Introduce toStrictEqual

CHANGELOG.md

@@ -71,6 +71,8 @@
   ([#5980](https://github.com/facebook/jest/pull/5980))
 * `[jest-message-util]` Include column in stack frames
   ([#5889](https://github.com/facebook/jest/pull/5889))
+* `[expect]` Introduce toStrictEqual
+  ([#6032](https://github.com/facebook/jest/pull/6032))
 
 ### Fixes
 

docs/ExpectAPI.md

@@ -1096,6 +1096,33 @@ from the test.
 _Note: While snapshot testing is most commonly used with React components, any
 serializable value can be used as a snapshot._
 
+### `.toStrictEqual(value)`
+
+Use `.toStrictEqual` to test that objects have the same types as well as
+structure.
+
+Differences from `.toEqual`:
+
+* Keys with `undefined` properties are checked. e.g. `{a: undefined, b: 2}` does
+  not match `{b: 2}` when using `.toStrictEqual`.
+* Object types are checked to be equal. e.g. A class instance with fields `a`
+  and `b` will not equal a literal object with fields `a` and `b`.
+
+```js
+class LaCroix {
+  constructor(flavor) {
+    this.flavor = flavor;
+  }
+}
+
+describe('the La Croix cans on my desk', () => {
+  test('are not semantically the same', () => {
+    expect(new LaCroix('lemon')).toEqual({flavor: 'lemon'});
+    expect(new LaCroix('lemon')).not.toStrictEqual({flavor: 'lemon'});
+  });
+});
+```
+
 ### `.toThrow(error)`
 
 Also under the alias: `.toThrowError(error)`

integration-tests/snapshot-escape/__tests__/__snapshots__/snapshot_escape_regex.js.snap

@@ -0,0 +1,9 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`escape regex 1`] = `/\\\\dd\\\\ \\\\s\\+ \\\\w \\\\\\\\\\\\\\[ \\\\\\. blahzz\\.\\* \\[xyz\\]\\+/`;
+
+exports[`escape regex nested in object 1`] = `
+Object {
+  "regex": /\\\\dd\\\\ \\\\s\\+ \\\\w \\\\\\\\\\\\\\[ \\\\\\. blahzz\\.\\* \\[xyz\\]\\+/,
+}
+`;

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

@@ -204,6 +204,34 @@ describe('.toBe()', () => {
   });
 });
 
+describe('.toStrictEqual()', () => {
+  class TestClass {
+    constructor(a, b) {
+      this.a = a;
+      this.b = b;
+    }
+  }
+
+  it('does not ignore keys with undefined values', () => {
+    expect({
+      a: undefined,
+      b: 2,
+    }).not.toStrictEqual({b: 2});
+  });
+
+  it('passes when comparing same type', () => {
+    expect({
+      test: new TestClass(1, 2),
+    }).toStrictEqual({test: new TestClass(1, 2)});
+  });
+
+  it('does not pass for different types', () => {
+    expect({
+      test: new TestClass(1, 2),
+    }).not.toStrictEqual({test: {a: 1, b: 2}});
+  });
+});
+
 describe('.toEqual()', () => {
   [
     [true, false],

packages/expect/src/jasmine_utils.js

@@ -28,9 +28,9 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 type Tester = (a: any, b: any) => boolean | typeof undefined;
 
 // Extracted out of jasmine 2.5.2
-export function equals(a: any, b: any, customTesters?: Array<Tester>): boolean {
+export function equals(a: any, b: any, customTesters?: Array<Tester>, strictCheck?: boolean): boolean {
   customTesters = customTesters || [];
-  return eq(a, b, [], [], customTesters);
+  return eq(a, b, [], [], customTesters, strictCheck ? hasKey : hasDefinedKey);
 }
 
 function isAsymmetric(obj) {
@@ -56,7 +56,7 @@ function asymmetricMatch(a, b) {
 
 // Equality function lovingly adapted from isEqual in
 //   [Underscore](http://underscorejs.org)
-function eq(a, b, aStack, bStack, customTesters): boolean {
+function eq(a, b, aStack, bStack, customTesters, hasKey): boolean {
   var result = true;
 
   var asymmetricResult = asymmetricMatch(a, b);
@@ -160,28 +160,28 @@ function eq(a, b, aStack, bStack, customTesters): boolean {
     }
 
     while (size--) {
-      result = eq(a[size], b[size], aStack, bStack, customTesters);
+      result = eq(a[size], b[size], aStack, bStack, customTesters, hasKey);
       if (!result) {
         return false;
       }
     }
   }
 
