buffer.js b/test/built-ins/TypedArray/prototype/entries/resizable-buffer.js
index a5fae1ba7b..1124bb2a6e 100644
--- a/test/built-ins/TypedArray/prototype/entries/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/entries/resizable-buffer.js
@@ -31,7 +31,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -140,7 +140,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArray/prototype/every/resizable-buffer.js b/test/built-ins/TypedArray/prototype/every/resizable-buffer.js
index 22369d6271..37140219f3 100644
--- a/test/built-ins/TypedArray/prototype/every/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/every/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -102,7 +102,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArray/prototype/filter/resizable-buffer.js b/test/built-ins/TypedArray/prototype/filter/resizable-buffer.js
index de536e2912..b0700f2ed3 100644
--- a/test/built-ins/TypedArray/prototype/filter/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/filter/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   // Orig. array: [0, 1, 2, 3]
@@ -94,7 +94,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
 
   // Orig. array: [0, 1, 2, 3, 4, 5]
diff --git a/test/built-ins/TypedArray/prototype/find/resizable-buffer.js b/test/built-ins/TypedArray/prototype/find/resizable-buffer.js
index 128f4c1140..98ac15257f 100644
--- a/test/built-ins/TypedArray/prototype/find/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/find/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -85,10 +85,10 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 0);
+    taWrite[i] = MayNeedBigInt(taWrite, 0);
   }
-  WriteToTypedArray(taWrite, 4, 2);
-  WriteToTypedArray(taWrite, 5, 4);
+  taWrite[4] = MayNeedBigInt(taWrite, 2);
+  taWrite[5] = MayNeedBigInt(taWrite, 4);
 
   // Orig. array: [0, 0, 0, 0, 2, 4]
   //              [0, 0, 0, 0] << fixedLength
diff --git a/test/built-ins/TypedArray/prototype/findIndex/resizable-buffer.js b/test/built-ins/TypedArray/prototype/findIndex/resizable-buffer.js
index 645ff3369a..ef2b768a2d 100644
--- a/test/built-ins/TypedArray/prototype/findIndex/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/findIndex/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -84,10 +84,10 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 0);
+    taWrite[i] = MayNeedBigInt(taWrite, 0);
   }
-  WriteToTypedArray(taWrite, 4, 2);
-  WriteToTypedArray(taWrite, 5, 4);
+  taWrite[4] = MayNeedBigInt(taWrite, 2);
+  taWrite[5] = MayNeedBigInt(taWrite, 4);
 
   // Orig. array: [0, 0, 0, 0, 2, 4]
   //              [0, 0, 0, 0] << fixedLength
diff --git a/test/built-ins/TypedArray/prototype/findLast/resizable-buffer.js b/test/built-ins/TypedArray/prototype/findLast/resizable-buffer.js
index 0b8bcc2044..7d842f18b2 100644
--- a/test/built-ins/TypedArray/prototype/findLast/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/findLast/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -85,10 +85,10 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 0);
+    taWrite[i] = MayNeedBigInt(taWrite, 0);
   }
-  WriteToTypedArray(taWrite, 4, 2);
-  WriteToTypedArray(taWrite, 5, 4);
+  taWrite[4] = MayNeedBigInt(taWrite, 2);
+  taWrite[5] = MayNeedBigInt(taWrite, 4);
 
   // Orig. array: [0, 0, 0, 0, 2, 4]
   //              [0, 0, 0, 0] << fixedLength
diff --git a/test/built-ins/TypedArray/prototype/findLastIndex/resizable-buffer.js b/test/built-ins/TypedArray/prototype/findLastIndex/resizable-buffer.js
index 3adf4d0ebb..0dad13566c 100644
--- a/test/built-ins/TypedArray/prototype/findLastIndex/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/findLastIndex/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -84,10 +84,10 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 0);
+    taWrite[i] = MayNeedBigInt(taWrite, 0);
   }
-  WriteToTypedArray(taWrite, 4, 2);
-  WriteToTypedArray(taWrite, 5, 4);
+  taWrite[4] = MayNeedBigInt(taWrite, 2);
+  taWrite[5] = MayNeedBigInt(taWrite, 4);
 
