diff --git a/test/built-ins/Temporal/Duration/prototype/add/argument-string.js b/test/built-ins/Temporal/Duration/prototype/add/argument-string.js
new file mode 100644
index 0000000000..6e129e842e
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/add/argument-string.js
@@ -0,0 +1,14 @@
+// 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.duration.prototype.add
+description: String arguments are supported.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const duration = Temporal.Duration.from({ days: 1, minutes: 5 });
+const result = duration.add("P2DT5M");
+TemporalHelpers.assertDuration(result, 0, 0, 0, 3, 0, 10, 0, 0, 0, 0, "String argument should be supported");
+assert.throws(RangeError, () => duration.add("2DT5M"), "Invalid string argument should throw");
diff --git a/test/built-ins/Temporal/Duration/prototype/add/basic.js b/test/built-ins/Temporal/Duration/prototype/add/basic.js
index 46eb1fb6cf..bcbea9aa42 100644
--- a/test/built-ins/Temporal/Duration/prototype/add/basic.js
+++ b/test/built-ins/Temporal/Duration/prototype/add/basic.js
@@ -26,3 +26,6 @@ TemporalHelpers.assertDuration(duration3.add({ minutes: 122 }),
 const duration4 = Temporal.Duration.from({ hours: -1, seconds: -3721 });
 TemporalHelpers.assertDuration(duration4.add({ minutes: 61, nanoseconds: 3722000000001 }),
   0, 0, 0, 0, 0, 1, 1, 0, 0, 1, "balancing flipped sign 2");
+TemporalHelpers.assertDuration(duration1.add({ month: 1, days: 1 }),
+  0, 0, 0, 2, 0, 5, 0, 0, 0, 0,
+  "incorrectly-spelled properties are ignored");
diff --git a/test/built-ins/Temporal/Duration/prototype/add/relativeto-month.js b/test/built-ins/Temporal/Duration/prototype/add/relativeto-month.js
new file mode 100644
index 0000000000..5523adcf70
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/add/relativeto-month.js
@@ -0,0 +1,18 @@
+// 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.duration.prototype.add
+description: relativeTo with months.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const oneMonth = new Temporal.Duration(0, 1);
+const days30 = new Temporal.Duration(0, 0, 0, 30);
+TemporalHelpers.assertDuration(oneMonth.add(days30, { relativeTo: Temporal.PlainDate.from('2018-01-01') }),
+  0, 2, 0, 2, 0, 0, 0, 0, 0, 0, "January");
+TemporalHelpers.assertDuration(oneMonth.add(days30, { relativeTo: Temporal.PlainDate.from('2018-02-01') }),
+  0, 1, 0, 30, 0, 0, 0, 0, 0, 0, "February");
+TemporalHelpers.assertDuration(oneMonth.add(days30, { relativeTo: Temporal.PlainDate.from('2018-03-01') }),
+  0, 2, 0, 0, 0, 0, 0, 0, 0, 0, "March");
diff --git a/test/built-ins/Temporal/Duration/prototype/add/relativeto-order.js b/test/built-ins/Temporal/Duration/prototype/add/relativeto-order.js
new file mode 100644
index 0000000000..3a00bd00e9
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/add/relativeto-order.js
@@ -0,0 +1,16 @@
+// 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.duration.prototype.add
+description: relativeTo with years.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const d1 = new Temporal.Duration(0, 1, 0, 0);
+const d2 = new Temporal.Duration(0, 0, 0, 30);
+const relativeTo = new Temporal.PlainDate(2000, 1, 1);
+TemporalHelpers.assertDuration(d1.add(d2, { relativeTo }),
+  0, 2, 0, 1, 0, 0, 0, 0, 0, 0,
+  "first this is resolved against relativeTo, then the argument against relativeTo + this");
diff --git a/test/built-ins/Temporal/Duration/prototype/add/relativeto-year.js b/test/built-ins/Temporal/Duration/prototype/add/relativeto-year.js
new file mode 100644
index 0000000000..1c59f3dff7
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/add/relativeto-year.js
@@ -0,0 +1,16 @@
+// 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.duration.prototype.add
+description: relativeTo with years.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const oneYear = new Temporal.Duration(1);
+const days365 = new Temporal.Duration(0, 0, 0, 365);
+TemporalHelpers.assertDuration(oneYear.add(days365, { relativeTo: Temporal.PlainDate.from("2016-01-01") }),
+  2, 0, 0, 0, 0, 0, 0, 0, 0, 0, "non-leap year");
+TemporalHelpers.assertDuration(oneYear.add(days365, { relativeTo: Temporal.PlainDate.from("2015-01-01") }),
+  1, 11, 0, 30, 0, 0, 0, 0, 0, 0, "leap year");
