diff --git a/test/harness/assert-throws-same-realm.js b/test/harness/assert-throws-same-realm.js
index 17f0443112..b21273900e 100644
--- a/test/harness/assert-throws-same-realm.js
+++ b/test/harness/assert-throws-same-realm.js
@@ -4,7 +4,7 @@
 /*---
 description: >
     Functions that throw instances of the realm specified constructor function
-    satisfy the assertion, without cross realms collisions.
+    do not satisfy the assertion with cross realms collisions.
 ---*/
 
 var intrinsicTypeError = TypeError; 
diff --git a/test/harness/asyncHelpers-asyncTest-func-throws-sync.js b/test/harness/asyncHelpers-asyncTest-func-throws-sync.js
index f24b59b1ec..b3bdd7c373 100644
--- a/test/harness/asyncHelpers-asyncTest-func-throws-sync.js
+++ b/test/harness/asyncHelpers-asyncTest-func-throws-sync.js
@@ -6,11 +6,13 @@ description: |
 includes: [asyncHelpers.js]
 ---*/
 var called = false;
+var msg = "Should not be rethrown";
 function $DONE(error) {
   called = true;
   assert(error instanceof Test262Error);
+  assert.sameValue(error.message, msg, "Should report correct error");
 }
 asyncTest(function () {
-  throw new Test262Error("Should not be rethrown");
+  throw new Test262Error(msg);
 });
 assert(called, "asyncTest called $DONE with a synchronously thrown error");
diff --git a/test/harness/asyncHelpers-asyncTest-return-not-thenable.js b/test/harness/asyncHelpers-asyncTest-return-not-thenable.js
index 6a47de994e..e7a0a2c0b5 100644
--- a/test/harness/asyncHelpers-asyncTest-return-not-thenable.js
+++ b/test/harness/asyncHelpers-asyncTest-return-not-thenable.js
@@ -8,6 +8,7 @@ includes: [asyncHelpers.js, compareArray.js]
 
 const doneValues = [];
 function $DONE(error) {
+  // Will be a TypeError from trying to invoke .then() on non-thenable
   doneValues.push(error instanceof TypeError);
 }
 asyncTest(function () {
diff --git a/test/harness/asyncHelpers-asyncTest-returns-undefined.js b/test/harness/asyncHelpers-asyncTest-returns-undefined.js
index 78a6ebab76..b318be3823 100644
--- a/test/harness/asyncHelpers-asyncTest-returns-undefined.js
+++ b/test/harness/asyncHelpers-asyncTest-returns-undefined.js
@@ -2,7 +2,7 @@
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
 description: |
-    The 'asyncTest' helper when called with async flag always returns to undefined.
+    The 'asyncTest' helper when called with async flag always returns undefined.
 flags: [async]
 includes: [asyncHelpers.js]
 ---*/
diff --git a/test/harness/asyncHelpers-asyncTest-without-async-flag.js b/test/harness/asyncHelpers-asyncTest-without-async-flag.js
index d3eb5a07d1..f620a7d10e 100644
--- a/test/harness/asyncHelpers-asyncTest-without-async-flag.js
+++ b/test/harness/asyncHelpers-asyncTest-without-async-flag.js
@@ -8,7 +8,8 @@ includes: [asyncHelpers.js]
 function makePromise() {
   return {
     then(res, rej) {
-      throw new Test262Error("Should not be evaluated");
+      // Throw a different error than Test262Error to avoid confusion about what is rejecting
+      throw new Error("Should not be evaluated");
     },
   };
 }
diff --git a/test/harness/asyncHelpers-throwsAsync-custom-typeerror.js b/test/harness/asyncHelpers-throwsAsync-custom-typeerror.js
index 0f5cf43354..e048c1d1f2 100644
--- a/test/harness/asyncHelpers-throwsAsync-custom-typeerror.js
+++ b/test/harness/asyncHelpers-throwsAsync-custom-typeerror.js
@@ -10,7 +10,7 @@ includes: [asyncHelpers.js]
 
 var intrinsicTypeError = TypeError;
 
-(async function () {
+asyncTest(async function () {
   function TypeError() {}
   var caught = false;
 