   // Orig. array: [0, 0, 0, 0, 2, 4]
   //              [0, 0, 0, 0] << fixedLength
diff --git a/test/built-ins/TypedArray/prototype/forEach/resizable-buffer.js b/test/built-ins/TypedArray/prototype/forEach/resizable-buffer.js
index 74ab29bb23..411ae267f4 100644
--- a/test/built-ins/TypedArray/prototype/forEach/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/forEach/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -109,7 +109,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArray/prototype/includes/coerced-searchelement-fromindex-resize.js b/test/built-ins/TypedArray/prototype/includes/coerced-searchelement-fromindex-resize.js
index 8fed6fec14..8eeced9cb9 100644
--- a/test/built-ins/TypedArray/prototype/includes/coerced-searchelement-fromindex-resize.js
+++ b/test/built-ins/TypedArray/prototype/includes/coerced-searchelement-fromindex-resize.js
@@ -10,13 +10,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer, Array.prototype.includes]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const fixedLength = new ctor(rab, 0, 4);
@@ -61,7 +54,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, 1);
   }
   let evil = {
     valueOf: () => {
@@ -77,7 +70,7 @@ for (let ctor of ctors) {
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
-  WriteToTypedArray(lengthTracking, 0, 1);
+  lengthTracking[0] = MayNeedBigInt(lengthTracking, 1);
   let evil = {
     valueOf: () => {
       rab.resize(6 * ctor.BYTES_PER_ELEMENT);
diff --git a/test/built-ins/TypedArray/prototype/includes/resizable-buffer.js b/test/built-ins/TypedArray/prototype/includes/resizable-buffer.js
index 8e99ce5db6..523422df22 100644
--- a/test/built-ins/TypedArray/prototype/includes/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/includes/resizable-buffer.js
@@ -10,13 +10,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer, Array.prototype.includes]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const fixedLength = new ctor(rab, 0, 4);
@@ -27,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -116,7 +109,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArray/prototype/indexOf/coerced-searchelement-fromindex-grow.js b/test/built-ins/TypedArray/prototype/indexOf/coerced-searchelement-fromindex-grow.js
index 7b63c5009c..f18ccf1a8c 100644
--- a/test/built-ins/TypedArray/prototype/indexOf/coerced-searchelement-fromindex-grow.js
+++ b/test/built-ins/TypedArray/prototype/indexOf/coerced-searchelement-fromindex-grow.js
@@ -10,19 +10,12 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 // Growing + length-tracking TA.
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, 1);
   }
   let evil = {
     valueOf: () => {
@@ -40,7 +33,7 @@ for (let ctor of ctors) {
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
-  WriteToTypedArray(lengthTracking, 0, 1);
+  lengthTracking[0] = MayNeedBigInt(lengthTracking, 1);
   let evil = {
     valueOf: () => {
       rab.resize(6 * ctor.BYTES_PER_ELEMENT);
diff --git a/test/built-ins/TypedArray/prototype/indexOf/coerced-searchelement-fromindex-shrink.js b/test/built-ins/TypedArray/prototype/indexOf/coerced-searchelement-fromindex-shrink.js
index befab22a27..6a2ffce3f2 100644
--- a/test/built-ins/TypedArray/prototype/indexOf/coerced-searchelement-fromindex-shrink.js
+++ b/test/built-ins/TypedArray/prototype/indexOf/coerced-searchelement-fromindex-shrink.js
@@ -10,13 +10,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 // Shrinking + fixed-length TA.
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
@@ -52,7 +45,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i);
   }
   let evil = {
     valueOf: () => {
diff --git a/test/built-ins/TypedArray/prototype/indexOf/resizable-buffer.js b/test/built-ins/TypedArray/prototype/indexOf/resizable-buffer.js
index 43519225f0..16398b4e76 100644
--- a/test/built-ins/TypedArray/prototype/indexOf/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/indexOf/resizable-buffer.js
@@ -10,13 +10,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const fixedLength = new ctor(rab, 0, 4);
@@ -27,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, Math.floor(i / 2));
+    taWrite[i] = MayNeedBigInt(taWrite, Math.floor(i / 2));
   }
 
   // Orig. array: [0, 0, 1, 1]
@@ -116,7 +109,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, Math.floor(i / 2));
+    taWrite[i] = MayNeedBigInt(taWrite, Math.floor(i / 2));
   }
 
