diff --git a/test/intl402/DurationFormat/prototype/format/taint-temporal-duration-prototype.js b/test/intl402/DurationFormat/prototype/format/taint-temporal-duration-prototype.js
new file mode 100644
index 0000000000..b6169cf1c8
--- /dev/null
+++ b/test/intl402/DurationFormat/prototype/format/taint-temporal-duration-prototype.js
@@ -0,0 +1,49 @@
+// Copyright 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.prototype.format
+description: >
+  Ensure Temporal.Duration.prototype getters aren't called.
+features: [Temporal, Intl.DurationFormat]
+---*/
+
+var duration = new Temporal.Duration(
+  1, 2, 3, 4, 5, 6, 7, 8, 9, 10
+);
+
+var formatter = new Intl.DurationFormat();
+
+var expected = formatter.format(duration);
+
+// Taint all Temporal.Duration.prototype getters.
+for (var prop of [
+  "years",
+  "months",
+  "weeks",
+  "days",
+  "hours",
+  "minutes",
+  "seconds",
+  "milliseconds",
+  "microseconds",
+  "nanoseconds",
+]) {
+  // Ensure the property is present.
+  var desc = Object.getOwnPropertyDescriptor(Temporal.Duration.prototype, prop);
+  assert.notSameValue(
+    desc,
+    undefined,
+    "Descriptor not found: " + prop
+  );
+
+  Object.defineProperty(Temporal.Duration.prototype, prop, {
+    get() {
+      throw new Test262Error();
+    }
+  });
+}
+
+var actual = formatter.format(duration);
+
+assert.sameValue(actual, expected);
diff --git a/test/intl402/DurationFormat/prototype/format/temporal-duration-object-arg.js b/test/intl402/DurationFormat/prototype/format/temporal-duration-object-arg.js
new file mode 100644
index 0000000000..f2119c156e
--- /dev/null
+++ b/test/intl402/DurationFormat/prototype/format/temporal-duration-object-arg.js
@@ -0,0 +1,41 @@
+// Copyright 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.prototype.format
+description: >
+  Temporal.Duration objects can be passed to format.
+features: [Temporal, Intl.DurationFormat]
+---*/
+
+var durations = [
+  {
+    object: new Temporal.Duration(),
+    durationLike: {
+      years: 0,
+    },
+  },
+  {
+    object: new Temporal.Duration(1, 2, 3, 4, 5, 6, 7, 8, 9, 10),
+    durationLike: {
+      years: 1,
+      months: 2,
+      weeks: 3,
+      days: 4,
+      hours: 5,
+      minutes: 6,
+      seconds: 7,
+      milliseconds: 8,
+      microseconds: 9,
+      nanoseconds: 10,
+    },
+  },
+];
+
+var formatter = new Intl.DurationFormat();
+
+for (var {object, durationLike} of durations) {
+  var expected = formatter.format(durationLike);
+  var actual = formatter.format(object);
+  assert.sameValue(actual, expected, `"${object}"`);
+}
diff --git a/test/intl402/DurationFormat/prototype/format/temporal-duration-string-arg.js b/test/intl402/DurationFormat/prototype/format/temporal-duration-string-arg.js
new file mode 100644
index 0000000000..49134d1dfd
--- /dev/null
+++ b/test/intl402/DurationFormat/prototype/format/temporal-duration-string-arg.js
@@ -0,0 +1,41 @@
+// Copyright 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.prototype.format
+description: >
+  Temporal duration strings can be passed to format.
+features: [Temporal, Intl.DurationFormat]
+---*/
+
+var durations = [
+  {
+    string: "PT0S",
+    durationLike: {
+      years: 0,
+    },
+  },
+  {
+    string: "P1Y2M3W4DT5H6M7.00800901S",
+    durationLike: {
+      years: 1,
+      months: 2,
+      weeks: 3,
+      days: 4,
+      hours: 5,
+      minutes: 6,
+      seconds: 7,
+      milliseconds: 8,
+      microseconds: 9,
+      nanoseconds: 10,
+    },
+  },
+];
+
+var formatter = new Intl.DurationFormat();
+
+for (var {string, durationLike} of durations) {
+  var expected = formatter.format(durationLike);
+  var actual = formatter.format(string);
+  assert.sameValue(actual, expected, `"${string}"`);
+}
diff --git a/test/intl402/DurationFormat/prototype/formatToParts/taint-temporal-duration-prototype.js b/test/intl402/DurationFormat/prototype/formatToParts/taint-temporal-duration-prototype.js
new file mode 100644
index 0000000000..89f745a3f5
--- /dev/null
+++ b/test/intl402/DurationFormat/prototype/formatToParts/taint-temporal-duration-prototype.js
@@ -0,0 +1,59 @@
+// Copyright 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.prototype.formatToParts
+description: >
+  Ensure Temporal.Duration.prototype getters aren't called.
