Java Mockito卡在单例方法的doReturn中

Question

我有一个单例课程来帮助我从控制台读取输入：

public class IOHelper {
    public org.slf4j.Logger logger = Logger.logger;

    //JLine
    public ConsoleReader cr;

    private static IOHelper instance;

    private IOHelper(){
        {
            try {
                cr = new ConsoleReader();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static synchronized IOHelper getInstance(){
        if (instance == null){
            instance = new IOHelper();
        }

        return instance;
    }

我要测试的代码将其称为：

String in = IOHelper.getInstance().cr.readLine();

然后我的测试课：

class Test {

    private static NetworkCommunicator networkCommunicator;
    private static IOHelper ioHelper;

    @BeforeAll
    static void setUpClass() throws Throwable {

        ioHelper = spy(IOHelper.getInstance());
        doReturn("1").when(ioHelper).cr.readLine();

        networkCommunicator = spy(NetworkCommunicator.class);

        doNothing().when(networkCommunicator).connectToServer();
        doNothing().when(networkCommunicator).connectToOtherServer();
    }

我的测试卡在了doReturn("1").when(ioHelper).cr.readLine(); 行，就好像它实际执行了cr.readline(); 部分。 我的private native int read0() throws IOException;指向private native int read0() throws IOException; 在FileInputStream上找到。 注释表明，如果没有可用的输入，它将阻止。 我想替换控制台上的readLine()方法，因此当CLI要求输入时，测试可以“伪造”该输入。

编辑：2个有趣的线程的调用堆栈：

"main@1" prio=5 tid=0x1 nid=NA runnable
  java.lang.Thread.State: RUNNABLE
     blocks NonBlockingInputStreamThread@1437
      at java.io.FileInputStream.read0(FileInputStream.java:-1)
      at java.io.FileInputStream.read(FileInputStream.java:207)
      at jline.internal.NonBlockingInputStream.read(NonBlockingInputStream.java:166)
      - locked <0x67d> (a jline.internal.NonBlockingInputStream)
      at jline.internal.NonBlockingInputStream.read(NonBlockingInputStream.java:135)
      at jline.internal.NonBlockingInputStream.read(NonBlockingInputStream.java:243)
      at jline.internal.InputStreamReader.read(InputStreamReader.java:257)
      at jline.internal.InputStreamReader.read(InputStreamReader.java:194)
      at jline.console.ConsoleReader.readCharacter(ConsoleReader.java:2147)
      at jline.console.ConsoleReader.readCharacter(ConsoleReader.java:2137)
      at jline.console.ConsoleReader.readBinding(ConsoleReader.java:2222)
      at jline.console.ConsoleReader.readLine(ConsoleReader.java:2463)
      at jline.console.ConsoleReader.readLine(ConsoleReader.java:2374)
      at jline.console.ConsoleReader.readLine(ConsoleReader.java:2362)
      at jline.console.ConsoleReader.readLine(ConsoleReader.java:2350)
      at com.mypkg.Test.setUpClass(Test.java:43)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java:-1)
      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.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:389)
      at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:115)
      at org.junit.jupiter.engine.descriptor.ClassTestDescriptor.lambda$invokeBeforeAllMethods$5(ClassTestDescriptor.java:228)
      at org.junit.jupiter.engine.descriptor.ClassTestDescriptor$$Lambda$162.715378067.execute(Unknown Source:-1)
      at org.junit.jupiter.engine.execution.ThrowableCollector.execute(ThrowableCollector.java:40)
      at org.junit.jupiter.engine.descriptor.ClassTestDescriptor.invokeBeforeAllMethods(ClassTestDescriptor.java:227)
      at org.junit.jupiter.engine.descriptor.ClassTestDescriptor.before(ClassTestDescriptor.java:151)
      at org.junit.jupiter.engine.descriptor.ClassTestDescriptor.before(ClassTestDescriptor.java:61)
      at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.lambda$execute$3(HierarchicalTestExecutor.java:80)
      at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$$Lambda$134.398690014.execute(Unknown Source:-1)
      at org.junit.platform.engine.support.hierarchical.SingleTestExecutor.executeSafely(SingleTestExecutor.java:66)
      at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:77)
      at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.lambda$null$2(HierarchicalTestExecutor.java:92)
      at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$$Lambda$137.1353170030.accept(Unknown Source:-1)
      at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
      at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
      at java.util.Iterator.forEachRemaining(Iterator.java:116)
      at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
      at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
      at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
      at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
      at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
      at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
      at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
      at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.lambda$execute$3(HierarchicalTestExecutor.java:92)
      at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$$Lambda$134.398690014.execute(Unknown Source:-1)
      at org.junit.platform.engine.support.hierarchical.SingleTestExecutor.executeSafely(SingleTestExecutor.java:66)
      at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:77)
      at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:51)
      at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:43)
      at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:170)
      at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:154)
      at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:90)
      at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:62)
      at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
      at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
      at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

