Check constructor equality in .toStrictEqual()

CHANGELOG.md

@@ -5,6 +5,7 @@
 - `[pretty-format]` Option to not escape strings in diff messages ([#5661](https://github.com/facebook/jest/pull/5661))
 - `[jest-haste-map]` Add `getFileIterator` to `HasteFS` for faster file iteration ([#7010](https://github.com/facebook/jest/pull/7010)).
 - `[jest-worker]` [**BREAKING**] Add functionality to call a `setup` method in the worker before the first call and a `teardown` method when ending the farm ([#7014](https://github.com/facebook/jest/pull/7014)).
+- `[expect]` Check constructor equality in .toStrictEqual() ([#7005](https://github.com/facebook/jest/pull/7005))
 
 ### Fixes
 

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

@@ -205,13 +205,32 @@ describe('.toBe()', () => {
 });
 
 describe('.toStrictEqual()', () => {
-  class TestClass {
+  class TestClassA {
     constructor(a, b) {
       this.a = a;
       this.b = b;
     }
   }
 
+  class TestClassB {
+    constructor(a, b) {
+      this.a = a;
+      this.b = b;
+    }
+  }
+
+  const TestClassC = class Child extends TestClassA {
+    constructor(a, b) {
+      super(a, b);
+    }
+  };
+
+  const TestClassD = class Child extends TestClassB {
+    constructor(a, b) {
+      super(a, b);
+    }
+  };
+
   it('does not ignore keys with undefined values', () => {
     expect({
       a: undefined,
@@ -221,14 +240,20 @@ describe('.toStrictEqual()', () => {
 
   it('passes when comparing same type', () => {
     expect({
-      test: new TestClass(1, 2),
-    }).toStrictEqual({test: new TestClass(1, 2)});
+      test: new TestClassA(1, 2),
+    }).toStrictEqual({test: new TestClassA(1, 2)});
   });
 
   it('does not pass for different types', () => {
     expect({
-      test: new TestClass(1, 2),
-    }).not.toStrictEqual({test: {a: 1, b: 2}});
+      test: new TestClassA(1, 2),
+    }).not.toStrictEqual({test: new TestClassB(1, 2)});
+  });
+
+  it('does not simply compare constructor names', () => {
+    expect({
+      test: new TestClassC(1, 2),
+    }).not.toStrictEqual({test: new TestClassD(1, 2)});
   });
 });
 

packages/expect/src/utils.js

@@ -213,7 +213,7 @@ export const subsetEquality = (object: Object, subset: Object) => {
 };
 
 export const typeEquality = (a: any, b: any) => {
-  if (a == null || b == null || a.constructor.name === b.constructor.name) {
+  if (a == null || b == null || a.constructor === b.constructor) {
     return undefined;
   }