From 6252af6539ab957b0ad4ca69465cf9514dd21316 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Olle=20Lauri=20Bostr=C3=B6m?= <ollebostr@gmail.com>
Date: Wed, 19 Sep 2018 23:19:15 +0200
Subject: [PATCH] Check constructor equality in .toStrictEqual()

---
 CHANGELOG.md                                  |  1 +
 .../expect/src/__tests__/matchers.test.js     | 36 ++++++++++++++++---
 packages/expect/src/utils.js                  |  2 +-
 3 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1020684b838e..8dbfbfad66f5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 - `[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)).
 - `[jest-config]` [**BREAKING**] Set default `notifyMode` to `failure-change` ([#7024](https://github.com/facebook/jest/pull/7024))
 - `[jest-snapshot]` Enable configurable snapshot paths ([#6143](https://github.com/facebook/jest/pull/6143))
+- `[expect]` Check constructor equality in .toStrictEqual() ([#7005](https://github.com/facebook/jest/pull/7005))
 
 ### Fixes
 
diff --git a/packages/expect/src/__tests__/matchers.test.js b/packages/expect/src/__tests__/matchers.test.js
index 36132f537bb1..e695eec418ed 100644
--- a/packages/expect/src/__tests__/matchers.test.js
+++ b/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 +240,21 @@ 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', () => {
+    const c = new TestClassC(1, 2);
+    const d = new TestClassD(1, 2);
+    expect(c.constructor.name).toEqual(d.constructor.name);
+    expect({test: c}).not.toStrictEqual({test: d});
   });
 });
 
diff --git a/packages/expect/src/utils.js b/packages/expect/src/utils.js
index c25e9cc46c5d..9a7a0220fac5 100644
--- a/packages/expect/src/utils.js
+++ b/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;
   }