feat(jest): create Jest danger plugin (#1)

Author: macklinu

README.md

@@ -1,3 +1,81 @@
 # danger-plugin-jest
 
-TODO
+[![Build Status](https://travis-ci.org/macklinu/danger-plugin-jest.svg?branch=master)](https://travis-ci.org/macklinu/danger-plugin-jest)
+[![npm version](https://badge.fury.io/js/danger-plugin-jest.svg)](https://badge.fury.io/js/danger-plugin-jest)
+[![semantic-release](https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg)](https://github.com/semantic-release/semantic-release)
+
+> [Danger](https://github.com/danger/danger-js) plugin for Jest
+
+## Usage
+
+### Setup Jest
+
+This Danger plugin relies on modifying your Jest configuration.
+
+Install [jest-json-reporter](https://github.com/Vall3y/jest-json-reporter):
+
+```sh
+yarn add jest-json-reporter --dev
+```
+
+Modify your `package.json` to process test results with jest-json-reporter. You may optionally set the output path of the JSON test results using the `jestJsonReporter.outputFile` path (which otherwise defaults to `./test-results.json`):
+
+```json
+{
+  "jest": {
+    "testResultsProcessor": "jest-json-reporter"
+  },
+  "jestJsonReporter": {
+    "outputFile": "tests/results.json"
+  }
+}
+```
+
+> You may also want to add the JSON output file to your `.gitignore`, since it doesn't need to be checked into source control.
+
+### Setup Danger
+
+Install this Danger plugin:
+
+```sh
+yarn add danger-plugin-jest --dev
+```
+
+If you set `jestJsonReporter.outputFile` in your `package.json`, make sure that `testResultsJsonPath` matches that path:
+
+```js
+// dangerfile.js
+import path from 'path'
+import jest from 'danger-plugin-jest'
+
+jest({
+  testResultsJsonPath: path.resolve(__dirname, 'tests/results.json'),
+})
+```
+
+If you _did not_ change the `jestJsonReporter.outputFile` path in your `package.json`, you can just do the following:
+
+```js
+// dangerfile.js
+import jest from 'danger-plugin-jest'
+
+jest()
+```
+
+See [`src/index.ts`](https://github.com/macklinu/danger-plugin-jest/blob/master/src/index.ts) for more details.
+
+## Changelog
+
+See the GitHub [release history](https://github.com/macklinu/danger-plugin-jest/releases).
+
+## Development
+
+Install [Yarn](https://yarnpkg.com/en/), and install the dependencies - `yarn install`.
+
+Run the [Jest](https://facebook.github.io/jest/) test suite with `yarn test`.
+
+This project uses [semantic-release](https://github.com/semantic-release/semantic-release) for automated NPM package publishing.
+
+The main caveat: instead of running `git commit`, run `yarn commit` and follow the prompts to input a conventional changelog message via [commitizen](https://github.com/commitizen/cz-cli).
+
+:heart:

__tests__/index.test.ts

@@ -12,7 +12,7 @@
     "commit": "git-cz",
     "commitmsg": "validate-commit-msg",
     "build": "tsc -p tsconfig.json",
-    "lint": "tslint '{__tests__/**/*.test.ts,src/**/*.ts}' -c tslint.json -p tsconfig.json",
+    "lint": "tslint 'src/**/*.ts' -c tslint.json -p tsconfig.json",
     "test": "jest",
     "docs": "typedoc --theme minimal --out docs src/index.ts",
     "docs:serve": "npm run docs && serve docs",
@@ -72,7 +72,7 @@
     }
   },
   "lint-staged": {
-    "{__tests__/**/*.test.ts,src/**/*.ts}": [
+    "src/**/*.ts": [
       "tslint -c tslint.json -p tsconfig.json --fix",
       "git add"
     ]

package.json

@@ -0,0 +1,13 @@
+/**
+ * A simple formatter that formats only test failures for use by Danger.
+ */
+export class TestFailureFormatter {
+  constructor(private results: any) {}
+
+  public format(): string {
+    return this.results.testResults
+      .filter((r: any) => r.failureMessage)
+      .map((r: any) => r.failureMessage)
+      .join('\n')
+  }
+}