Fix issue #398 - Add testing for promises to all test cases in fs.writeFile-readFile.spec.js file (#402)

* Fix issue #398 - Add testing for promises to all test cases in fs.writeFile-readFile.spec.js file

* Fix issue #398 - Add testing for promises to all test cases in fs.writeFile-readFile.spec.js file

* Fixed requested issues

* Further Improvement

tests/spec/fs.writeFile-readFile.spec.js

@@ -112,3 +112,91 @@ describe('fs.writeFile, fs.readFile', function() {
     });
   });
 });
+
+/**
+ * fsPromises tests
+ */
+
+describe('fsPromises.writeFile, fsPromises.readFile', function() {
+  beforeEach(util.setup);
+  afterEach(util.cleanup);
+
+  it('should be a function', function() {
+    var fsPromises = util.fs().promises;
+    expect(fsPromises.writeFile).to.be.a('function');
+    expect(fsPromises.readFile).to.be.a('function');
+  });
+
+  it('should return a promise', function() {
+    var fsPromises = util.fs().promises;
+    var contents = 'This is a file.';
+
+    var p = fsPromises.writeFile('/myfile', contents);
+    expect(p).to.be.a('Promise');
+
+    p.then(() => {
+      expect(fsPromises.readFile('/myfile', 'utf8')).to.be.a('Promise');
+    });
+    return p;
+  });
+
+  it('should error when path is wrong to readFile', function() {
+    var fsPromises = util.fs().promises;
+
+    return fsPromises.readFile('/no-such-file', 'utf8')
+      .catch(error => { 
+        expect(error).to.exist; 
+        expect(error.code).to.equal('ENOENT'); 
+      });
+  });
+
+  it('should write, read a utf8 file without specifying utf8 in writeFile', function() {
+    var fsPromises = util.fs().promises;
+    var contents = 'This is a file.';
+
+    return fsPromises.writeFile('/myfile', contents)
+      .then( () => fsPromises.readFile('/myfile', 'utf8'))
+      .then(data => { expect(data).to.equal(contents); });
+  });
+
+  it('should write, read a utf8 file with "utf8" option to writeFile', function() {
+    var fsPromises = util.fs().promises;
+    var contents = 'This is a file.';
+
+    return fsPromises.writeFile('/myfile', contents, 'utf8') 
+      .then( () => fsPromises.readFile('/myfile', 'utf8'))
+      .then(data => { expect(data).to.equal(contents); });
+  });
+
+  it('should write, read a utf8 file with {encoding: "utf8"} option to writeFile', function() {
+    var fsPromises = util.fs().promises;
+    var contents = 'This is a file.';
+
+    return fsPromises.writeFile('/myfile', contents, { encoding: 'utf8' })
+      .then( () => fsPromises.readFile('/myfile', 'utf8'))
+      .then(data => { expect(data).to.equal(contents); });
+  });
+
+  it('should write, read a binary file', function() {
+    var fsPromises = util.fs().promises;
+    // String and utf8 binary encoded versions of the same thing: 'This is a file.'
+    var binary = new Buffer([84, 104, 105, 115, 32, 105, 115, 32, 97, 32, 102, 105, 108, 101, 46]);
+
+    return fsPromises.writeFile('/myfile', binary)
+      .then( () => fsPromises.readFile('/myfile'))
+      .then(data => { expect(data).to.deep.equal(binary); });
+  });
+
+  it('should follow symbolic links', function() {
+    var fsPromises = util.fs().promises;
+    var contents = 'This is a file.';
+
+    return fsPromises.writeFile('/myfile', '', { encoding: 'utf8' })
+      .then( () => fsPromises.symlink('/myfile', '/myFileLink'))
+      .then( () => fsPromises.writeFile('/myFileLink', contents, 'utf8'))
+      .then( () => fsPromises.readFile('/myFileLink', 'utf8'))
+      .then(data => { expect(data).to.equal(contents); });
+  });
+});
+
+