+features: [Temporal, Intl.DurationFormat]
+---*/
+
+function assertSameParts(actual, expected) {
+  assert.sameValue(actual.length, expected.length);
+
+  for (var i = 0; i < actual.length; ++i) {
+    assert.sameValue(actual[i].type, expected[i].type);
+    assert.sameValue(actual[i].value, expected[i].value);
+    assert.sameValue(actual[i].unit, expected[i].unit);
+  }
+}
+
+var duration = new Temporal.Duration(
+  1, 2, 3, 4, 5, 6, 7, 8, 9, 10
+);
+
+var formatter = new Intl.DurationFormat();
+
+var expected = formatter.formatToParts(duration);
+
+// Taint all Temporal.Duration.prototype getters.
+for (var prop of [
+  "years",
+  "months",
+  "weeks",
+  "days",
+  "hours",
+  "minutes",
+  "seconds",
+  "milliseconds",
+  "microseconds",
+  "nanoseconds",
+]) {
+  // Ensure the property is present.
+  var desc = Object.getOwnPropertyDescriptor(Temporal.Duration.prototype, prop);
+  assert.notSameValue(
+    desc,
+    undefined,
+    "Descriptor not found: " + prop
+  );
+
+  Object.defineProperty(Temporal.Duration.prototype, prop, {
+    get() {
+      throw new Test262Error();
+    }
+  });
+}
+
+var actual = formatter.formatToParts(duration);
+
+assertSameParts(actual, expected);
diff --git a/test/intl402/DurationFormat/prototype/formatToParts/temporal-duration-object-arg.js b/test/intl402/DurationFormat/prototype/formatToParts/temporal-duration-object-arg.js
new file mode 100644
index 0000000000..86522119de
--- /dev/null
+++ b/test/intl402/DurationFormat/prototype/formatToParts/temporal-duration-object-arg.js
@@ -0,0 +1,51 @@
+// Copyright 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.prototype.formatToParts
+description: >
+  Temporal.Duration objects can be passed to formatToParts.
+features: [Temporal, Intl.DurationFormat]
+---*/
+
+function assertSameParts(actual, expected) {
+  assert.sameValue(actual.length, expected.length);
+
+  for (var i = 0; i < actual.length; ++i) {
+    assert.sameValue(actual[i].type, expected[i].type);
+    assert.sameValue(actual[i].value, expected[i].value);
+    assert.sameValue(actual[i].unit, expected[i].unit);
+  }
+}
+
+var durations = [
+  {
+    object: new Temporal.Duration(),
+    durationLike: {
+      years: 0,
+    },
+  },
+  {
+    object: new Temporal.Duration(1, 2, 3, 4, 5, 6, 7, 8, 9, 10),
+    durationLike: {
+      years: 1,
+      months: 2,
+      weeks: 3,
+      days: 4,
+      hours: 5,
+      minutes: 6,
+      seconds: 7,
+      milliseconds: 8,
+      microseconds: 9,
+      nanoseconds: 10,
+    },
+  },
+];
+
+var formatter = new Intl.DurationFormat();
+
+for (var {object, durationLike} of durations) {
+  var expected = formatter.format(durationLike);
+  var actual = formatter.format(object);
+  assertSameParts(actual, expected);
+}
diff --git a/test/intl402/DurationFormat/prototype/formatToParts/temporal-duration-string-arg.js b/test/intl402/DurationFormat/prototype/formatToParts/temporal-duration-string-arg.js
new file mode 100644
index 0000000000..5434ff419a
--- /dev/null
+++ b/test/intl402/DurationFormat/prototype/formatToParts/temporal-duration-string-arg.js
@@ -0,0 +1,51 @@
+// Copyright 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.prototype.formatToParts
+description: >
+  Temporal duration strings can be passed to formatToParts.
