Mostly tests and some small changes (#16)

* Create docker.test.ts
* Add context tests
* test main

__tests__/docker.test.ts

@@ -0,0 +1,49 @@
+import {loginStandard, logout} from '../src/docker';
+
+import * as path from 'path';
+
+import * as exec from '@actions/exec';
+
+process.env['RUNNER_TEMP'] = path.join(__dirname, 'runner');
+
+test('loginStandard calls exec', async () => {
+  const execSpy: jest.SpyInstance = jest.spyOn(exec, 'exec');
+  // don't let exec try to actually run the commands
+  execSpy.mockImplementation(() => {});
+
+  const username: string = 'dbowie';
+  const password: string = 'groundcontrol';
+  const registry: string = 'https://ghcr.io';
+
+  await loginStandard(registry, username, password);
+
+  expect(execSpy).toHaveBeenCalledWith(`docker`, ['login', '--password-stdin', '--username', username, registry], {
+    input: Buffer.from(password),
+    silent: true,
+    ignoreReturnCode: true,
+    listeners: expect.objectContaining({
+      stdout: expect.any(Function),
+      stderr: expect.any(Function)
+    })
+  });
+});
+
+test('logout calls exec', async () => {
+  const execSpy: jest.SpyInstance = jest.spyOn(exec, 'exec');
+  // don't let exec try to actually run the commands
+  execSpy.mockImplementation(() => {});
+
+  const registry: string = 'https://ghcr.io';
+
+  await logout(registry);
+
+  expect(execSpy).toHaveBeenCalledWith(`docker`, ['logout', registry], {
+    silent: false,
+    ignoreReturnCode: true,
+    input: Buffer.from(''),
+    listeners: expect.objectContaining({
+      stdout: expect.any(Function),
+      stderr: expect.any(Function)
+    })
+  });
+});