Android Studio 3.2 Canary 2
Build #AI-173.4591728, built on February 8, 2018
JRE: 1.8.0_152-release-1024-b01 amd64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Linux 4.14.18-300.fc27.x86_64

我有以下 Activity ，我想对 fragment 已附加并应返回非空值的情况进行单元测试。并且应该属于else条件:

这是我的 Activity :

public class BillingActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.billing_container);

        if(getSupportFragmentManager().findFragmentByTag(BillingView.TAG) == null) {
            final FragmentTransaction fragmentTransaction =
                    getSupportFragmentManager().beginTransaction();

            fragmentTransaction.add(
                    R.id.billing_view_container,
                    BillingView.newInstance(),
                    BillingView.TAG);

            fragmentTransaction.commit();
        }
        else {
            Timber.d("Fragment already attached");
        }
    }
}

测试类是这样的:我可以编写附加 fragment 的测试，但我想测试 fragment 已经附加并且应该返回非空的条件。

class BillingActivityTest: BaseRobolectricTestRunner() {
    private lateinit var billingActivity: BillingActivity

    @Before
    fun setup() {
        billingActivity = Robolectric.buildActivity(BillingActivity::class.java)
                .create()
                .start()
                .get()
    }

    @Test
    fun testBillingActivityIsNotNullValue() {
        assertThat(billingActivity, `is`(notNullValue()))
    }

    @Test
    fun testBillingFragmentHasStarted() {
        val actualFragment = billingActivity
                .supportFragmentManager
                .findFragmentByTag(BillingView.TAG)

        assertThat(actualFragment.tag, `is`(BillingView.TAG))
    }

    @Test
    fun testBillingFragmentAlreadyAttached() {
        /* how to test */
    }
}

感谢您的任何建议，

最佳答案

方法you've chosen (使用 recreate() )只要它复制您请求的行为就可以工作。我相信这是目前最短的方法。

尽管如此，我不能认为它是一个纯粹的单元测试，因为实际上你在作弊，因为显然你对 Activity 的 recreate() Action 不感兴趣(不妨来有副作用)。

如果您想执行纯单元测试，那么这里就是执行此操作的方法。声明 Activity 如下:

    class MainActivity : AppCompatActivity() {

        internal var fragmentManagerRetriever = FragmentManagerRetriever()

        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)

            val fragmentManager = fragmentManagerRetriever.getFragmentManager(this)
            if (fragmentManager.findFragmentByTag("TAG") == null) {
                val fragmentTransaction = fragmentManager.beginTransaction()
                fragmentTransaction.add(SomeFragment(), "TAG")
                fragmentTransaction.commit()
            }
        }

    }

FragmentManagerRetriever 就这么简单:

    class FragmentManagerRetriever {

        public FragmentManager getFragmentManager(FragmentActivity activity) {
            return activity.getSupportFragmentManager();
        }

    }

那么你有一个接缝来执行纯单元测试:

    @Test
    fun nullCase() {
        val activityController = Robolectric.buildActivity(MainActivity::class.java)
        val activity = activityController.get()

        val fragmentManagerRetriever = mock(FragmentManagerRetriever::class.java)
        val fragmentManager = mock(FragmentManager::class.java)
        val fragmentTransaction = mock(FragmentTransaction::class.java)
        activity.fragmentManagerRetriever = fragmentManagerRetriever

        `when`(fragmentManagerRetriever.getFragmentManager(activity)).thenReturn(fragmentManager)
        `when`(fragmentManager.findFragmentByTag("TAG")).thenReturn(null)
        `when`(fragmentManager.beginTransaction()).thenReturn(fragmentTransaction)

        activityController.create()

        val inOrder = Mockito.inOrder(fragmentTransaction)
        inOrder.verify(fragmentTransaction).add(ArgumentMatchers.any(SomeFragment::class.java), ArgumentMatchers.eq("TAG"))
        inOrder.verify(fragmentTransaction).commit()
    }

以及对非空情况的测试:

    @Test
    fun nonNullCase() {
        val activityController = Robolectric.buildActivity(MainActivity::class.java)
        val activity = activityController.get()

        val fragmentManagerRetriever = mock(FragmentManagerRetriever::class.java)
        val fragmentManager = mock(FragmentManager::class.java)
        val fragmentTransaction = mock(FragmentTransaction::class.java)
        activity.fragmentManagerRetriever = fragmentManagerRetriever

        `when`(fragmentManagerRetriever.getFragmentManager(activity)).thenReturn(fragmentManager)
        `when`(fragmentManager.findFragmentByTag("TAG")).thenReturn(mock(Fragment::class.java))

        activityController.create()

        verifyZeroInteractions(fragmentTransaction)
    }

关于android - findFragmentByTag 的单元测试条件，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/48812927/