Don't invoke expect.extend (#333)

Author: keeganwitt

README.md

@@ -135,11 +135,31 @@ yarn add -D jest-extended
 
 Note that `jest-extended` only supports Jest version 24 and newer.
 
-Add `jest-extended` to your Jest `setupFilesAfterEnv` configuration. [See for help](https://jestjs.io/docs/en/configuration.html#setupfilesafterenv-array)
+```javascript
+// ./testSetup.js
+
+// add all jest-extended matchers
+import * as matchers from 'jest-extended';
+expect.extend(matchers);
+
+// or just add specific matchers
+import { toBeArray, toBeSealed } from 'jest-extended';
+expect.extend({ toBeArray, toBeSealed });
+```
+
+Add your setup script to your Jest `setupFilesAfterEnv` configuration. [See for help](https://jestjs.io/docs/en/configuration.html#setupfilesafterenv-array)
+
+```json
+"jest": {
+  "setupFilesAfterEnv": ["./testSetup.js"]
+}
+```
+
+To automatically extend `expect` with all matchers, you can use
 
 ```json
 "jest": {
-  "setupFilesAfterEnv": ["jest-extended"]
+  "setupFilesAfterEnv": ["jest-extended/all"]
 }
 ```
 

all.js

@@ -0,0 +1 @@
+require('./dist/all');

src/all/index.js

@@ -0,0 +1,13 @@
+import * as matchers from '../matchers';
+
+const jestExpect = global.expect;
+
+if (jestExpect !== undefined) {
+  jestExpect.extend(matchers);
+} else {
+  throw new Error(
+    "Unable to find Jest's global expect. " +
+      'Please check you have added jest-extended correctly to your jest configuration. ' +
+      'See https://github.com/jest-community/jest-extended#setup for help.',
+  );
+}

src/index.js

@@ -1,15 +1 @@
-import * as matchers from './matchers';
-
-const jestExpect = global.expect;
-
-if (jestExpect !== undefined) {
-  jestExpect.extend(matchers);
-} else {
-  /* eslint-disable no-console */
-  console.error(
-    "Unable to find Jest's global expect." +
-      '\nPlease check you have added jest-extended correctly to your jest configuration.' +
-      '\nSee https://github.com/jest-community/jest-extended#setup for help.',
-  );
-  /* eslint-enable no-console */
-}
+export * from './matchers';