   // Orig. array: [0, 0, 1, 1, 2, 2]
diff --git a/test/built-ins/TypedArray/prototype/join/resizable-buffer.js b/test/built-ins/TypedArray/prototype/join/resizable-buffer.js
index 02d96a4f0c..cbe3ca744b 100644
--- a/test/built-ins/TypedArray/prototype/join/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/join/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
 
   // Write some data into the array.
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -82,7 +82,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArray/prototype/keys/resizable-buffer.js b/test/built-ins/TypedArray/prototype/keys/resizable-buffer.js
index 694087c7e8..21a2d34ec9 100644
--- a/test/built-ins/TypedArray/prototype/keys/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/keys/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -105,7 +105,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArray/prototype/lastIndexOf/coerced-position-grow.js b/test/built-ins/TypedArray/prototype/lastIndexOf/coerced-position-grow.js
index 8ac8387581..504642dbc0 100644
--- a/test/built-ins/TypedArray/prototype/lastIndexOf/coerced-position-grow.js
+++ b/test/built-ins/TypedArray/prototype/lastIndexOf/coerced-position-grow.js
@@ -10,19 +10,12 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 // Growing + length-tracking TA.
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, 1);
   }
   let evil = {
     valueOf: () => {
diff --git a/test/built-ins/TypedArray/prototype/lastIndexOf/coerced-position-shrink.js b/test/built-ins/TypedArray/prototype/lastIndexOf/coerced-position-shrink.js
index 2879e776ed..ee5a88faa9 100644
--- a/test/built-ins/TypedArray/prototype/lastIndexOf/coerced-position-shrink.js
+++ b/test/built-ins/TypedArray/prototype/lastIndexOf/coerced-position-shrink.js
@@ -10,13 +10,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 // Shrinking + fixed-length TA.
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
@@ -52,7 +45,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i);
   }
   let evil = {
     valueOf: () => {
diff --git a/test/built-ins/TypedArray/prototype/lastIndexOf/resizable-buffer.js b/test/built-ins/TypedArray/prototype/lastIndexOf/resizable-buffer.js
index bba8d75a97..4b2ac4536d 100644
--- a/test/built-ins/TypedArray/prototype/lastIndexOf/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/lastIndexOf/resizable-buffer.js
@@ -10,13 +10,6 @@ includes: [resizableArrayBufferUtils.js]
 features: [resizable-arraybuffer]
 ---*/
 
-function MayNeedBigInt(ta, n) {
-  if (typeof n == 'number' && (ta instanceof BigInt64Array || ta instanceof BigUint64Array)) {
-    return BigInt(n);
-  }
-  return n;
-}
-
 for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const fixedLength = new ctor(rab, 0, 4);
@@ -27,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, Math.floor(i / 2));
+    taWrite[i] = MayNeedBigInt(taWrite, Math.floor(i / 2));
   }
 
   // Orig. array: [0, 0, 1, 1]
@@ -120,7 +113,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, Math.floor(i / 2));
+    taWrite[i] = MayNeedBigInt(taWrite, Math.floor(i / 2));
   }
 
