fix(expect-util): fix comparison of DataView (#14408)

CHANGELOG.md

@@ -13,6 +13,7 @@
 ### Fixes
 
 - `[babel-plugin-jest-hoist]` Use `denylist` instead of the deprecated `blacklist` for Babel 8 support ([#14109](https://github.com/jestjs/jest/pull/14109))
+- `[@jest/expect-utils]` Fix comparison of `DataView` ([#14408](https://github.com/jestjs/jest/pull/14408))
 - `[jest-leak-detector]` Make leak-detector more aggressive when running GC ([#14526](https://github.com/jestjs/jest/pull/14526))
 - `[pretty-format]` [**BREAKING**] Print `ArrayBuffer` and `DataView` correctly ([#14290](https://github.com/facebook/jest/pull/14290))
 

packages/expect-utils/src/__tests__/utils.test.ts

@@ -571,4 +571,16 @@ describe('arrayBufferEquality', () => {
     const b = Uint8Array.from([1, 2]).buffer;
     expect(arrayBufferEquality(a, b)).toBeTruthy();
   });
+
+  test('returns true when given matching DataView', () => {
+    const a = new DataView(Uint8Array.from([1, 2, 3]).buffer);
+    const b = new DataView(Uint8Array.from([1, 2, 3]).buffer);
+    expect(arrayBufferEquality(a, b)).toBeTruthy();
+  });
+
+  test('returns false when given matching DataView', () => {
+    const a = new DataView(Uint8Array.from([1, 2, 3]).buffer);
+    const b = new DataView(Uint8Array.from([3, 2, 1]).buffer);
+    expect(arrayBufferEquality(a, b)).toBeFalsy();
+  });
 });

packages/expect-utils/src/utils.ts

@@ -390,12 +390,17 @@ export const arrayBufferEquality = (
   a: unknown,
   b: unknown,
 ): boolean | undefined => {
-  if (!(a instanceof ArrayBuffer) || !(b instanceof ArrayBuffer)) {
-    return undefined;
+  let dataViewA = a;
+  let dataViewB = b;
+
+  if (a instanceof ArrayBuffer && b instanceof ArrayBuffer) {
+    dataViewA = new DataView(a);
+    dataViewB = new DataView(b);
   }
 
-  const dataViewA = new DataView(a);
-  const dataViewB = new DataView(b);
+  if (!(dataViewA instanceof DataView && dataViewB instanceof DataView)) {
+    return undefined;
+  }
 
   // Buffers are not equal when they do not have the same byte length
   if (dataViewA.byteLength !== dataViewB.byteLength) {