Add toBeFalse (#89)

* Add toBeFalse predicate

* Add toBeFalse matcher

* Update docs and add contributor

* Add toBeFalse to matchers index

.all-contributorsrc

@@ -121,6 +121,16 @@
         "test"
       ]
     },
+    {
+      "login": "mjmiles",
+      "name": "mjmiles",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/33098064?v=4",
+      "profile": "https://github.com/mjmiles",
+      "contributions": [
+        "code",
+        "doc"
+      ]
+    },
     {
       "login": "garmeeh",
       "name": "Gary Meehan",

README.md

@@ -119,8 +119,6 @@ test('is jest cool', () => {
 
 ### .toBeFalse()
 
-_Note: Currently unimplemented_
-
 Use `.toBeFalse` when checking a value is equal (===) to `false`.
 
 ```js

src/matchers/index.js

@@ -1,5 +1,6 @@
 import toBeEven from './toBeEven';
 import toBeTrue from './toBeTrue';
+import toBeFalse from './toBeFalse';
 import toContainValue from './toContainValue';
 import toContainValues from './toContainValues';
 import toEqualCaseInsensitive from './toEqualCaseInsensitive';
@@ -27,6 +28,7 @@ import toInclude from './toInclude';
 export default [
   toBeEven,
   toBeTrue,
+  toBeFalse,
   toContainValue,
   toContainValues,
   toEqualCaseInsensitive,

src/matchers/toBeFalse/__snapshots__/index.test.js.snap

@@ -0,0 +1,17 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`.not.toBeFalse fails when given false 1`] = `
+"<dim>expect(</><red>received</><dim>).not.toBeFalse(</><dim>)</>
+
+Expected value to not be false received:
+  <red>false</>"
+`;
+
+exports[`.toBeFalse fails when not given false 1`] = `
+"<dim>expect(</><red>received</><dim>).toBeFalse(</><dim>)</>
+
+Expected value to be false:
+  <green>false</>
+Received:
+  <red>true</>"
+`;

src/matchers/toBeFalse/index.js

@@ -0,0 +1,28 @@
+import { matcherHint, printExpected, printReceived } from 'jest-matcher-utils';
+
+import predicate from './predicate';
+
+const passMessage = received => () =>
+  matcherHint('.not.toBeFalse', 'received', '') +
+  '\n\n' +
+  'Expected value to not be false received:\n' +
+  `  ${printReceived(received)}`;
+
+const failMessage = received => () =>
+  matcherHint('.toBeFalse', 'received', '') +
+  '\n\n' +
+  'Expected value to be false:\n' +
+  `  ${printExpected(false)}\n` +
+  'Received:\n' +
+  `  ${printReceived(received)}`;
+
+export default {
+  toBeFalse: expected => {
+    const pass = predicate(expected);
+    if (pass) {
+      return { pass: true, message: passMessage(expected) };
+    }
+
+    return { pass: false, message: failMessage(expected) };
+  }
+};

src/matchers/toBeFalse/index.test.js

@@ -0,0 +1,28 @@
+import each from 'jest-each';
+
+import matcher from './';
+
+expect.extend(matcher);
+
+describe('.toBeFalse', () => {
+  it('passes when given false', () => {
+    expect(false).toBeFalse();
+  });
+
+  it('fails when not given false', () => {
+    expect(() => expect(true).toBeFalse()).toThrowErrorMatchingSnapshot();
+  });
+});
+
+describe('.not.toBeFalse', () => {
+  each([[true], [''], [0], [{}], [[]], [() => {}], [undefined], [null], [NaN]]).it(
+    'passes when not given false: %s',
+    given => {
+      expect(given).not.toBeFalse();
+    }
+  );
+
+  it('fails when given false', () => {
+    expect(() => expect(false).not.toBeFalse()).toThrowErrorMatchingSnapshot();
+  });
+});

src/matchers/toBeFalse/predicate.js

@@ -0,0 +1 @@
+export default expected => expected === false;

src/matchers/toBeFalse/predicate.test.js

@@ -0,0 +1,15 @@
+import each from 'jest-each';
+import predicate from './predicate';
+
+describe('toBeFalse Predicate', () => {
+  it('returns true when given false', () => {
+    expect(predicate(false)).toBe(true);
+  });
+
+  each([[true], [''], [0], [{}], [[]], [() => {}], [undefined], [null], [NaN]]).it(
+    'returns false when given: %s',
+    given => {
+      expect(predicate(given)).toBe(false);
+    }
+  );
+});