ADD unit tests, split and refactor source code

__test__/assets/move.spec.js

@@ -0,0 +1,49 @@
+const { EventEmitter } = require('events');
+const fs = require('fs');
+const move = require('../../src/assets/move');
+
+jest.mock('fs');
+
+describe('move()', () => {
+
+  let streamEvents, pipe, onSuccess, onError;
+
+  beforeEach(() => {
+
+    streamEvents = new EventEmitter();
+
+    pipe = jest.fn();
+    onSuccess = jest.fn();
+    onError = jest.fn();
+    createWriteStream = jest.fn();
+
+    fs.createWriteStream.mockReturnValueOnce(streamEvents);
+  });
+
+  it('should download resource to given binPath', () => {
+
+    move({ opts: { binPath: './bin', binName: 'command' }, req: { pipe }, onSuccess, onError });
+
+    expect(fs.createWriteStream).toHaveBeenCalledWith('bin/command');
+  });
+
+  it('should call onSuccess on stream closed', () => {
+
+    move({ opts: { binPath: './bin', binName: 'command' }, req: { pipe }, onSuccess, onError });
+
+    streamEvents.emit('close');
+
+    expect(onSuccess).toHaveBeenCalled();
+  });
+
+  it('should call onError with error on write stream error', () => {
+
+    const error = new Error();
+
+    move({ opts: { binPath: './bin', binName: 'command' }, req: { pipe }, onSuccess, onError });
+
+    streamEvents.emit('error', error);
+
+    expect(onError).toHaveBeenCalledWith(error);
+  });
+});