diff --git a/test/built-ins/Temporal/Duration/prototype/subtract/argument-string.js b/test/built-ins/Temporal/Duration/prototype/subtract/argument-string.js
new file mode 100644
index 0000000000..1cfa7b4a65
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/subtract/argument-string.js
@@ -0,0 +1,14 @@
+// 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.duration.prototype.subtract
+description: String arguments are supported.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const duration = Temporal.Duration.from({ days: 3, hours: 1, minutes: 10 });
+const result = duration.subtract('P1DT5M');
+TemporalHelpers.assertDuration(result, 0, 0, 0, 2, 1, 5, 0, 0, 0, 0, "String argument should be supported");
+assert.throws(RangeError, () => duration.subtract("2DT5M"), "Invalid string argument should throw");
diff --git a/test/built-ins/Temporal/Duration/prototype/subtract/basic.js b/test/built-ins/Temporal/Duration/prototype/subtract/basic.js
index fd221c5402..e63c53b1c9 100644
--- a/test/built-ins/Temporal/Duration/prototype/subtract/basic.js
+++ b/test/built-ins/Temporal/Duration/prototype/subtract/basic.js
@@ -61,3 +61,6 @@ TemporalHelpers.assertDuration(d1.subtract({ minutes: 122 }),
 const d2 = Temporal.Duration.from({ hours: 1, seconds: 3721 });
 TemporalHelpers.assertDuration(d2.subtract({ minutes: 61, nanoseconds: 3722000000001 }),
   0, 0, 0, 0, 0, -1, -1, 0, 0, -1);
+TemporalHelpers.assertDuration(duration.subtract({ month: 1, days: 1 }),
+  0, 0, 0, 2, 1, 10, 0, 0, 0, 0,
+  "incorrectly-spelled properties are ignored");
diff --git a/test/built-ins/Temporal/Duration/prototype/subtract/relativeto-month.js b/test/built-ins/Temporal/Duration/prototype/subtract/relativeto-month.js
new file mode 100644
index 0000000000..e54edd8649
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/subtract/relativeto-month.js
@@ -0,0 +1,18 @@
+// 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.duration.prototype.subtract
+description: relativeTo with months.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const oneMonth = new Temporal.Duration(0, 1);
+const days30 = new Temporal.Duration(0, 0, 0, 30);
+TemporalHelpers.assertDuration(oneMonth.subtract(days30, { relativeTo: Temporal.PlainDate.from('2018-02-01') }),
+  0, 0, 0, -2, 0, 0, 0, 0, 0, 0, "February");
+TemporalHelpers.assertDuration(oneMonth.subtract(days30, { relativeTo: Temporal.PlainDate.from('2018-03-01') }),
+  0, 0, 0, 1, 0, 0, 0, 0, 0, 0, "March");
+TemporalHelpers.assertDuration(oneMonth.subtract(days30, { relativeTo: Temporal.PlainDate.from('2018-04-01') }),
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "April");
diff --git a/test/built-ins/Temporal/Duration/prototype/subtract/relativeto-order.js b/test/built-ins/Temporal/Duration/prototype/subtract/relativeto-order.js
new file mode 100644
index 0000000000..cbb51076bc
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/subtract/relativeto-order.js
@@ -0,0 +1,16 @@
+// 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.duration.prototype.subtract
+description: relativeTo with years.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const d1 = new Temporal.Duration(0, 2, 1, 4);
+const d2 = new Temporal.Duration(0, 1, 1, 1);
+const relativeTo = new Temporal.PlainDate(2000, 1, 1);
+TemporalHelpers.assertDuration(d1.subtract(d2, { relativeTo }),
+  0, 1, 0, 3, 0, 0, 0, 0, 0, 0,
+  "first this is resolved against relativeTo, then the argument against relativeTo + this");
diff --git a/test/built-ins/Temporal/Duration/prototype/subtract/relativeto-year.js b/test/built-ins/Temporal/Duration/prototype/subtract/relativeto-year.js
new file mode 100644
index 0000000000..86a4090f93
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/subtract/relativeto-year.js
@@ -0,0 +1,16 @@
+// 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.duration.prototype.subtract
+description: relativeTo with years.
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const oneYear = new Temporal.Duration(1);
+const days365 = new Temporal.Duration(0, 0, 0, 365);
+TemporalHelpers.assertDuration(oneYear.subtract(days365, { relativeTo: Temporal.PlainDate.from("2017-01-01") }),
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "non-leap year");
+TemporalHelpers.assertDuration(oneYear.subtract(days365, { relativeTo: Temporal.PlainDate.from("2016-01-01") }),
+  0, 0, 0, 1, 0, 0, 0, 0, 0, 0, "leap year");