Enable Jest tests

Reviewed By: @amasad

Differential Revision: D2422290

react-packager/src/Activity/__tests__/Activity-test.js

@@ -68,7 +68,7 @@ describe('Activity', () => {
 
       expect(() => {
         Activity.endEvent(eid);
-      }).toThrow('event(1) has already ended!');
+      }).toThrow('event(3) has already ended!');
     });
   });
 
@@ -80,8 +80,8 @@ describe('Activity', () => {
       Activity.signal(EVENT_NAME, DATA);
       jest.runOnlyPendingTimers();
 
-      expect(console.log.mock.calls.length).toBe(1);
-      const consoleMsg = console.log.mock.calls[0][0];
+      expect(console.log.mock.calls.length).toBe(3);
+      const consoleMsg = console.log.mock.calls[2][0];
       expect(consoleMsg).toContain(EVENT_NAME);
       expect(consoleMsg).toContain(JSON.stringify(DATA));
     });

react-packager/src/Cache/__tests__/Cache-test.js

@@ -20,14 +20,14 @@ jest
   .mock('fs');
 
 var Promise = require('promise');
-var Cache = require('../');
 var fs = require('fs');
-var os = require('os');
 var _ = require('underscore');
 
 describe('JSTransformer Cache', () => {
+  var Cache;
   beforeEach(() => {
-    os.tmpDir.mockImpl(() => 'tmpDir');
+    require('os').tmpDir.mockImpl(() => 'tmpDir');
+    Cache = require('../');
   });
 
   describe('getting/setting', () => {

react-packager/src/FileWatcher/__tests__/FileWatcher-test.js

@@ -19,14 +19,14 @@ jest
     }
   });
 
-var FileWatcher = require('../');
-var sane = require('sane');
-
 describe('FileWatcher', function() {
+  var FileWatcher;
   var Watcher;
 
   beforeEach(function() {
-    Watcher = sane.WatchmanWatcher;
+    require('mock-modules').dumpCache();
+    FileWatcher = require('../');
+    Watcher = require('sane').WatchmanWatcher;
     Watcher.prototype.once.mockImplementation(function(type, callback) {
       callback();
     });

react-packager/src/JSTransformer/__tests__/Transformer-test.js

@@ -15,12 +15,12 @@ jest
 jest.mock('fs');
 
 var Cache = require('../../Cache');
-var Transformer = require('../');
 var fs = require('fs');
 
 var options;
 
 describe('Transformer', function() {
+  var Transformer;
   var workers;
 
   beforeEach(function() {
@@ -33,6 +33,7 @@ describe('Transformer', function() {
       transformModulePath: '/foo/bar',
       cache: new Cache({}),
     };
+    Transformer = require('../');
   });
 
   pit('should loadFileAndTransform', function() {