   // Orig. array: [0, 0, 1, 1, 2, 2]
diff --git a/test/built-ins/TypedArray/prototype/map/resizable-buffer.js b/test/built-ins/TypedArray/prototype/map/resizable-buffer.js
index 24c7cf1bb4..1f01829b16 100644
--- a/test/built-ins/TypedArray/prototype/map/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/map/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < taWrite.length; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -122,7 +122,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArray/prototype/map/speciesctor-resizable-buffer-grow.js b/test/built-ins/TypedArray/prototype/map/speciesctor-resizable-buffer-grow.js
index d9999cb8a2..bc17496648 100644
--- a/test/built-ins/TypedArray/prototype/map/speciesctor-resizable-buffer-grow.js
+++ b/test/built-ins/TypedArray/prototype/map/speciesctor-resizable-buffer-grow.js
@@ -32,7 +32,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
   let resizeWhenConstructorCalled = false;
   class MyArray extends ctor {
@@ -59,7 +59,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
   let resizeWhenConstructorCalled = false;
   class MyArray extends ctor {
diff --git a/test/built-ins/TypedArray/prototype/map/speciesctor-resizable-buffer-shrink.js b/test/built-ins/TypedArray/prototype/map/speciesctor-resizable-buffer-shrink.js
index 7b4e47d99a..50e43622f5 100644
--- a/test/built-ins/TypedArray/prototype/map/speciesctor-resizable-buffer-shrink.js
+++ b/test/built-ins/TypedArray/prototype/map/speciesctor-resizable-buffer-shrink.js
@@ -56,7 +56,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
   let resizeWhenConstructorCalled = false;
   class MyArray extends ctor {
diff --git a/test/built-ins/TypedArray/prototype/reduce/resizable-buffer.js b/test/built-ins/TypedArray/prototype/reduce/resizable-buffer.js
index 4956887d17..6891e9423b 100644
--- a/test/built-ins/TypedArray/prototype/reduce/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/reduce/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -109,7 +109,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArray/prototype/reduceRight/resizable-buffer.js b/test/built-ins/TypedArray/prototype/reduceRight/resizable-buffer.js
index a3c2770c06..305b072ba7 100644
--- a/test/built-ins/TypedArray/prototype/reduceRight/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/reduceRight/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -110,7 +110,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArray/prototype/reverse/resizable-buffer.js b/test/built-ins/TypedArray/prototype/reverse/resizable-buffer.js
index 7c30bb0c1b..ec0162b3a4 100644
--- a/test/built-ins/TypedArray/prototype/reverse/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/reverse/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   function WriteData() {
     // Write some data into the array.
     for (let i = 0; i < wholeArrayView.length; ++i) {
-      WriteToTypedArray(wholeArrayView, i, 2 * i);
+      wholeArrayView[i] = MayNeedBigInt(wholeArrayView, 2 * i);
     }
   }
   WriteData();
diff --git a/test/built-ins/TypedArray/prototype/set/typedarray-arg-src-backed-by-resizable-buffer.js b/test/built-ins/TypedArray/prototype/set/typedarray-arg-src-backed-by-resizable-buffer.js
index 79aba4fb70..b11b759e6c 100644
--- a/test/built-ins/TypedArray/prototype/set/typedarray-arg-src-backed-by-resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/set/typedarray-arg-src-backed-by-resizable-buffer.js
@@ -42,7 +42,7 @@ for (let targetIsResizable of [
       // Write some data into the array.
       const taFull = new sourceCtor(rab);
       for (let i = 0; i < 4; ++i) {
-        WriteToTypedArray(taFull, i, i + 1);
+        taFull[i] = MayNeedBigInt(taFull, i + 1);
       }
 
       // Orig. array: [1, 2, 3, 4]
@@ -179,7 +179,7 @@ for (let targetIsResizable of [
       // Grow so that all TAs are back in-bounds.
       rab.resize(6 * sourceCtor.BYTES_PER_ELEMENT);
       for (let i = 0; i < 6; ++i) {
-        WriteToTypedArray(taFull, i, i + 1);
+        taFull[i] = MayNeedBigInt(taFull, i + 1);
       }
 