+features: [Temporal, Intl.DurationFormat]
+---*/
+
+function assertSameParts(actual, expected) {
+  assert.sameValue(actual.length, expected.length);
+
+  for (var i = 0; i < actual.length; ++i) {
+    assert.sameValue(actual[i].type, expected[i].type);
+    assert.sameValue(actual[i].value, expected[i].value);
+    assert.sameValue(actual[i].unit, expected[i].unit);
+  }
+}
+
+var durations = [
+  {
+    string: "PT0S",
+    durationLike: {
+      years: 0,
+    },
+  },
+  {
+    string: "P1Y2M3W4DT5H6M7.00800901S",
+    durationLike: {
+      years: 1,
+      months: 2,
+      weeks: 3,
+      days: 4,
+      hours: 5,
+      minutes: 6,
+      seconds: 7,
+      milliseconds: 8,
+      microseconds: 9,
+      nanoseconds: 10,
+    },
+  },
+];
+
+var formatter = new Intl.DurationFormat();
+
+for (var {string, durationLike} of durations) {
+  var expected = formatter.format(durationLike);
+  var actual = formatter.format(string);
+  assertSameParts(actual, expected);
+}
diff --git a/test/intl402/Temporal/Duration/prototype/toLocaleString/returns-same-results-as-DurationFormat.js b/test/intl402/Temporal/Duration/prototype/toLocaleString/returns-same-results-as-DurationFormat.js
new file mode 100644
index 0000000000..388bb5c5df
--- /dev/null
+++ b/test/intl402/Temporal/Duration/prototype/toLocaleString/returns-same-results-as-DurationFormat.js
@@ -0,0 +1,50 @@
+// Copyright 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.tolocalestring
+description: >
+  Tests that Temporal.Duration.prototype.toLocaleString produces the same
+  results as Intl.DurationFormat.
+features: [Temporal, Intl.DurationFormat]
+---*/
+
+var durationLike = {
+  years: 1,
+  months: 2,
+  weeks: 3,
+  days: 4,
+  hours: 5,
+  minutes: 6,
+  seconds: 7,
+  milliseconds: 8,
+  microseconds: 9,
+  nanoseconds: 10,
+};
+
+var duration = Temporal.Duration.from(durationLike);
+
+var locales = [
+  undefined,
+  "en",
+  "de",
+  "th-u-nu-thai",
+  ["ar-u-nu-arab"],
+];
+
+var options = [
+  undefined,
+  {style: "long"},
+];
+
+for (var locale of locales) {
+  for (var opts of options) {
+    var formatter = new Intl.DurationFormat(locale, opts);
+
+    assert.sameValue(
+      duration.toLocaleString(locale, opts),
+      formatter.format(durationLike),
+      `locale="${locale}", options="${JSON.stringify(opts)}", duration="${JSON.stringify(duration)}"`
+    );
+  }
+}
diff --git a/test/intl402/Temporal/Duration/prototype/toLocaleString/taint-duration-prototype.js b/test/intl402/Temporal/Duration/prototype/toLocaleString/taint-duration-prototype.js
new file mode 100644
index 0000000000..cc65f5bf2c
--- /dev/null
+++ b/test/intl402/Temporal/Duration/prototype/toLocaleString/taint-duration-prototype.js
@@ -0,0 +1,47 @@
+// Copyright 2025 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.tolocalestring
+description: >
+  Ensure Temporal.Duration.prototype getters aren't called.
+features: [Temporal, Intl.DurationFormat]
+---*/
+
+var duration = new Temporal.Duration(
+  1, 2, 3, 4, 5, 6, 7, 8, 9, 10
+);
+
+var expected = duration.toLocaleString();
+
+// Taint all Temporal.Duration.prototype getters.
+for (var prop of [
+  "years",
+  "months",
+  "weeks",
+  "days",
+  "hours",
+  "minutes",
+  "seconds",
+  "milliseconds",
+  "microseconds",
+  "nanoseconds",
+]) {
+  // Ensure the property is present.
+  var desc = Object.getOwnPropertyDescriptor(Temporal.Duration.prototype, prop);
+  assert.notSameValue(
+    desc,
+    undefined,
+    "Descriptor not found: " + prop
+  );
+
+  Object.defineProperty(Temporal.Duration.prototype, prop, {
+    get() {
+      throw new Test262Error();
+    }
+  });
+}
+
+var actual = duration.toLocaleString();
+
+assert.sameValue(actual, expected);