ADD unit tests, split and refactor source code

__test__/assets/binary.spec.js

@@ -0,0 +1,51 @@
+const fs = require('fs');
+const common = require('../../src/common');
+const verifyAndPlaceBinary = require('../../src/assets/binary');
+
+jest.mock('fs');
+jest.mock('../../src/common');
+
+describe('verifyAndPlaceBinary()', () => {
+  let callback;
+
+  beforeEach(() => {
+    callback = jest.fn();
+  });
+
+  it('should call callback with error if binary downloaded differs from config', () => {
+    fs.existsSync.mockReturnValueOnce(false);
+
+    verifyAndPlaceBinary('command', './bin', callback);
+
+    expect(callback).toHaveBeenCalledWith('Downloaded binary does not contain the binary specified in configuration - command');
+  });
+
+  it('should call callback with error if installation path cannot be found', () => {
+    const error = new Error();
+
+    fs.existsSync.mockReturnValueOnce(true);
+    common.getInstallationPath.mockImplementationOnce((cb) => cb(error));
+
+    verifyAndPlaceBinary('command', './bin', callback);
+
+    expect(callback).toHaveBeenCalledWith(error);
+  });
+
+  it('should call callback with null on success', () => {
+    fs.existsSync.mockReturnValueOnce(true);
+    common.getInstallationPath.mockImplementationOnce((cb) => cb(null, '/usr/local/bin'));
+
+    verifyAndPlaceBinary('command', './bin', callback);
+
+    expect(callback).toHaveBeenCalledWith(null);
+  });
+
+  it('should move the binary to installation directory', () => {
+    fs.existsSync.mockReturnValueOnce(true);
+    common.getInstallationPath.mockImplementationOnce((cb) => cb(null, '/usr/local/bin'));
+
+    verifyAndPlaceBinary('command', './bin', callback);
+
+    expect(fs.renameSync).toHaveBeenCalledWith('bin/command', '/usr/local/bin/command');
+  });
+});