NPE 在第二次调用 Mockito.when 使用自定义参数匹配器时

Question

美好的一天。

假设我有一个接口。该接口有一个接受某些类的一个或两个实例的方法。在单元测试类中，我模拟了这个接口，并希望用这样的逻辑来模拟它：

1. 如果参数与模板 1 匹配，则返回值 1
2. 如果参数与模板 2 匹配，则返回值 2

当我只模拟第一种情况时，测试运行顺利。当我添加第二种情况(以及第一种情况)时，测试会因 NPE 而崩溃，如下所示：

java.lang.NullPointerException
at org.some.pkg.TestTest$ArgMatcher.matches(TestTest.java:54)
at org.some.pkg.TestTest$ArgMatcher.matches(TestTest.java:43)
at org.mockito.internal.invocation.TypeSafeMatching.apply(TypeSafeMatching.java:24)
at org.mockito.internal.invocation.MatcherApplicationStrategy.forEachMatcherAndArgument(MatcherApplicationStrategy.java:83)
at org.mockito.internal.invocation.InvocationMatcher.argumentsMatch(InvocationMatcher.java:152)
at org.mockito.internal.invocation.InvocationMatcher.matches(InvocationMatcher.java:81)
at org.mockito.internal.stubbing.InvocationContainerImpl.findAnswerFor(InvocationContainerImpl.java:91)
at org.mockito.internal.handler.MockHandlerImpl.handle(MockHandlerImpl.java:87)
at org.mockito.internal.handler.NullResultGuardian.handle(NullResultGuardian.java:29)
at org.mockito.internal.handler.InvocationNotifierHandler.handle(InvocationNotifierHandler.java:35)
at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:63)
at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:49)
at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor$DispatcherDefaultingToRealMethod.interceptAbstract(MockMethodInterceptor.java:128)
at org.some.pkg.Interface$MockitoMock$1549778145.callMe(Unknown Source)
at org.some.pkg.TestTest.test(TestTest.java:29)
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.DefaultInternalRunner$1.run(DefaultInternalRunner.java:79)
at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:85)
at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:39)
at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
[MockitoHint] TestTest.test (see javadoc for MockitoHint):
[MockitoHint] 1. Unused... -> at org.some.pkg.TestTest.test(TestTest.java:24)
[MockitoHint]  ...args ok? -> at org.some.pkg.TestTest.test(TestTest.java:29)

Process finished with exit code 255

下面是设置示例。

文件：接口.java -- 模拟接口

package org.some.pkg;
public interface Interface {
public class Arg {
private String str;
private int v;
public Arg(String str, int v) {
this.str = str;
this.v = v;
}
public String getStr() {
return str;
}
public int getV() {
return v;
}
}
int callMe(Arg a1, Arg a2);
}

文件：TestedClass.java -- 一些委托类(实际测试了一个)

package org.some.pkg;
import org.springframework.beans.factory.annotation.Autowired;
public class TestedClass {
@Autowired
Interface delegate;
int callMe(Interface.Arg a1, Interface.Arg a2) {
int x = delegate.callMe(a1, a2);
return x * 2;
}
}

文件：测试测试.java -- 测试

package org.some.pkg;
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.ArgumentMatcher;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.junit.MockitoJUnitRunner;
import static org.mockito.ArgumentMatchers.argThat;
import static org.mockito.Mockito.when;
@RunWith(MockitoJUnitRunner.class)
public class TestTest {
@Mock
private Interface iface;
@InjectMocks
private TestedClass testedClass;
@Test
public void test() {
// when-1
when(iface.callMe(
argThat(new ArgMatcher("start1", 10)),
argThat(new ArgMatcher("start2", 5))
)).thenReturn(10);
// when-2
when(iface.callMe(
argThat(new ArgMatcher("start3", 5)),
argThat(new ArgMatcher("start4", 2))
)).thenReturn(3);
// test
int v = testedClass.callMe(
new Interface.Arg("start1 suffix", 3),
new Interface.Arg("start2, suffix", 4));
System.out.println("V = " + v);
Assert.assertEquals(20, v);
}
class ArgMatcher implements ArgumentMatcher<Interface.Arg> {
private final String start;
private final int threshold;
public ArgMatcher(String start, int threshold) {
this.start = start;
this.threshold = threshold;
}
@Override
public boolean matches(Interface.Arg argument) {
return argument.getV() < threshold && argument.getStr().startsWith(start);
}
}
}

如果我注释掉when-2块，测试运行良好且顺利。否则，我看到一个没有任何明显原因的 NPE。

莫基托的版本是2.24.0 JUnit 的版本为 4。

更新：第二次调用Mockito.when的斗争是一些知识，即模拟方法可以在单个单元测试中多次调用。

Answer 1

使用 mockito 2.28.2 和 3.1.0

：面对类似的问题，解决方案是按照@Morfic提议的方式进行，即重写(假设 Mockito 是静态导入的)：

when(someMock.someMethod(argThat(...))).thenReturn(someValue);

跟：

doReturn(someValue).when(someMock).someMethod(argThat(...));

但是我不知道或解释为什么第一个失败而第二个工作正常......

JUnit 4测试用例显示故障和工作选项：

class MyBean{
public Integer id;
public String name;
public MyBean(int id, String name) {
this.id = id;
this.name = name;
}
}
interface MyService{
Integer measure(MyBean myBean);
}
@Test
public void testThatFailsWithNPE(){
when(myService.measure(argThat((mb) -> Objects.equals(mb.id, 123) && Objects.equals(mb.name, "123")))).thenReturn(123);
when(myService.measure(argThat((mb) -> Objects.equals(mb.id, 321) && Objects.equals(mb.name, "321")))).thenReturn(321);
assertEquals(Integer.valueOf(123), myService.measure(new MyBean(123, "123")));
assertEquals(Integer.valueOf(321), myService.measure(new MyBean(321, "321")));
assertEquals(Integer.valueOf(0), myService.measure(new MyBean(777, "777")));
}
@Test
public void testThatPasses(){
doReturn(123).when(myService).measure(argThat((mb) -> Objects.equals(mb.id, 123) && Objects.equals(mb.name, "123")));
doReturn(321).when(myService).measure(argThat((mb) -> Objects.equals(mb.id, 321) && Objects.equals(mb.name, "321")));
assertEquals(Integer.valueOf(123), myService.measure(new MyBean(123, "123")));
assertEquals(Integer.valueOf(321), myService.measure(new MyBean(321, "321")));
assertEquals(Integer.valueOf(0), myService.measure(new MyBean(777, "777")));
}

Answer 2

好吧，我找到了使用when(mock.callMe(any(Arg.class), any(Arg.class))).thenAnswer(new Answer<Integer> { ...});解决方法