diff --git a/testing/asserts.ts b/testing/asserts.ts
index 19be68763e4c..b44b20a94049 100644
--- a/testing/asserts.ts
+++ b/testing/asserts.ts
@@ -52,7 +52,9 @@ function buildMessage(diffResult: ReadonlyArray<DiffResult<string>>): string[] {
   messages.push("");
   messages.push("");
   messages.push(
-    `    ${gray(bold("[Diff]"))} ${red(bold("Left"))} / ${green(bold("Right"))}`
+    `    ${gray(bold("[Diff]"))} ${red(bold("Actual"))} / ${green(
+      bold("Expected")
+    )}`
   );
   messages.push("");
   messages.push("");
diff --git a/testing/asserts_test.ts b/testing/asserts_test.ts
index 62e199298240..ac0676ed55b1 100644
--- a/testing/asserts_test.ts
+++ b/testing/asserts_test.ts
@@ -251,7 +251,9 @@ test(function testingAssertFailWithWrongErrorClass(): void {
 const createHeader = (): string[] => [
   "",
   "",
-  `    ${gray(bold("[Diff]"))} ${red(bold("Left"))} / ${green(bold("Right"))}`,
+  `    ${gray(bold("[Diff]"))} ${red(bold("Actual"))} / ${green(
+    bold("Expected")
+  )}`,
   "",
   "",
 ];