"NonBlockingInputStreamThread@1437" daemon prio=5 tid=0xf nid=NA waiting
  java.lang.Thread.State: WAITING
     waiting for main@1 to release lock on <0x67d> (a jline.internal.NonBlockingInputStream)
      at java.lang.Object.wait(Object.java:-1)
      at jline.internal.NonBlockingInputStream.run(NonBlockingInputStream.java:275)
      at java.lang.Thread.run(Thread.java:745)

扩展这个问题：我有一些方法向用户询问多个输入（例如，更新某些设置）。 我是否认为最好的方法是将设置重构为带有参数并仅测试该新方法的方法？ 有一种解决方案，当尝试从ConsoleReader读取任何方法时，我可以将一系列字符串传递给测试按ConsoleReader ？ 我曾考虑过使用Robot但是如果不是通过测试而不是通过底层的逻辑来进行读取，那么如何确保以正确的顺序传递击键呢？

Answer 1

似乎您在嘲笑错误的事情。 您想使用ConsoleReader的收益表。 所以有两个选择：

---

移至在IOHelper类上使用一些getConsoleReader()方法，然后可以将其模拟出来-您需要确保IOHelper类也通过此方法访问此方法。 例如

private final IOHelper mySpy = spy(IOHelper.getInstance());

@Before
public void setup() {
    final ConsoleReader mockCR = mock(ConsoleReader.class);
    // Any mockery on your mockCR you need.
    // doReturn(...).when(mockCR).readLine();, etc.
    doReturn(mockCR).when(mySpy).getConsoleReader();
}

---

将cr字段修改为模拟。 例如

private final IOHelper ioHelper= IOHelper.getInstance();

@Before
public void setup() {
    final ConsoleReader mockCR = mock(ConsoleReader.class);
    // Any mockery on your mockCR you need.
    // doReturn(...).when(mockCR).readLine();, etc.
    ioHelper.cr = mockCR;
}

但是我警告过这种情况。 我看不出将您的ConsoleReader public （或不是final ）的理由，而这仅是一项要求。 您可以始终使用一些帮助程序库来弄乱该字段，即使该字段是私有的也是如此。 spring和apache-commons-lang3均提供此类实用程序。

---

使用Powermock摆弄ConsoleReader的构造ConsoleReader ：

@RunWith(PowerMockRunner.class)
@PrepareForTest(IOHelper.class)
public class IOHelperTest {
    @BeforeClass
    public static void setup() {
        final ConsoleReader mockCR = mock(ConsoleReader.class);
        // Any mockery on your mockCR you need.
        // doReturn(...).when(mockCR).readLine();, etc.

        PowerMock.whenNew(ConsoleReader.class).thenReturn(mockCR);
    }
}

---

最后，您可以修改IOHelper类，以将ConsoleReader用作构造函数参数，并只需通过上述所有方法来提供mockCR即可（并使其不private ）。