Allow customizing the name of the input file in fixtures (overriding code.js)

README.md

@@ -97,6 +97,34 @@ fixtures('my plugin', path.join(__dirname, '__fixtures__'), {
 
 By default, it will compare the outputs with the files on the filesystem and you have to manually update the files in case of a mismatch. If you're using Jest, you can use the snapshot feature to automatically update the files with a keypress. ([See below](#integration-with-jest-snapshot)) on how to set it up.
 
+### Customizing the test file name
+
+Sometimes, the name of the test file can be relevant to the test itself. In that case, the default name of `code.js` can be overridden by specifying a `babel-test.json` configuration file inside the fixture directory:
+
+```sh
+.
+├── function-expression
+│   ├── code.js
+│   └── output.js
+├── invalid-syntax
+│   ├── code.js
+│   └── error.js
+└── simple-variable
+    ├── babel-test.json
+    ├── input.js
+    └── output.js
+```
+
+The configuration file supports a single option: `inputFileName`, which specifies the name to use instead of `code.js`.
+
+```json
+{
+  "inputFileName": "input.js"
+}
+```
+
+The name of `output.js` cannot be overridden.
+
 ### Standalone test
 
 To run a standalone test with some custom logic, you can use the `test` function returned from `create`:

src/__fixtures__/custom-file-name/babel-test.json

@@ -0,0 +1,3 @@
+{
+  "inputFileName": "input.js"
+}

src/__fixtures__/custom-file-name/input.js

@@ -0,0 +1 @@
+var title = 'hello world';

src/__fixtures__/custom-file-name/output.js

@@ -0,0 +1 @@
+var eltit = 'hello world';

src/index.js

@@ -78,7 +78,9 @@ exports.create = function create(config) {
           : it;
 
         t(f.replace(/^(skip|only)\./, '').replace(/(-|_)/g, ' '), () => {
-          const filename = path.join(path.join(directory, f), 'code.js');
+          const testDirectory = path.join(directory, f);
+          const testConfig = loadTestConfig(testDirectory);
+          const filename = path.join(testDirectory, testConfig.inputFileName);
           const content = fs.readFileSync(filename, 'utf8');
 
           return Promise.resolve(callback(content, { filename })).then(
@@ -228,3 +230,17 @@ exports.create = function create(config) {
 
   return { test, fixtures };
 };
+
+function loadTestConfig(directory) {
+  const configFilename = path.join(directory, 'babel-test.json');
+  const defaultConfig = {
+    inputFileName: 'code.js',
+  };
+
+  try {
+    const config = JSON.parse(fs.readFileSync(configFilename, 'utf8'));
+    return Object.assign(defaultConfig, config);
+  } catch (_) {
+    return defaultConfig;
+  }
+}