       // Orig. array: [1, 2, 3, 4, 5, 6]
diff --git a/test/built-ins/TypedArray/prototype/slice/coerced-start-end-grow.js b/test/built-ins/TypedArray/prototype/slice/coerced-start-end-grow.js
index 4a927dd8aa..48cb09eb19 100644
--- a/test/built-ins/TypedArray/prototype/slice/coerced-start-end-grow.js
+++ b/test/built-ins/TypedArray/prototype/slice/coerced-start-end-grow.js
@@ -15,7 +15,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i + 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i + 1);
   }
   const evil = {
     valueOf: () => {
@@ -37,7 +37,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i + 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i + 1);
   }
   const evil = {
     valueOf: () => {
diff --git a/test/built-ins/TypedArray/prototype/slice/coerced-start-end-shrink.js b/test/built-ins/TypedArray/prototype/slice/coerced-start-end-shrink.js
index 1359f8ba34..750a78ca97 100644
--- a/test/built-ins/TypedArray/prototype/slice/coerced-start-end-shrink.js
+++ b/test/built-ins/TypedArray/prototype/slice/coerced-start-end-shrink.js
@@ -29,7 +29,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i + 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i + 1);
   }
   const evil = {
     valueOf: () => {
@@ -69,7 +69,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const lengthTracking = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(lengthTracking, i, i + 1);
+    lengthTracking[i] = MayNeedBigInt(lengthTracking, i + 1);
   }
   const evil = {
     valueOf: () => {
diff --git a/test/built-ins/TypedArray/prototype/slice/resizable-buffer.js b/test/built-ins/TypedArray/prototype/slice/resizable-buffer.js
index db072bf3d5..cc92b2f616 100644
--- a/test/built-ins/TypedArray/prototype/slice/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/slice/resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, i);
+    taWrite[i] = MayNeedBigInt(taWrite, i);
   }
   const fixedLengthSlice = fixedLength.slice();
   assert.compareArray(ToNumbers(fixedLengthSlice), [
diff --git a/test/built-ins/TypedArray/prototype/slice/speciesctor-resize.js b/test/built-ins/TypedArray/prototype/slice/speciesctor-resize.js
index 280d8a3c13..2da4d2a531 100644
--- a/test/built-ins/TypedArray/prototype/slice/speciesctor-resize.js
+++ b/test/built-ins/TypedArray/prototype/slice/speciesctor-resize.js
@@ -36,7 +36,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 1);
+    taWrite[i] = MayNeedBigInt(taWrite, 1);
   }
   let resizeWhenConstructorCalled = false;
   class MyArray extends ctor {
@@ -69,7 +69,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(4 * ctor.BYTES_PER_ELEMENT, 8 * ctor.BYTES_PER_ELEMENT);
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 1);
+    taWrite[i] = MayNeedBigInt(taWrite, 1);
   }
   let resizeWhenConstructorCalled = false;
   class MyArray extends ctor {
@@ -99,7 +99,7 @@ for (let ctor of ctors) {
   const rab = CreateResizableArrayBuffer(8, 16);
   const taWrite = new Uint8Array(rab);
   for (let i = 0; i < 8; ++i) {
-    WriteToTypedArray(taWrite, i, 255);
+    taWrite[i] = MayNeedBigInt(taWrite, 255);
   }
   let resizeWhenConstructorCalled = false;
   class MyArray extends Uint16Array {
diff --git a/test/built-ins/TypedArray/prototype/some/resizable-buffer.js b/test/built-ins/TypedArray/prototype/some/resizable-buffer.js
index 6a4c08b55d..dcb57bac93 100644
--- a/test/built-ins/TypedArray/prototype/some/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/some/resizable-buffer.js
@@ -19,7 +19,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -95,7 +95,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArray/prototype/sort/comparefn-grow.js b/test/built-ins/TypedArray/prototype/sort/comparefn-grow.js
index 11f09bf467..8a54fbd01b 100644
--- a/test/built-ins/TypedArray/prototype/sort/comparefn-grow.js
+++ b/test/built-ins/TypedArray/prototype/sort/comparefn-grow.js
@@ -27,7 +27,7 @@ function ResizeAndCompare(rab, resizeTo) {
 
 function WriteUnsortedData(taFull) {
   for (let i = 0; i < taFull.length; ++i) {
-    WriteToTypedArray(taFull, i, 10 - i);
+    taFull[i] = MayNeedBigInt(taFull, 10 - i);
   }
 }
 
diff --git a/test/built-ins/TypedArray/prototype/sort/comparefn-resizable-buffer.js b/test/built-ins/TypedArray/prototype/sort/comparefn-resizable-buffer.js
index c3c8c93371..ded426ff1d 100644
--- a/test/built-ins/TypedArray/prototype/sort/comparefn-resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/sort/comparefn-resizable-buffer.js
@@ -20,7 +20,7 @@ for (let ctor of ctors) {
   function WriteUnsortedData() {
     // Write some data into the array.
     for (let i = 0; i < taFull.length; ++i) {
-      WriteToTypedArray(taFull, i, 10 - i);
+      taFull[i] = MayNeedBigInt(taFull, 10 - i);
     }
   }
   function OddBeforeEvenComparison(a, b) {
diff --git a/test/built-ins/TypedArray/prototype/sort/comparefn-shrink.js b/test/built-ins/TypedArray/prototype/sort/comparefn-shrink.js
index b057179066..1daf665b9b 100644
--- a/test/built-ins/TypedArray/prototype/sort/comparefn-shrink.js
+++ b/test/built-ins/TypedArray/prototype/sort/comparefn-shrink.js
@@ -27,7 +27,7 @@ function ResizeAndCompare(rab, resizeTo) {
 
 function WriteUnsortedData(taFull) {
   for (let i = 0; i < taFull.length; ++i) {
-    WriteToTypedArray(taFull, i, 10 - i);
+    taFull[i] = MayNeedBigInt(taFull, 10 - i);
   }
 }
 