@@ -69,4 +69,4 @@ var intrinsicTypeError = TypeError;
       "assert.throwsAsync did not reject a collision of constructor names"
     );
   }
-})().then($DONE, $DONE);
+})
diff --git a/test/harness/asyncHelpers-throwsAsync-custom.js b/test/harness/asyncHelpers-throwsAsync-custom.js
index 70a3f74a38..18c60f68bb 100644
--- a/test/harness/asyncHelpers-throwsAsync-custom.js
+++ b/test/harness/asyncHelpers-throwsAsync-custom.js
@@ -10,10 +10,10 @@ includes: [asyncHelpers.js]
 
 function MyError() {}
 
-(async function () {
+asyncTest(async function () {
   const p = assert.throwsAsync(MyError, function () {
     return Promise.reject(new MyError());
   });
   assert(p instanceof Promise);
   await p;
-})().then($DONE, $DONE);
+});
diff --git a/test/harness/asyncHelpers-throwsAsync-funcOrThenable-throws-sync.js b/test/harness/asyncHelpers-throwsAsync-func-throws-sync.js
similarity index 58%
rename from test/harness/asyncHelpers-throwsAsync-funcOrThenable-throws-sync.js
rename to test/harness/asyncHelpers-throwsAsync-func-throws-sync.js
index accad26ea6..379d6cc546 100644
--- a/test/harness/asyncHelpers-throwsAsync-funcOrThenable-throws-sync.js
+++ b/test/harness/asyncHelpers-throwsAsync-func-throws-sync.js
@@ -2,14 +2,14 @@
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
 description: |
-    assert.throwsAsync returns a promise that rejects if funcOrThenable or the inner thenable synchronously throws.
+    assert.throwsAsync returns a promise that rejects if func or the inner thenable synchronously throws.
 flags: [async]
 includes: [asyncHelpers.js]
 ---*/
 
-async function checkRejects(funcOrThenable) {
+async function checkRejects(func) {
   var caught = false;
-  const p = assert.throwsAsync(Test262Error, funcOrThenable);
+  const p = assert.throwsAsync(Test262Error, func);
   assert(p instanceof Promise, "assert.throwsAsync should return a promise");
   try {
     await p;
@@ -18,34 +18,23 @@ async function checkRejects(funcOrThenable) {
     assert.sameValue(
       e.constructor,
       Test262Error,
-      "throwsAsync should reject improper funcOrThenable with a Test262Error"
+      "throwsAsync should reject improper function with a Test262Error"
     );
   } finally {
     assert(
       caught,
-      "assert.throwsAsync did not reject improper funcOrThenable " +
-        funcOrThenable
+      "assert.throwsAsync did not reject improper function " + func
     );
   }
 }
 
-(async function () {
+asyncTest(async function () {
   await checkRejects(function () {
     throw new Error();
   });
   await checkRejects(function () {
     throw new Test262Error();
   });
-  await checkRejects({
-    then: function () {
-      throw new Error();
-    },
-  });
-  await checkRejects({
-    then: function () {
-      throw new Test262Error();
-    },
-  });
   await checkRejects(function () {
     return {
       then: function () {
@@ -60,4 +49,4 @@ async function checkRejects(funcOrThenable) {
       },
     };
   });
-})().then($DONE, $DONE);
+});
diff --git a/test/harness/asyncHelpers-throwsAsync-incorrect-ctor.js b/test/harness/asyncHelpers-throwsAsync-incorrect-ctor.js
index 62b30b138d..22eee7dfe6 100644
--- a/test/harness/asyncHelpers-throwsAsync-incorrect-ctor.js
+++ b/test/harness/asyncHelpers-throwsAsync-incorrect-ctor.js
@@ -8,7 +8,7 @@ flags: [async]
 includes: [asyncHelpers.js]
 ---*/
 
-(async function () {
+asyncTest(async function () {
   var caught = false;
 
   const p = assert.throwsAsync(Error, function () {
@@ -32,4 +32,4 @@ includes: [asyncHelpers.js]
       "assert.throwsAsync did not reject when a value with incorrect constructor was thrown"
     );
   }
-})().then($DONE, $DONE);
+});
diff --git a/test/harness/asyncHelpers-throwsAsync-invalid-funcOrThenable.js b/test/harness/asyncHelpers-throwsAsync-invalid-func.js
similarity index 65%
rename from test/harness/asyncHelpers-throwsAsync-invalid-funcOrThenable.js
rename to test/harness/asyncHelpers-throwsAsync-invalid-func.js
index 6b5156807c..c7406df012 100644
--- a/test/harness/asyncHelpers-throwsAsync-invalid-funcOrThenable.js
+++ b/test/harness/asyncHelpers-throwsAsync-invalid-func.js
@@ -2,14 +2,14 @@
 // This code is governed by the BSD license found in the LICENSE file.
 /*---
 description: |
-    assert.throwsAsync returns a promise that rejects if funcOrThenable is not a function returning a thenable or a thenable.
+    assert.throwsAsync calls $DONE with a rejecting value if func is not a function returning a thenable.
 flags: [async]
 includes: [asyncHelpers.js]
 ---*/
 
