[expect] Add negative equality tests (#8260)

* Add negative equality tests

* Add changelog entry

CHANGELOG.md

@@ -7,6 +7,7 @@
 
 ### Fixes
 
+- `[expect]` Add negative equality tests for iterables ([#8260](https://github.com/facebook/jest/pull/8260))
 - `[jest-haste-map]` Resolve fs watcher EMFILE error ([#8258](https://github.com/facebook/jest/pull/8258))
 
 ### Chore & Maintenance

packages/expect/src/__tests__/utils.test.js

@@ -241,6 +241,36 @@ describe('iterableEquality', () => {
     ).toBe(false);
   });
 
+  test('returns false when given inequal set within a set', () => {
+    expect(
+      iterableEquality(new Set([new Set([2])]), new Set([new Set([1, 2])])),
+    ).toBe(false);
+    expect(
+      iterableEquality(new Set([new Set([2])]), new Set([new Set([1, 2])])),
+    ).toBe(false);
+  });
+
+  test('returns false when given inequal map within a set', () => {
+    expect(
+      iterableEquality(
+        new Set([new Map([['a', 2]])]),
+        new Set([new Map([['a', 3]])]),
+      ),
+    ).toBe(false);
+    expect(
+      iterableEquality(new Set([new Set([2])]), new Set([new Set([1, 2])])),
+    ).toBe(false);
+  });
+
+  test('returns false when given inequal set within a map', () => {
+    expect(
+      iterableEquality(
+        new Map([['one', new Set([2])]]),
+        new Map([['one', new Set([1, 2])]]),
+      ),
+    ).toBe(false);
+  });
+
   test('returns true when given circular Set shape', () => {
     const a1 = new Set();
     const a2 = new Set();

packages/expect/src/utils.ts

@@ -172,7 +172,7 @@ export const iterableEquality = (
   bStack.push(b);
 
   const iterableEqualityWithStack = (a: any, b: any) =>
-    iterableEquality(a, b, aStack, bStack);
+    iterableEquality(a, b, [...aStack], [...bStack]);
 
   if (a.size !== undefined) {
     if (a.size !== b.size) {