当在equals（）/ hashCode（）中调用模拟方法时，Mockito会产生StackOverflowError

Question

此示例代码：

public final class FooBarTest {
    @Test
    public void test() {
        final Foo foo = mock(Foo.class);
        when(foo.getBar()).thenReturn(1);
        new HashSet().add(foo);
    }

    private class Foo {
        @Override
        public final boolean equals(final Object other) {
            return getBar() == 0;
        }

        public int getBar() {
            return 0;
        }

        @Override
        public final int hashCode() {
            return getBar();
        }
    }
}

产生无限循环并引发异常：

java.lang.StackOverflowError
    at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:57)
    at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:43)
    at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor$DispatcherDefaultingToRealMethod.interceptSuperCallable(MockMethodInterceptor.java:119)
    at de.weltraumschaf.maconha.FooBarTest$Foo$MockitoMock$217383798.getBar(Unknown Source)
    at de.weltraumschaf.maconha.FooBarTest$Foo.equals(FooBarTest.java:24)
    at org.mockito.internal.invocation.InvocationMatcher.matches(InvocationMatcher.java:81)
    at org.mockito.internal.stubbing.InvocationContainerImpl.findAnswerFor(InvocationContainerImpl.java:82)
    at org.mockito.internal.handler.MockHandlerImpl.handle(MockHandlerImpl.java:90)
    at org.mockito.internal.handler.NullResultGuardian.handle(NullResultGuardian.java:32)
    at org.mockito.internal.handler.InvocationNotifierHandler.handle(InvocationNotifierHandler.java:36)
    at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:57)
    at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:43)
    at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor$DispatcherDefaultingToRealMethod.interceptSuperCallable(MockMethodInterceptor.java:119)
    at de.weltraumschaf.maconha.FooBarTest$Foo$MockitoMock$217383798.getBar(Unknown Source)
    at de.weltraumschaf.maconha.FooBarTest$Foo.equals(FooBarTest.java:24)
    at org.mockito.internal.invocation.InvocationMatcher.matches(InvocationMatcher.java:81)
    at org.mockito.internal.stubbing.InvocationContainerImpl.findAnswerFor(InvocationContainerImpl.java:82)
    at org.mockito.internal.handler.MockHandlerImpl.handle(MockHandlerImpl.java:90)
    at org.mockito.internal.handler.NullResultGuardian.handle(NullResultGuardian.java:32)
    at org.mockito.internal.handler.InvocationNotifierHandler.handle(InvocationNotifierHandler.java:36)
    at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:57)
    at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:43)
    at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor$DispatcherDefaultingToRealMethod.interceptSuperCallable(MockMethodInterceptor.java:119)
    at de.weltraumschaf.maconha.FooBarTest$Foo$MockitoMock$217383798.getBar(Unknown Source)
    at de.weltraumschaf.maconha.FooBarTest$Foo.equals(FooBarTest.java:24)
    ...

我调试了代码，迷失在Mockito的深处。 我唯一看到的是equals方法被称为right。 我知道Mockito不存根equals / hashCode / toString 。 我也很清楚，HashSet调用equals方法来查看其中是否已经有一个equal元素。 但是我不明白的是：为什么这个循环是无止境的？

使用的Mockito版本是2.8.9和JUnit 4.12。

Answer 1

因为在调用org.mockito.internal.invocation.InvocationMatcher#matches有org.mockito.internal.invocation.InvocationMatcher#matches ，基本上是
invocation.getMock().equals(candidate.getMock()) （ invocation.getMock()是您的getBar Foo实例），这会导致对getBar的调用， getBar该getBar被嘲笑会导致对equals -> getBar >模拟-> equals -> getBar >等等...