One spec by matcher for property based tests

packages/expect/src/__tests__/__arbitraries__/sharedSettings.ts

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+import fc from 'fast-check';
+
+// settings for anything arbitrary
+export const anythingSettings = {
+  key: fc.oneof(fc.string(), fc.constantFrom('k1', 'k2', 'k3')),
+  withBoxedValues: true,
+  // Issue #7975 have to be fixed before enabling the generation of Map
+  withMap: false,
+  // Issue #7975 have to be fixed before enabling the generation of Set
+  withSet: false,
+};
+
+// assertion settings
+export const assertSettings = {}; // eg.: {numRuns: 10000}

packages/expect/src/__tests__/matchers-toContain.property.test.ts

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+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
+import fc from 'fast-check';
+import {
+  anythingSettings,
+  assertSettings,
+} from './__arbitraries__/sharedSettings';
+
+describe('toContain', () => {
+  it('should always find the value when inside the array', () => {
+    fc.assert(
+      fc.property(
+        fc.array(fc.anything(anythingSettings)),
+        fc.array(fc.anything(anythingSettings)),
+        fc.anything(anythingSettings).filter(v => !Number.isNaN(v)),
+        (startValues, endValues, v) => {
+          // Given:  startValues, endValues arrays and v value (not NaN)
+          // Assert: We expect `expect([...startValues, v, ...endValues]).toContain(v)`
+          expect([...startValues, v, ...endValues]).toContain(v);
+        },
+      ),
+      assertSettings,
+    );
+  });
+
+  it('should not find the value if it has been cloned into the array', () => {
+    fc.assert(
+      fc.property(
+        fc.array(fc.anything(anythingSettings)),
+        fc.array(fc.anything(anythingSettings)),
+        fc.dedup(fc.anything(anythingSettings), 2),
+        (startValues, endValues, [a, b]) => {
+          // Given:  startValues, endValues arrays
+          //         and [a, b] equal, but not the same values
+          //         with `typeof a === 'object && a !== null`
+          // Assert: We expect `expect([...startValues, a, ...endValues]).not.toContain(b)`
+          fc.pre(typeof a === 'object' && a !== null);
+          expect([...startValues, a, ...endValues]).not.toContain(b);
+        },
+      ),
+      assertSettings,
+    );
+  });
+});

packages/expect/src/__tests__/matchers-toContainEqual.property.test.ts

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+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
+import fc from 'fast-check';
+import {
+  anythingSettings,
+  assertSettings,
+} from './__arbitraries__/sharedSettings';
+
+describe('toContainEqual', () => {
+  it('should always find the value when inside the array', () => {
+    fc.assert(
+      fc.property(
+        fc.array(fc.anything(anythingSettings)),
+        fc.array(fc.anything(anythingSettings)),
+        fc.anything(anythingSettings),
+        (startValues, endValues, v) => {
+          // Given:  startValues, endValues arrays and v any value
+          // Assert: We expect `expect([...startValues, v, ...endValues]).toContainEqual(v)`
+          expect([...startValues, v, ...endValues]).toContainEqual(v);
+        },
+      ),
+      assertSettings,
+    );
+  });
+
+  it('should always find the value when cloned inside the array', () => {
+    fc.assert(
+      fc.property(
+        fc.array(fc.anything(anythingSettings)),
+        fc.array(fc.anything(anythingSettings)),
+        fc.dedup(fc.anything(anythingSettings), 2),
+        (startValues, endValues, [a, b]) => {
+          // Given:  startValues, endValues arrays
+          //         and [a, b] identical values
+          // Assert: We expect `expect([...startValues, a, ...endValues]).toContainEqual(b)`
+          expect([...startValues, a, ...endValues]).toContainEqual(b);
+        },
+      ),
+      assertSettings,
+    );
+  });
+});

packages/expect/src/__tests__/matchers-toEqual.property.test.ts

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+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
+import fc from 'fast-check';
+import {
+  anythingSettings,
+  assertSettings,
+} from './__arbitraries__/sharedSettings';
+
+describe('toEqual', () => {
+  it('should be reflexive', () => {
+    fc.assert(
+      fc.property(fc.dedup(fc.anything(anythingSettings), 2), ([a, b]) => {
+        // Given:  a and b identical values
+        // Assert: We expect `expect(a).toEqual(b)`
+        expect(a).toEqual(b);
+      }),
+      assertSettings,
+    );
+  });
+
+  it('should be symmetric', () => {
+    const safeExpectEqual = (a, b) => {
+      try {
+        expect(a).toEqual(b);
+        return true;
+      } catch (err) {
+        return false;
+      }
+    };
+    fc.assert(
+      fc.property(
+        fc.anything(anythingSettings),
+        fc.anything(anythingSettings),
+        (a, b) => {
+          // Given: a and b values
+          // Assert: We expect `expect(a).toEqual(b)`
+          //         to be equivalent to `expect(b).toEqual(a)`
+          expect(safeExpectEqual(a, b)).toBe(safeExpectEqual(b, a));
+        },
+      ),
+      {
+        ...assertSettings,
+        examples: [
+          [0, 5e-324], // Issue #7941
+          // [
+          //   new Set([false, true]),
+          //   new Set([new Boolean(true), new Boolean(true)]),
+          // ], // Issue #7975
+        ],
+      },
+    );
+  });
+});

packages/expect/src/__tests__/matchers-toStrictEqual.property.test.ts

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+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
+import fc from 'fast-check';
+import {
+  anythingSettings,
+  assertSettings,
+} from './__arbitraries__/sharedSettings';
+
+describe('toStrictEqual', () => {
+  it('should be reflexive', () => {
+    fc.assert(
+      fc.property(fc.dedup(fc.anything(anythingSettings), 2), ([a, b]) => {
+        // Given:  a and b identical values
+        // Assert: We expect `expect(a).toStrictEqual(b)`
+        expect(a).toStrictEqual(b);
+      }),
+      assertSettings,
+    );
+  });
+
+  it('should be symmetric', () => {
+    const safeExpectStrictEqual = (a, b) => {
+      try {
+        expect(a).toEqual(b);
+        return true;
+      } catch (err) {
+        return false;
+      }
+    };
+    fc.assert(
+      fc.property(
+        fc.anything(anythingSettings),
+        fc.anything(anythingSettings),
+        (a, b) => {
+          // Given:  a and b values
+          // Assert: We expect `expect(a).toStrictEqual(b)`
+          //         to be equivalent to `expect(b).toStrictEqual(a)`
+          expect(safeExpectStrictEqual(a, b)).toBe(safeExpectStrictEqual(b, a));
+        },
+      ),
+      assertSettings,
+    );
+  });
+});