diff --git a/test/built-ins/TypedArray/prototype/sort/resizable-buffer-default-comparator.js b/test/built-ins/TypedArray/prototype/sort/resizable-buffer-default-comparator.js
index f3386199bd..a72343d783 100644
--- a/test/built-ins/TypedArray/prototype/sort/resizable-buffer-default-comparator.js
+++ b/test/built-ins/TypedArray/prototype/sort/resizable-buffer-default-comparator.js
@@ -22,7 +22,7 @@ for (let ctor of ctors) {
   function WriteUnsortedData() {
     // Write some data into the array.
     for (let i = 0; i < taFull.length; ++i) {
-      WriteToTypedArray(taFull, i, 10 - 2 * i);
+      taFull[i] = MayNeedBigInt(taFull, 10 - 2 * i);
     }
   }
   // Orig. array: [10, 8, 6, 4]
diff --git a/test/built-ins/TypedArray/prototype/subarray/resizable-buffer.js b/test/built-ins/TypedArray/prototype/subarray/resizable-buffer.js
index d740f26b52..6b0e4fc5cd 100644
--- a/test/built-ins/TypedArray/prototype/subarray/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/subarray/resizable-buffer.js
@@ -19,7 +19,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -129,7 +129,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArray/prototype/toLocaleString/resizable-buffer.js b/test/built-ins/TypedArray/prototype/toLocaleString/resizable-buffer.js
index d31c5f5a5b..0cb4161acc 100644
--- a/test/built-ins/TypedArray/prototype/toLocaleString/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/toLocaleString/resizable-buffer.js
@@ -36,7 +36,7 @@ for (let ctor of ctors) {
 
   // Write some data into the array.
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -98,7 +98,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArray/prototype/values/resizable-buffer.js b/test/built-ins/TypedArray/prototype/values/resizable-buffer.js
index e7eb2347ac..55dfc162ab 100644
--- a/test/built-ins/TypedArray/prototype/values/resizable-buffer.js
+++ b/test/built-ins/TypedArray/prototype/values/resizable-buffer.js
@@ -28,7 +28,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   const taWrite = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6]
@@ -113,7 +113,7 @@ for (let ctor of ctors) {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * ctor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taWrite, i, 2 * i);
+    taWrite[i] = MayNeedBigInt(taWrite, 2 * i);
   }
 
   // Orig. array: [0, 2, 4, 6, 8, 10]
diff --git a/test/built-ins/TypedArrayConstructors/ctors/typedarray-arg/src-typedarray-resizable-buffer.js b/test/built-ins/TypedArrayConstructors/ctors/typedarray-arg/src-typedarray-resizable-buffer.js
index 924d3e8943..c5bbd3ee6a 100644
--- a/test/built-ins/TypedArrayConstructors/ctors/typedarray-arg/src-typedarray-resizable-buffer.js
+++ b/test/built-ins/TypedArrayConstructors/ctors/typedarray-arg/src-typedarray-resizable-buffer.js
@@ -35,7 +35,7 @@ AllBigIntMatchedCtorCombinations((targetCtor, sourceCtor) => {
   // Write some data into the array.
   const taFull = new sourceCtor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(taFull, i, i + 1);
+    taFull[i] = MayNeedBigInt(taFull, i + 1);
   }
 
   // Orig. array: [1, 2, 3, 4]
@@ -114,7 +114,7 @@ AllBigIntMatchedCtorCombinations((targetCtor, sourceCtor) => {
   // Grow so that all TAs are back in-bounds.
   rab.resize(6 * sourceCtor.BYTES_PER_ELEMENT);
   for (let i = 0; i < 6; ++i) {
-    WriteToTypedArray(taFull, i, i + 1);
+    taFull[i] = MayNeedBigInt(taFull, i + 1);
   }
 
