diff --git a/harness/temporalHelpers.js b/harness/temporalHelpers.js
index 963498b909..d34fd2deda 100644
--- a/harness/temporalHelpers.js
+++ b/harness/temporalHelpers.js
@@ -252,7 +252,7 @@ var TemporalHelpers = {
    * calendar object (so that it doesn't have to call the calendar getter itself
    * if it wants to make any assertions about the calendar.)
    */
-  checkPlainDateTimeConversionFastPath(func) {
+  checkPlainDateTimeConversionFastPath(func, message = "checkPlainDateTimeConversionFastPath") {
     const actual = [];
     const expected = [];
 
@@ -285,7 +285,7 @@ var TemporalHelpers = {
     });
 
     func(datetime, calendar);
-    assert.compareArray(actual, expected, "property getters not called");
+    assert.compareArray(actual, expected, `${message}: property getters not called`);
   },
 
   /*
diff --git a/test/built-ins/Temporal/PlainDate/compare/argument-plaindatetime.js b/test/built-ins/Temporal/PlainDate/compare/argument-plaindatetime.js
index a41d6b0b08..be83e03a68 100644
--- a/test/built-ins/Temporal/PlainDate/compare/argument-plaindatetime.js
+++ b/test/built-ins/Temporal/PlainDate/compare/argument-plaindatetime.js
@@ -15,14 +15,36 @@ includes: [compareArray.js, temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const date = new Temporal.PlainDate(2000, 5, 2);
+const sameDate = new Temporal.PlainDate(2000, 5, 2);
+const earlierDate = new Temporal.PlainDate(1920, 7, 3);
+const laterDate = new Temporal.PlainDate(2005, 1, 12);
 
 TemporalHelpers.checkPlainDateTimeConversionFastPath((datetime) => {
-  const result = Temporal.PlainDate.compare(datetime, date);
-  assert.sameValue(result, 0, "comparison result");
-});
+  const result = Temporal.PlainDate.compare(datetime, sameDate);
+  assert.sameValue(result, 0, "First argument, same date: comparison result");
+}, "First argument, same date");
 
 TemporalHelpers.checkPlainDateTimeConversionFastPath((datetime) => {
-  const result = Temporal.PlainDate.compare(date, datetime);
-  assert.sameValue(result, 0, "comparison result");
-});
+  const result = Temporal.PlainDate.compare(datetime, earlierDate);
+  assert.sameValue(result, 1, "First argument, earlier date: comparison result");
+}, "First argument, earlier date");
+
+TemporalHelpers.checkPlainDateTimeConversionFastPath((datetime) => {
+  const result = Temporal.PlainDate.compare(datetime, laterDate);
+  assert.sameValue(result, -1, "First argument, later date: comparison result");
+}, "First argument, later date");
+
+TemporalHelpers.checkPlainDateTimeConversionFastPath((datetime) => {
+  const result = Temporal.PlainDate.compare(sameDate, datetime);
+  assert.sameValue(result, 0, "Second argument, same date: comparison result");
+}, "Second argument, same date");
+
+TemporalHelpers.checkPlainDateTimeConversionFastPath((datetime) => {
+  const result = Temporal.PlainDate.compare(earlierDate, datetime);
+  assert.sameValue(result, -1, "Second argument, earlier date: comparison result");
+}, "Second argument, earlier date");
+
+TemporalHelpers.checkPlainDateTimeConversionFastPath((datetime) => {
+  const result = Temporal.PlainDate.compare(laterDate, datetime);
+  assert.sameValue(result, 1, "Second argument, later date: comparison result");
+}, "Second argument, later date");
diff --git a/test/built-ins/Temporal/PlainDate/compare/argument-zoneddatetime.js b/test/built-ins/Temporal/PlainDate/compare/argument-zoneddatetime.js
new file mode 100644
index 0000000000..1b45929bea
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/compare/argument-zoneddatetime.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.plaindate.compare
+description: ZonedDateTime is supported.
+features: [Temporal]
+---*/
+
+const zdt = new Temporal.ZonedDateTime(0n, "UTC");
+assert.sameValue(
+  Temporal.PlainDate.compare(zdt, new Temporal.PlainDate(1970, 1, 1)),
+  0, "same date, ZDT first");
+assert.sameValue(
+  Temporal.PlainDate.compare(zdt, new Temporal.PlainDate(1970, 1, 1)),
+  0, "same date, ZDT second");
+assert.sameValue(
+  Temporal.PlainDate.compare(zdt, new Temporal.PlainDate(1976, 11, 18)),
+  -1, "different date, ZDT first");
+assert.sameValue(
+  Temporal.PlainDate.compare(new Temporal.PlainDate(1976, 11, 18), zdt),
+  1, "different date, ZDT second");