feat(rules): add consistent-test-it rule

Fixes #12

README.md

@@ -80,6 +80,7 @@ for more information about extending configuration files.
 
 | Rule                                                               | Description                                                     | Recommended                                                             | Fixable                                                     |
 | ------------------------------------------------------------------ | --------------------------------------------------------------- | ----------------------------------------------------------------------- | ----------------------------------------------------------- |
+| [consistent-test-it](docs/rules/consistent-test-it.md)             | Enforce consistent test or it keyword                           |                                                                         | ![fixable](https://img.shields.io/badge/-fixable-green.svg) |
 | [no-disabled-tests](docs/rules/no-disabled-tests.md)               | Disallow disabled tests                                         | ![recommended](https://img.shields.io/badge/-recommended-lightgrey.svg) |                                                             |
 | [no-focused-tests](docs/rules/no-focused-tests.md)                 | Disallow focused tests                                          | ![recommended](https://img.shields.io/badge/-recommended-lightgrey.svg) |                                                             |
 | [no-identical-title](docs/rules/no-identical-title.md)             | Disallow identical titles                                       | ![recommended](https://img.shields.io/badge/-recommended-lightgrey.svg) |                                                             |

docs/rules/consistent-test-it.md

@@ -0,0 +1,89 @@
+# Have control over `test` and `it` usages (consistent-test-it)
+
+Jest allows you to choose how you want to define your tests, using the `it` or
+the `test` keywords, with multiple permutations for each:
+
+* **it:** `it`, `xit`, `fit`, `it.only`, `it.skip`.
+* **test:** `test`, `xtest`, `test.only`, `test.skip`.
+
+This rule gives you control over the usage of these keywords in your codebase.
+
+## Rule Details
+
+This rule can be configured as follows
+
+```js
+{
+    type: 'object',
+    properties: {
+        fn: {
+            enum: ['it', 'test'],
+        },
+        withinDescribe: {
+            enum: ['it', 'test'],
+        },
+    },
+    additionalProperties: false,
+}
+```
+
+#### fn
+
+Decides whether to use `test` or `it`.
+
+#### withinDescribe
+
+Decides whether to use `test` or `it` within a describe scope.
+
+```js
+/*eslint jest/consistent-test-it: ["error", {"fn": "test"}]*/
+
+test('foo'); // valid
+test.only('foo'); // valid
+
+it('foo'); // invalid
+it.only('foo'); // invalid
+```
+
+```js
+/*eslint jest/consistent-test-it: ["error", {"fn": "it"}]*/
+
+it('foo'); // valid
+it.only('foo'); // valid
+
+test('foo'); // invalid
+test.only('foo'); // invalid
+```
+
+```js
+/*eslint jest/consistent-test-it: ["error", {"fn": "it", "withinDescribe": "test"}]*/
+
+it('foo'); // valid
+describe('foo', function() {
+  test('bar'); // valid
+});
+
+test('foo'); // invalid
+describe('foo', function() {
+  it('bar'); // invalid
+});
+```
+
+### Default configuration
+
+The default configuration forces top level test to use `test` and all tests
+nested within describe to use `it`.
+
+```js
+/*eslint jest/consistent-test-it: ["error"]*/
+
+test('foo'); // valid
+describe('foo', function() {
+  it('bar'); // valid
+});
+
+it('foo'); // invalid
+describe('foo', function() {
+  test('bar'); // invalid
+});
+```

index.js

@@ -1,5 +1,6 @@
 'use strict';
 
+const consistentTestIt = require('./rules/consistent-test-it');
 const noDisabledTests = require('./rules/no-disabled-tests');
 const noFocusedTests = require('./rules/no-focused-tests');
 const noIdenticalTitle = require('./rules/no-identical-title');
@@ -57,6 +58,7 @@ module.exports = {
     '.snap': snapshotProcessor,
   },
   rules: {
+    'consistent-test-it': consistentTestIt,
     'no-disabled-tests': noDisabledTests,
     'no-focused-tests': noFocusedTests,
     'no-identical-title': noIdenticalTitle,