   // Orig. array: [1, 2, 3, 4, 5, 6]
diff --git a/test/language/destructuring/binding/typedarray-backed-by-resizable-buffer.js b/test/language/destructuring/binding/typedarray-backed-by-resizable-buffer.js
index 13e4df0221..7eb24f2b0e 100644
--- a/test/language/destructuring/binding/typedarray-backed-by-resizable-buffer.js
+++ b/test/language/destructuring/binding/typedarray-backed-by-resizable-buffer.js
@@ -19,7 +19,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   let ta_write = new ctor(rab);
   for (let i = 0; i < 4; ++i) {
-    WriteToTypedArray(ta_write, i, i);
+    ta_write[i] = MayNeedBigInt(ta_write, i);
   }
   {
     let [a, b, c, d, e] = fixedLength;
diff --git a/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-grow-before-end.js b/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-grow-before-end.js
index e8b56e2510..c9b5108e46 100644
--- a/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-grow-before-end.js
+++ b/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-grow-before-end.js
@@ -14,7 +14,7 @@ function CreateRab(buffer_byte_length, ctor) {
   const rab = CreateResizableArrayBuffer(buffer_byte_length, 2 * buffer_byte_length);
   let ta_write = new ctor(rab);
   for (let i = 0; i < buffer_byte_length / ctor.BYTES_PER_ELEMENT; ++i) {
-    WriteToTypedArray(ta_write, i, i % 128);
+    ta_write[i] = MayNeedBigInt(ta_write, i % 128);
   }
   return rab;
 }
diff --git a/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-grow-mid-iteration.js b/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-grow-mid-iteration.js
index 243c67dd9e..11e0017924 100644
--- a/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-grow-mid-iteration.js
+++ b/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-grow-mid-iteration.js
@@ -14,7 +14,7 @@ function CreateRab(buffer_byte_length, ctor) {
   const rab = CreateResizableArrayBuffer(buffer_byte_length, 2 * buffer_byte_length);
   let ta_write = new ctor(rab);
   for (let i = 0; i < buffer_byte_length / ctor.BYTES_PER_ELEMENT; ++i) {
-    WriteToTypedArray(ta_write, i, i % 128);
+    ta_write[i] = MayNeedBigInt(ta_write, i % 128);
   }
   return rab;
 }
diff --git a/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-shrink-mid-iteration.js b/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-shrink-mid-iteration.js
index 53cf49f967..a4862fd5c6 100644
--- a/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-shrink-mid-iteration.js
+++ b/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-shrink-mid-iteration.js
@@ -14,7 +14,7 @@ function CreateRab(buffer_byte_length, ctor) {
   const rab = CreateResizableArrayBuffer(buffer_byte_length, 2 * buffer_byte_length);
   let ta_write = new ctor(rab);
   for (let i = 0; i < buffer_byte_length / ctor.BYTES_PER_ELEMENT; ++i) {
-    WriteToTypedArray(ta_write, i, i % 128);
+    ta_write[i] = MayNeedBigInt(ta_write, i % 128);
   }
   return rab;
 }
diff --git a/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-shrink-to-zero-mid-iteration.js b/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-shrink-to-zero-mid-iteration.js
index 05393f707d..061b2e0ef8 100644
--- a/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-shrink-to-zero-mid-iteration.js
+++ b/test/language/statements/for-of/typedarray-backed-by-resizable-buffer-shrink-to-zero-mid-iteration.js
@@ -14,7 +14,7 @@ function CreateRab(buffer_byte_length, ctor) {
   const rab = CreateResizableArrayBuffer(buffer_byte_length, 2 * buffer_byte_length);
   let ta_write = new ctor(rab);
   for (let i = 0; i < buffer_byte_length / ctor.BYTES_PER_ELEMENT; ++i) {
-    WriteToTypedArray(ta_write, i, i % 128);
+    ta_write[i] = MayNeedBigInt(ta_write, i % 128);
   }
   return rab;
 }
diff --git a/test/language/statements/for-of/typedarray-backed-by-resizable-buffer.js b/test/language/statements/for-of/typedarray-backed-by-resizable-buffer.js
index fcdfab5cee..4d94f3badb 100644
--- a/test/language/statements/for-of/typedarray-backed-by-resizable-buffer.js
+++ b/test/language/statements/for-of/typedarray-backed-by-resizable-buffer.js
@@ -28,7 +28,7 @@ for (let ctor of ctors) {
   // Write some data into the array.
   let ta_write = new ctor(rab);
   for (let i = 0; i < no_elements; ++i) {
-    WriteToTypedArray(ta_write, i, i % 128);
+    ta_write[i] = MayNeedBigInt(ta_write, i % 128);
   }
 
   // Create various different styles of TypedArrays with the RAB as the