-async function checkRejects(funcOrThenable) {
+async function checkRejects(func) {
   var caught = false;
-  const p = assert.throwsAsync(Test262Error, funcOrThenable);
+  const p = assert.throwsAsync(Test262Error, func);
   assert(p instanceof Promise, "assert.throwsAsync should return a promise");
   try {
     await p;
@@ -18,28 +18,27 @@ async function checkRejects(funcOrThenable) {
     assert.sameValue(
       e.constructor,
       Test262Error,
-      "throwsAsync should reject improper funcOrThenable with a Test262Error"
+      "throwsAsync should reject improper function with a Test262Error"
     );
   } finally {
     assert(
       caught,
-      "assert.throwsAsync did not reject improper funcOrThenable " +
-        funcOrThenable
+      "assert.throwsAsync did not reject improper function " + func
     );
   }
 }
 
-(async function () {
+asyncTest(async function () {
   await checkRejects(null);
   await checkRejects({});
   await checkRejects("string");
   await checkRejects(10);
   await checkRejects();
-  await checkRejects({ then: null });
-  await checkRejects({ then: {} });
-  await checkRejects({ then: "string" });
-  await checkRejects({ then: 10 });
-  await checkRejects({ then: undefined });
+  await checkRejects({
+    then: function (res, rej) {
+      res(true);
+    },
+  });
   await checkRejects(function () {
     return null;
   });
@@ -68,4 +67,4 @@ async function checkRejects(funcOrThenable) {
   await checkRejects(function () {
     return { then: undefined };
   });
-})().then($DONE, $DONE);
+});
diff --git a/test/harness/asyncHelpers-throwsAsync-native.js b/test/harness/asyncHelpers-throwsAsync-native.js
index 08e416a18c..843bd4ea2a 100644
--- a/test/harness/asyncHelpers-throwsAsync-native.js
+++ b/test/harness/asyncHelpers-throwsAsync-native.js
@@ -8,7 +8,7 @@ flags: [async]
 includes: [asyncHelpers.js]
 ---*/
 
-(async function () {
+asyncTest(async function () {
   var p = assert.throwsAsync(Error, async function () {
     throw new Error();
   });
@@ -44,4 +44,4 @@ includes: [asyncHelpers.js]
   });
   assert(p instanceof Promise);
   await p;
-})().then($DONE, $DONE);
+});
diff --git a/test/harness/asyncHelpers-throwsAsync-no-arg.js b/test/harness/asyncHelpers-throwsAsync-no-arg.js
index b51b94345d..378bf962fb 100644
--- a/test/harness/asyncHelpers-throwsAsync-no-arg.js
+++ b/test/harness/asyncHelpers-throwsAsync-no-arg.js
@@ -7,7 +7,7 @@ flags: [async]
 includes: [asyncHelpers.js]
 ---*/
 
-(async function () {
+asyncTest(async function () {
   var caught = false;
 
   const p = assert.throwsAsync();
@@ -29,4 +29,4 @@ includes: [asyncHelpers.js]
       "assert.throwsAsync did not reject when invoked without arguments"
     );
   }
-})().then($DONE, $DONE);
+});
diff --git a/test/harness/asyncHelpers-throwsAsync-no-error.js b/test/harness/asyncHelpers-throwsAsync-no-error.js
index 97f9f3f3c1..cef530c25a 100644
--- a/test/harness/asyncHelpers-throwsAsync-no-error.js
+++ b/test/harness/asyncHelpers-throwsAsync-no-error.js
@@ -7,7 +7,7 @@ flags: [async]
 includes: [asyncHelpers.js]
 ---*/
 
