Added plugin testing

config/setupAfterEnv.js

@@ -0,0 +1,3 @@
+import { toMatchFile } from 'jest-file-snapshot';
+
+expect.extend({ toMatchFile });

jest.config.js

@@ -126,7 +126,7 @@ module.exports = {
   // setupFiles: [],
 
   // A list of paths to modules that run some code to configure or set up the testing framework before each test
-  // setupFilesAfterEnv: [],
+  setupFilesAfterEnv: ['./config/setupAfterEnv.js'],
 
   // A list of paths to snapshot serializer modules Jest should use for snapshot testing
   // snapshotSerializers: [],
@@ -147,9 +147,10 @@ module.exports = {
   // ],
 
   // An array of regexp pattern strings that are matched against all test paths, matched tests are skipped
-  // testPathIgnorePatterns: [
-  //   "\\\\node_modules\\\\"
-  // ],
+  testPathIgnorePatterns: [
+    "\\\\node_modules\\\\",
+    "\\\\__fixtures__\\\\"
+  ],
 
   // The regexp pattern or array of patterns that Jest uses to detect test files
   // testRegex: [],
@@ -181,7 +182,9 @@ module.exports = {
   // verbose: undefined,
 
   // An array of regexp patterns that are matched against all source file paths before re-running tests in watch mode
-  // watchPathIgnorePatterns: [],
+  "watchPathIgnorePatterns": [
+    "__fixtures__\\/[^/]+\\/(output|error)\\.js"
+  ]
 
   // Whether to use watchman for file crawling
   // watchman: true,

package.json

@@ -29,12 +29,14 @@
 		"@babel/parser": "^7.9.6",
 		"@babel/traverse": "^7.9.6",
 		"babel-plugin-tester": "^9.0.1",
-		"jest": "^25.5.4",
+		"babel-test": "^0.2.3",
 		"eslint": "^6.8.0",
+		"eslint-plugin-evelyn": "^2.0.0",
 		"eslint-plugin-mocha": "^5.3.0",
 		"eslint-plugin-node": "^9.2.0",
 		"eslint-plugin-unicorn": "^9.1.1",
-		"eslint-plugin-evelyn": "^2.0.0"
+		"jest": "^25.5.4",
+		"jest-file-snapshot": "^0.3.8"
 	},
 	"dependencies": {
 		"@babel/preset-env": "^7.4.5"

plugin/__tests__/__fixtures__/basic/code.js

@@ -0,0 +1,20 @@
+const global = {prop: "test"};
+
+$shouldNotMutate(['foo']);
+const foo = (foo) => {
+    foo.prop = "pie";
+};
+
+$shouldNotMutate(['foo']);
+function bar(foo) {
+    foo.prop = 'Test';
+}
+
+/**
+ * This does not currently work
+ */
+$shouldNotMutate(['foo']);
+const pizza = foo => console.log(foo);
+
+foo(global);
+bar(global);