   // Deep compare objects.
-  var aKeys = keys(a, className == '[object Array]'),
+  var aKeys = keys(a, className == '[object Array]', hasKey),
     key;
   size = aKeys.length;
 
   // Ensure that both objects contain the same number of properties before comparing deep equality.
-  if (keys(b, className == '[object Array]').length !== size) {
+  if (keys(b, className == '[object Array]', hasKey).length !== size) {
     return false;
   }
 
   while (size--) {
     key = aKeys[size];
 
     // Deep compare each member
-    result = has(b, key) && eq(a[key], b[key], aStack, bStack, customTesters);
+    result = hasKey(b, key) && eq(a[key], b[key], aStack, bStack, customTesters, hasKey);
 
     if (!result) {
       return false;
@@ -194,11 +194,11 @@ function eq(a, b, aStack, bStack, customTesters): boolean {
   return result;
 }
 
-function keys(obj, isArray) {
+function keys(obj, isArray, hasKey) {
   var allKeys = (function(o) {
     var keys = [];
     for (var key in o) {
-      if (has(o, key)) {
+      if (hasKey(o, key)) {
         keys.push(key);
       }
     }
@@ -223,9 +223,15 @@ function keys(obj, isArray) {
   return extraKeys;
 }
 
-function has(obj, key) {
+function hasDefinedKey(obj, key) {
   return (
-    Object.prototype.hasOwnProperty.call(obj, key) && obj[key] !== undefined
+    hasKey(obj, key) && obj[key] !== undefined
+  );
+}
+
+function hasKey(obj, key) {
+  return (
+    Object.prototype.hasOwnProperty.call(obj, key)
   );
 }
 

packages/expect/src/matchers.js

@@ -29,6 +29,7 @@ import {
   getPath,
   iterableEquality,
   subsetEquality,
+  typeEquality,
 } from './utils';
 import {equals} from './jasmine_utils';
 
@@ -615,6 +616,43 @@ const matchers: MatchersObject = {
 
     return {message, pass};
   },
+
+  toStrictEqual(received: any, expected: any) {
+    const pass = equals(
+      received,
+      expected,
+      [iterableEquality, typeEquality],
+      true,
+    );
+
+    const message = pass
+      ? () =>
+          matcherHint('.not.toStrictEqual') +
+          '\n\n' +
+          `Expected value to not equal:\n` +
+          `  ${printExpected(expected)}\n` +
+          `Received:\n` +
+          `  ${printReceived(received)}`
+      : () => {
+          const diffString = diff(expected, received, {
+            expand: this.expand,
+          });
+          return (
+            matcherHint('.toStrictEqual') +
+            '\n\n' +
+            `Expected value to equal:\n` +
+            `  ${printExpected(expected)}\n` +
+            `Received:\n` +
+            `  ${printReceived(received)}` +
+            (diffString ? `\n\nDifference:\n\n${diffString}` : '')
+          );
+        };
+
+    // Passing the the actual and expected objects so that a custom reporter
+    // could access them, for example in order to display a custom visual diff,
+    // or create a different error message
+    return {actual: received, expected, message, name: 'toStrictEqual', pass};
+  },
 };
 
 export default matchers;

packages/expect/src/utils.js

@@ -185,6 +185,14 @@ 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) {
+    return undefined;
+  }
+
+  return false;
+};
+
 export const partition = <T>(
   items: Array<T>,
   predicate: T => boolean,