diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-always.js b/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-always.js
new file mode 100644
index 0000000000..d6fa52e106
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-always.js
@@ -0,0 +1,22 @@
+// 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.protoype.tostring
+description: always value for calendarName option
+features: [Temporal]
+---*/
+
+const calendar = {
+  toString() { return "custom"; }
+};
+const yearmonth1 = new Temporal.PlainYearMonth(2000, 5);
+const yearmonth2 = new Temporal.PlainYearMonth(2000, 5, calendar);
+
+[
+  [yearmonth1, "2000-05[u-ca=iso8601]"],
+  [yearmonth2, "2000-05-01[u-ca=custom]"],
+].forEach(([yearmonth, expected]) => {
+  const result = yearmonth.toString({ calendarName: "always" });
+  assert.sameValue(result, expected, "calendarName is always");
+});
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-auto.js b/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-auto.js
new file mode 100644
index 0000000000..3aa15bac39
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-auto.js
@@ -0,0 +1,22 @@
+// 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.protoype.tostring
+description: auto value for calendarName option
+features: [Temporal]
+---*/
+
+const calendar = {
+  toString() { return "custom"; }
+};
+const yearmonth1 = new Temporal.PlainYearMonth(2000, 5);
+const yearmonth2 = new Temporal.PlainYearMonth(2000, 5, calendar);
+
+[
+  [yearmonth1, "2000-05"],
+  [yearmonth2, "2000-05-01[u-ca=custom]"],
+].forEach(([yearmonth, expected]) => {
+  const result = yearmonth.toString({ calendarName: "auto" });
+  assert.sameValue(result, expected, "calendarName is auto");
+});
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-invalid-string.js b/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-invalid-string.js
index e1b8b71025..23f0ffc9c5 100644
--- a/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-invalid-string.js
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-invalid-string.js
@@ -15,4 +15,6 @@ features: [Temporal]
 ---*/
 
 const yearmonth = new Temporal.PlainYearMonth(2000, 5);
-assert.throws(RangeError, () => yearmonth.toString({ calendarName: "other string" }));
+for (const calendarName of ["ALWAYS", "sometimes", "other string"]) {
+  assert.throws(RangeError, () => yearmonth.toString({ calendarName }));
+}
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-never.js b/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-never.js
new file mode 100644
index 0000000000..e7dd619b9f
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/toString/calendarname-never.js
@@ -0,0 +1,22 @@
+// 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.protoype.tostring
+description: never value for calendarName option
+features: [Temporal]
+---*/
+
+const calendar = {
+  toString() { return "custom"; }
+};
+const yearmonth1 = new Temporal.PlainYearMonth(2000, 5);
+const yearmonth2 = new Temporal.PlainYearMonth(2000, 5, calendar);
+
+[
+  [yearmonth1, "2000-05"],
+  [yearmonth2, "2000-05-01"],
+].forEach(([yearmonth, expected]) => {
+  const result = yearmonth.toString({ calendarName: "never" });
+  assert.sameValue(result, expected, "calendarName is never");
+});