java - Mockito + PowerMock - 模拟 Thread.currentThread().getStackTrace()

Question

我目前正在尝试为包验证方法编写 JUnit4 测试。
该方法只是检查调用是否来自正确的包，以确保它不是从外部调用的。方法和RegEx本身可以工作，但是为了安全起见，我想添加一个单元测试。

简单来说，这是包测试:

package foo.bar.lib.util.unsafe;

import java.util.regex.Pattern;

public abstract class UnsafeUtil {
  private static final Pattern UNSAFE_PACKAGE_PATTERN =
      Pattern.compile("^foo\\.bar\\.lib(?:\\..*)?(?<!unsafe)\\.\\w+$");

  protected static void testInternalUse() {
    final StackTraceElement[] stack = Thread.currentThread().getStackTrace();

    for (int i = 2; i < stack.length; ++i) {
      if (UNSAFE_PACKAGE_PATTERN.matcher(stack[i].getClassName()).find()) return;
    }

    throw new IllegalStateException("UnsafeUtil may not be used externally");
  }
}

现在我的测试类如下所示:

package foo.bar.lib.util.unsafe;

import static org.junit.Assert.assertEquals;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mockito;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
@PrepareForTest(Thread.class)
public class UnsafeUtilTest {
  private static final String expectedError = "UnsafeUtil may not be used externally";

  private static void setupStackTrace(String className) {
    final Thread fakeThread = Mockito.mock(Thread.class);
    final StackTraceElement[] fakeStack =
        new StackTraceElement[] {null, null, new StackTraceElement(className, "", "", 0)};

    PowerMockito.mockStatic(Thread.class);
    Mockito.when(Thread.currentThread()).thenReturn(fakeThread);
    Mockito.when(fakeThread.getStackTrace()).thenReturn(fakeStack);
  }

  @Test
  public void correctPackageTest() {
    setupStackTrace("foo.bar.lib.Main");

    try {
      CommonUnsafeUtil.testInternalUse();
    } catch (IllegalStateException e) {
      if (expectedError.equals(e.getMessage()))
        throw new AssertionError("An IllegalStateException should not have been thrown:", e);
    }
  }

  @Test
  public void incorrectPackageTest() {
    setupStackTrace(String.class.getName());

    try {
      CommonUnsafeUtil.testInternalUse();
    } catch (IllegalStateException e) {
      assertEquals(expectedError, e.getMessage());
    }
  }
}

in CorrectPackageTest 成功，但是 CorrectPackageTest 失败并出现以下错误:

java.lang.AssertionError: An IllegalStateException should not have been thrown:
    at foo.bar.lib.util.unsafe.UnsafeUtilTest.correctPackageTest(UnsafeUtilTest.java:36)
    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.internal.runners.TestMethod.invoke(TestMethod.java:68)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:326)
    at org.junit.internal.runners.MethodRoadie$2.run(MethodRoadie.java:89)
    at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:97)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.executeTest(PowerMockJUnit44RunnerDelegateImpl.java:310)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTestInSuper(PowerMockJUnit47RunnerDelegateImpl.java:131)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.access$100(PowerMockJUnit47RunnerDelegateImpl.java:59)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner$TestExecutorStatement.evaluate(PowerMockJUnit47RunnerDelegateImpl.java:147)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.evaluateStatement(PowerMockJUnit47RunnerDelegateImpl.java:107)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTest(PowerMockJUnit47RunnerDelegateImpl.java:82)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:298)
    at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:87)
    at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:50)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.invokeTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:218)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:160)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$1.run(PowerMockJUnit44RunnerDelegateImpl.java:134)
    at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:34)
    at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:44)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:136)
    at org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:117)
    at org.powermock.modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run(AbstractCommonPowerMockRunner.java:57)
    at org.powermock.modules.junit4.PowerMockRunner.run(PowerMockRunner.java:59)
    at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.runTestClass(JUnitTestClassExecutor.java:116)
    at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.execute(JUnitTestClassExecutor.java:59)
    at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.execute(JUnitTestClassExecutor.java:39)
    at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestClassProcessor.processTestClass(AbstractJUnitTestClassProcessor.java:66)
    at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:51)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:32)
    at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:93)
    at com.sun.proxy.$Proxy1.processTestClass(Unknown Source)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.processTestClass(TestWorker.java:109)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:146)
    at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:128)
    at org.gradle.internal.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:404)
    at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
    at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.IllegalStateException: UnsafeUtil may not be used externally
    at foo.bar.lib.util.unsafe.UnsafeUtil.testInternalUse(UnsafeUtil.java:17)
    at foo.bar.lib.util.unsafe.UnsafeUtilTest.correctPackageTest(UnsafeUtilTest.java:33)
    ... 56 more

经过进一步检查，我发现 Thread.currentThread().getStackTrace() 调用返回两个调用的真实堆栈跟踪，而不是我创建的模拟堆栈跟踪。

我做错了什么？

Answer 1

PowerMock 将要求您为该模拟准备被测试的类。除非您完全理解将要发生的字节码操作，否则有时可能会很偶然，具体取决于您想要做什么。

来自PrepareForTest的文档

This includes final classes, classes with final, private, static or native methods that should be mocked and also classes that should be return a mock object upon instantiation.

https://static.javadoc.io/org.powermock/powermock-core/1.6.5/org/powermock/core/classloader/annotations/PrepareForTest.html

在这种情况下，需要准备UnsafeUtil。