使用 Context.getApplicationContext() 进行 Android JUnit 测试

Question

我目前正在研究一个 android Room Persistency数据库项目。我已经成功实现了所有功能，现在正在尝试为这些功能编写单元测试。这些单元测试依赖于调用以下函数（单例构造函数；我用注释标记了两行重要的行）：

@Database(entities = {RippleModel.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {

    public abstract RippleModelDao rippleModelDao();

    private static AppDatabase INSTANCE; //Used for the singleton

    public static AppDatabase getDatabase(Context context) { //THIS LINE
        if (INSTANCE == null) {
            INSTANCE = Room.databaseBuilder(
                            context.getApplicationContext(),
                            AppDatabase.class, "ripple_db"
                        ).build(); //STACKTRACE SHOWS HERE
        }
        return INSTANCE;
    }
}

我当前的单元测试如下所示：

@RunWith(MockitoJUnitRunner.class)
public class DatabaseUnitTest extends InstrumentationTestCase {

    @Mock
    Context mMockContext = new MockContext();


    @Test
    public void testImportDatabase() throws Exception {
        System.out.println("Importing database..");
        System.out.println(mMockContext);
        System.out.println(mMockContext == null);
        AppDatabase appDatabase = AppDatabase.getDatabase(mMockContext);
    }

}

但是，在使用 Mockito 运行此单元测试时，出现以下错误：

java.lang.IllegalArgumentException：无法为数据库提供空上下文。

at android.arch.persistence.room.RoomDatabase$Builder.build(RoomDatabase.java:441)
at io.turtlesquad.ripplebt.data.AppDatabase.getDatabase(AppDatabase.java:20)
at io.turtlesquad.ripplebt.DatabaseUnitTest.testImportDatabase(DatabaseUnitTest.java:43)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMainV2.main(AppMainV2.java:131)

我已经使用“== null”检查了 Mockito 上下文是否不为空，但情况并非如此（创建的上下文不为空）。

我正在尝试使用 Mockito 模拟上下文，但不确定我在这里做错了什么。Mockito 不应该模拟上下文吗？有什么我想念的吗？

Answer 1

我已经通过更换解决同一个问题context.getApplicationContext()与context从参数getDatabase(.....)的方法AppDatabase class

将您的 AppDatabase java 文件替换为以下代码：

@Database(entities = {RippleModel.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {

public abstract RippleModelDao rippleModelDao();

private static AppDatabase INSTANCE; //Used for the singleton

public static AppDatabase getDatabase(Context context) { //THIS LINE
    if (INSTANCE == null) {
        INSTANCE = Room.databaseBuilder(
                        context,
                        AppDatabase.class, "ripple_db"
                    ).build(); //STACKTRACE SHOWS HERE
    }
    return INSTANCE;
}

}