Fix #445 test cases for fs.unwatchFile

tests/spec/fs.unwatchFile.spec.js

@@ -0,0 +1,19 @@
+var util = require('../lib/test-utils.js');
+var expect = require('chai').expect;
+
+describe('fs.unwatchFile', function() {
+  beforeEach(util.setup);
+  afterEach(util.cleanup);
+
+  it('should be a function', function() {
+    var fs = util.fs();
+    expect(typeof fs.unwatchFile).to.equal('function');
+  });
+
+  it('should not throw an error when using a file not being watched', function() {
+    var fs = util.fs();
+    fs.unwatchFile('/myfile', function(error){
+      expect(error).not.to.exist;
+    });
+  });
+});