diff --git a/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-string-invalid.js b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-string-invalid.js
new file mode 100644
index 0000000000..489eba1d68
--- /dev/null
+++ b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-string-invalid.js
@@ -0,0 +1,15 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainmonthday.prototype.equals
+description: An invalid ISO string is never supported
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainMonthDay(11, 18);
+
+for (const arg of TemporalHelpers.ISO.plainMonthDayStringsInvalid()) {
+  assert.throws(RangeError, () => instance.equals(arg), `"${arg}" is not a valid PlainMonthDay string`);
+}
diff --git a/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-string.js b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-string.js
new file mode 100644
index 0000000000..f56b14cf93
--- /dev/null
+++ b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-string.js
@@ -0,0 +1,15 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainmonthday.prototype.equals
+description: A string argument is parsed into a PlainMonthDay
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainMonthDay(10, 1);
+for (const arg of TemporalHelpers.ISO.plainMonthDayStringsValid()) {
+  const result = instance.equals(arg);
+  assert.sameValue(result, true, `"${arg}" is a valid PlainMonthDay string`);
+}
diff --git a/test/built-ins/Temporal/PlainYearMonth/compare/argument-string-invalid.js b/test/built-ins/Temporal/PlainYearMonth/compare/argument-string-invalid.js
new file mode 100644
index 0000000000..57e79cbf57
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/compare/argument-string-invalid.js
@@ -0,0 +1,15 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.compare
+description: An invalid ISO string is never supported
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const arg2 = new Temporal.PlainYearMonth(1976, 11);
+for (const arg of TemporalHelpers.ISO.plainYearMonthStringsInvalid()) {
+  assert.throws(RangeError, () => Temporal.PlainYearMonth.compare(arg, arg2), `"${arg}" is invalid (first argument)`);
+  assert.throws(RangeError, () => Temporal.PlainYearMonth.compare(arg2, arg), `"${arg}" is invalid (second argument)`);
+}
diff --git a/test/built-ins/Temporal/PlainYearMonth/compare/argument-string.js b/test/built-ins/Temporal/PlainYearMonth/compare/argument-string.js
new file mode 100644
index 0000000000..e986932880
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/compare/argument-string.js
@@ -0,0 +1,19 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.compare
+description: A string is parsed into the correct object when passed as the argument
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const validStrings = TemporalHelpers.ISO.plainYearMonthStringsValid().concat(TemporalHelpers.ISO.plainYearMonthStringsValidNegativeYear());
+
+for (const arg of validStrings) {
+  assert.sameValue(
+    Temporal.PlainYearMonth.compare(arg, arg),
+    0,
+    `"${arg}" is a valid PlainYearMonth string`
+  );
+}
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-string-invalid.js b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-string-invalid.js
new file mode 100644
index 0000000000..4ccc23cbff
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-string-invalid.js
@@ -0,0 +1,15 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.equals
+description: An invalid ISO string is never supported
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(1976, 11);
+
+for (const arg of TemporalHelpers.ISO.plainYearMonthStringsInvalid()) {
+  assert.throws(RangeError, () => instance.equals(arg), `"${arg}" is not a valid PlainYearMonth string`);
+}
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-string.js b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-string.js
new file mode 100644
index 0000000000..1980803895
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-string.js
@@ -0,0 +1,21 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.equals
+description: A string argument is parsed into a PlainYearMonth
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(1976, 11);
+for (const arg of TemporalHelpers.ISO.plainYearMonthStringsValid()) {
+  const result = instance.equals(arg);
+  assert.sameValue(result, true, `"${arg}" is a valid PlainYearMonth string`);
+}
+
+const instanceNegativeYear = new Temporal.PlainYearMonth(-9999, 11);
+for (const arg of TemporalHelpers.ISO.plainYearMonthStringsValidNegativeYear()) {
+  const result = instanceNegativeYear.equals(arg);
+  assert.sameValue(result, true, `"${arg}" is a valid PlainYearMonth string`);
+}
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-string-invalid.js b/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-string-invalid.js
new file mode 100644
index 0000000000..6a66608ba9
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-string-invalid.js
@@ -0,0 +1,15 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.since
+description: An invalid ISO string is never supported
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(1976, 11);
+
+for (const arg of TemporalHelpers.ISO.plainYearMonthStringsInvalid()) {
+  assert.throws(RangeError, () => instance.since(arg), `"${arg}" is not a valid PlainYearMonth string`);
+}
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-string.js b/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-string.js
new file mode 100644
index 0000000000..48735abd8e
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-string.js
@@ -0,0 +1,21 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.since
+description: A string argument is parsed into a PlainYearMonth
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(1976, 11);
+for (const arg of TemporalHelpers.ISO.plainYearMonthStringsValid()) {
+  const result = instance.since(arg);
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, `"${arg}" is a valid PlainYearMonth string`);
+}
+
+const instanceNegativeYear = new Temporal.PlainYearMonth(-9999, 11);
+for (const arg of TemporalHelpers.ISO.plainYearMonthStringsValidNegativeYear()) {
+  const result = instanceNegativeYear.since(arg);
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, `"${arg}" is a valid PlainYearMonth string`);
+}
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-string-invalid.js b/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-string-invalid.js
new file mode 100644
index 0000000000..b7707dd823
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-string-invalid.js
@@ -0,0 +1,15 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.until
+description: An invalid ISO string is never supported
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(1976, 11);
+
+for (const arg of TemporalHelpers.ISO.plainYearMonthStringsInvalid()) {
+  assert.throws(RangeError, () => instance.until(arg), `"${arg}" is not a valid PlainYearMonth string`);
+}
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-string.js b/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-string.js
new file mode 100644
index 0000000000..161ad1e030
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-string.js
@@ -0,0 +1,21 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.until
+description: A string argument is parsed into a PlainYearMonth
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(1976, 11);
+for (const arg of TemporalHelpers.ISO.plainYearMonthStringsValid()) {
+  const result = instance.until(arg);
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, `"${arg}" is a valid PlainYearMonth string`);
+}
+
+const instanceNegativeYear = new Temporal.PlainYearMonth(-9999, 11);
+for (const arg of TemporalHelpers.ISO.plainYearMonthStringsValidNegativeYear()) {
+  const result = instanceNegativeYear.until(arg);
+  TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, `"${arg}" is a valid PlainYearMonth string`);
+}