-(async function () {
+asyncTest(async function () {
   var caught = false;
 
   const p = assert.throwsAsync(Error, async function () {});
@@ -29,4 +29,4 @@ includes: [asyncHelpers.js]
       "assert.throwsAsync did not reject when the thenable did not reject"
     );
   }
-})().then($DONE, $DONE);
+});
diff --git a/test/harness/asyncHelpers-throwsAsync-null.js b/test/harness/asyncHelpers-throwsAsync-null.js
index 3ab1d36d51..118f80eef1 100644
--- a/test/harness/asyncHelpers-throwsAsync-null.js
+++ b/test/harness/asyncHelpers-throwsAsync-null.js
@@ -7,7 +7,7 @@ flags: [async]
 includes: [asyncHelpers.js]
 ---*/
 
-(async function () {
+asyncTest(async function () {
   var caught = false;
 
   const p = assert.throwsAsync(Error, async function () {
@@ -31,4 +31,4 @@ includes: [asyncHelpers.js]
       "assert.throwsAsync did not reject when null was thrown"
     );
   }
-})().then($DONE, $DONE);
+});
diff --git a/test/harness/asyncHelpers-throwsAsync-primitive.js b/test/harness/asyncHelpers-throwsAsync-primitive.js
index a54004e2fb..fe657d0cc9 100644
--- a/test/harness/asyncHelpers-throwsAsync-primitive.js
+++ b/test/harness/asyncHelpers-throwsAsync-primitive.js
@@ -7,7 +7,7 @@ flags: [async]
 includes: [asyncHelpers.js]
 ---*/
 
-(async function () {
+asyncTest(async function () {
   var caught = false;
 
   const p = assert.throwsAsync(Error, async function () {
@@ -31,4 +31,4 @@ includes: [asyncHelpers.js]
       "assert.throwsAsync did not reject when a primitive was thrown"
     );
   }
-})().then($DONE, $DONE);
+});
diff --git a/test/harness/asyncHelpers-throwsAsync-resolved-error.js b/test/harness/asyncHelpers-throwsAsync-resolved-error.js
index 94d8a3b065..d5ad3e7947 100644
--- a/test/harness/asyncHelpers-throwsAsync-resolved-error.js
+++ b/test/harness/asyncHelpers-throwsAsync-resolved-error.js
@@ -7,7 +7,7 @@ flags: [async]
 includes: [asyncHelpers.js]
 ---*/
 
-(async function () {
+asyncTest(async function () {
   var caught = false;
 
   const p = assert.throwsAsync(
@@ -32,4 +32,4 @@ includes: [asyncHelpers.js]
       "assert.throwsAsync did not reject when the thenable resolved with an error"
     );
   }
-})().then($DONE, $DONE);
+});
diff --git a/test/harness/asyncHelpers-throwsAsync-same-realm.js b/test/harness/asyncHelpers-throwsAsync-same-realm.js
index aa5ce1743e..5e3b2b171a 100644
--- a/test/harness/asyncHelpers-throwsAsync-same-realm.js
+++ b/test/harness/asyncHelpers-throwsAsync-same-realm.js
@@ -3,12 +3,12 @@
 /*---
 description: |
     Thenables that reject with instances of the realm specified constructor function
-    satisfy the assertion, without cross realms collisions.
+    do not satisfy the assertion with cross realms collisions.
 flags: [async]
 includes: [asyncHelpers.js]
 ---*/
 
-(async function () {
+asyncTest(async function () {
   var intrinsicTypeError = TypeError;
   var caught = false;
   var realmGlobal = $262.createRealm().global;
@@ -34,4 +34,4 @@ includes: [asyncHelpers.js]
       "assert.throwsAsync did not reject when a different realm's error was thrown"
     );
   }
-})().then($DONE, $DONE);
+});
diff --git a/test/harness/asyncHelpers-throwsAsync-single-arg.js b/test/harness/asyncHelpers-throwsAsync-single-arg.js
index 196558c5a1..472d09085c 100644
--- a/test/harness/asyncHelpers-throwsAsync-single-arg.js
+++ b/test/harness/asyncHelpers-throwsAsync-single-arg.js
@@ -7,7 +7,7 @@ flags: [async]
 includes: [asyncHelpers.js]
 ---*/
 
-(async function () {
+asyncTest(async function () {
   var caught = false;
   const p = assert.throwsAsync(function () {});
   assert(p instanceof Promise);
@@ -28,4 +28,4 @@ includes: [asyncHelpers.js]
       "assert.throwsAsync did not reject when invoked with a single argumemnt"
     );
   }
-})().then($DONE, $DONE);
+});