jest-haste-map: mock 'fs' with more idiomatic jest.mock() (jestjs#4046)

packages/jest-haste-map/src/__tests__/index.test.js

@@ -60,6 +60,34 @@ jest.mock('sane', () => {
   };
 });
 
+let mockChangedFiles;
+let mockFs;
+
+jest.mock('graceful-fs', () => ({
+  readFileSync: jest.fn((path, options) => {
+    expect(options).toBe('utf8');
+
+    // A file change can be triggered by writing into the
+    // mockChangedFiles object.
+    if (mockChangedFiles && path in mockChangedFiles) {
+      return mockChangedFiles[path];
+    }
+
+    if (mockFs[path]) {
+      return mockFs[path];
+    }
+
+    const error = new Error(`Cannot read path '${path}'.`);
+    error.code = 'ENOENT';
+    throw error;
+  }),
+  writeFileSync: jest.fn((path, data, options) => {
+    expect(options).toBe('utf8');
+    mockFs[path] = data;
+  }),
+}));
+jest.mock('fs', () => require('graceful-fs'));
+
 const skipOnWindows = require('skipOnWindows');
 
 const cacheFilePath = '/cache-file';
@@ -68,14 +96,10 @@ let defaultConfig;
 let fs;
 let H;
 let HasteMap;
-let mockChangedFiles;
 let mockClocks;
 let mockEmitters;
-let mockFs;
 let object;
-let readFileSync;
 let workerFarmMock;
-let writeFileSync;
 
 describe('HasteMap', () => {
   skipOnWindows.suite();
@@ -121,29 +145,6 @@ describe('HasteMap', () => {
     mockChangedFiles = null;
 
     fs = require('graceful-fs');
-    readFileSync = fs.readFileSync;
-    writeFileSync = fs.writeFileSync;
-    fs.readFileSync = jest.fn((path, options) => {
-      expect(options).toBe('utf8');
-
-      // A file change can be triggered by writing into the
-      // mockChangedFiles object.
-      if (mockChangedFiles && path in mockChangedFiles) {
-        return mockChangedFiles[path];
-      }
-
-      if (mockFs[path]) {
-        return mockFs[path];
-      }
-
-      const error = new Error(`Cannot read path '${path}'.`);
-      error.code = 'ENOENT';
-      throw error;
-    });
-    fs.writeFileSync = jest.fn((path, data, options) => {
-      expect(options).toBe('utf8');
-      mockFs[path] = data;
-    });
 
     consoleWarn = console.warn;
     console.warn = jest.fn();
@@ -167,8 +168,6 @@ describe('HasteMap', () => {
 
   afterEach(() => {
     console.warn = consoleWarn;
-    fs.readFileSync = readFileSync;
-    fs.writeFileSync = writeFileSync;
   });
 
   it('exports constants', () => {