diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/argument-string.js b/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/argument-string.js
new file mode 100644
index 0000000000..b75ace828f
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/argument-string.js
@@ -0,0 +1,37 @@
+// 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.plaindatetime.prototype.withcalendar
+description: String argument, if it names a recognizable calendar, gets cast
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = {
+  toString() { return "something special"; }
+};
+const dt = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, calendar);
+const result = dt.withCalendar("iso8601");
+
+TemporalHelpers.assertPlainDateTime(
+  result,
+  1976, 11, "M11", 18, 15, 23, 30, 123, 456, 789,
+  "'iso8601' is a recognizable calendar"
+);
+
+const resultCalendar = result.calendar;
+
+assert.sameValue(
+  resultCalendar instanceof Temporal.Calendar,
+  true,
+  "underlying calendar is no longer a plain object"
+);
+
+assert.sameValue(resultCalendar.toString(), "iso8601", "underlying calendar has changed");
+
+assert.throws(
+  RangeError,
+  () => dt.withCalendar("this will fail"),
+  "unknown calendar throws"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/basic.js b/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/basic.js
new file mode 100644
index 0000000000..318f552ab5
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/basic.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.plaindatetime.prototype.withcalendar
+description: Non-throwing non-edge case
+features: [Temporal]
+includes: [temporalHelpers.js]
+---*/
+
+const dt = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789);
+const calendar = new Temporal.Calendar("iso8601");
+
+const result = dt.withCalendar(calendar);
+
+TemporalHelpers.assertPlainDateTime(
+  result,
+  1976, 11, "M11", 18, 15, 23, 30, 123, 456, 789,
+  "works"
+);
+
+assert.sameValue(result.calendar, calendar, "underlying calendar is unchanged");