Add support for addFiles config parameter.

README.md

@@ -61,7 +61,10 @@ In `package.json`
   "jest-runner-mocha": {
     "cliOptions": {
       // Options here
-    }
+    },
+    "addFiles": [
+      // Absolute file paths
+    ],
   }
 }
 ```
@@ -71,7 +74,10 @@ or in `jest-runner-mocha.config.js`
 module.exports = {
   cliOptions: {
     // Options here
-  }
+  },
+  addFiles: [
+    // Absolute file paths
+  ],
 }
 ```
 
@@ -86,6 +92,12 @@ jest-runner-mocha maps some mocha CLI arguments to config options. For example `
 |timeout|`"timeout": 10000`
 |compiler|`"compiler": "./path/to/babel-register"`
 
+### addFiles
+
+If you want to include additional files (for example additional Mocha setup code), you can list the files that you want added.
+
+This value can be a string or an array of absolute file paths.
+
 ### Coverage
 
 Coverage works outside of the box, simply `yarn jest -- --coverage`

src/runMocha.js

@@ -4,7 +4,7 @@ const setupCollectCoverage = require('./utils/setupCollectCoverage');
 const getMochaOptions = require('./utils/getMochaOptions');
 
 const runMocha = ({ config, testPath, globalConfig }, workerCallback) => {
-  const { cliOptions: mochaOptions } = getMochaOptions(config);
+  const { cliOptions: mochaOptions, addFiles } = getMochaOptions(config);
 
   class Reporter extends Mocha.reporters.Base {
     constructor(runner) {
@@ -56,6 +56,7 @@ const runMocha = ({ config, testPath, globalConfig }, workerCallback) => {
     coveragePathIgnorePatterns: config.coveragePathIgnorePatterns,
   });
 
+  addFiles.forEach(file => mocha.addFile(file));
   mocha.addFile(testPath);
 
   const onEnd = () => {

src/utils/getMochaOptions.js

@@ -3,14 +3,19 @@ const cosmiconfig = require('cosmiconfig');
 
 const explorer = cosmiconfig('jest-runner-mocha', { sync: true });
 
-const normalize = (jestConfig, { cliOptions: rawCliOptions = {} }) => {
+const normalize = (
+  jestConfig,
+  { cliOptions: rawCliOptions = {}, addFiles: rawAddFiles = [] },
+) => {
   const cliOptions = Object.assign({}, rawCliOptions);
 
   if (cliOptions.compiler && !path.isAbsolute(cliOptions.compiler)) {
     cliOptions.compiler = path.resolve(jestConfig.rootDir, cliOptions.compiler);
   }
 
-  return { cliOptions };
+  const addFiles = [].concat(rawAddFiles);
+
+  return { cliOptions, addFiles };
 };
 
 const getMochaOptions = jestConfig => {