feat: create prefer-mock-promise-shorthand rule (#1167)

Author: G-Rath

README.md

@@ -232,6 +232,7 @@ installations requiring long-term consistency.
 | [prefer-hooks-in-order](docs/rules/prefer-hooks-in-order.md)                 | Prefer having hooks in a consistent order                           |                  |              |
 | [prefer-hooks-on-top](docs/rules/prefer-hooks-on-top.md)                     | Suggest having hooks before any test cases                          |                  |              |
 | [prefer-lowercase-title](docs/rules/prefer-lowercase-title.md)               | Enforce lowercase test names                                        |                  | ![fixable][] |
+| [prefer-mock-promise-shorthand](docs/rules/prefer-mock-promise-shorthand.md) | Prefer mock resolved/rejected shorthands for promises               |                  | ![fixable][] |
 | [prefer-snapshot-hint](docs/rules/prefer-snapshot-hint.md)                   | Prefer including a hint with external snapshots                     |                  |              |
 | [prefer-spy-on](docs/rules/prefer-spy-on.md)                                 | Suggest using `jest.spyOn()`                                        |                  | ![fixable][] |
 | [prefer-strict-equal](docs/rules/prefer-strict-equal.md)                     | Suggest using `toStrictEqual()`                                     |                  | ![suggest][] |

docs/rules/prefer-mock-promise-shorthand.md

@@ -0,0 +1,34 @@
+# Prefer mock resolved/rejected shorthands for promises (`prefer-mock-promise-shorthand`)
+
+When working with mocks of functions that return promises, Jest provides some
+API sugar functions to reduce the amount of boilerplate you have to write.
+
+These methods should be preferred when possible.
+
+## Rule Details
+
+The following patterns are warnings:
+
+```js
+jest.fn().mockImplementation(() => Promise.resolve(123));
+jest
+  .spyOn(fs.promises, 'readFile')
+  .mockReturnValue(Promise.reject(new Error('oh noes!')));
+
+myFunction
+  .mockReturnValueOnce(Promise.resolve(42))
+  .mockImplementationOnce(() => Promise.resolve(42))
+  .mockReturnValue(Promise.reject(new Error('too many calls!')));
+```
+
+The following patterns are not warnings:
+
+```js
+jest.fn().mockResolvedValue(123);
+jest.spyOn(fs.promises, 'readFile').mockRejectedValue(new Error('oh noes!'));
+
+myFunction
+  .mockResolvedValueOnce(42)
+  .mockResolvedValueOnce(42)
+  .mockRejectedValue(new Error('too many calls!'));
+```

src/__tests__/__snapshots__/rules.test.ts.snap

@@ -43,6 +43,7 @@ Object {
       "jest/prefer-hooks-in-order": "error",
       "jest/prefer-hooks-on-top": "error",
       "jest/prefer-lowercase-title": "error",
+      "jest/prefer-mock-promise-shorthand": "error",
       "jest/prefer-snapshot-hint": "error",
       "jest/prefer-spy-on": "error",
       "jest/prefer-strict-equal": "error",

src/__tests__/rules.test.ts

@@ -2,7 +2,7 @@ import { existsSync } from 'fs';
 import { resolve } from 'path';
 import plugin from '../';
 
-const numberOfRules = 49;
+const numberOfRules = 50;
 const ruleNames = Object.keys(plugin.rules);
 const deprecatedRules = Object.entries(plugin.rules)
   .filter(([, rule]) => rule.meta.deprecated)