如何为 Java 8 Predicate 编写 Mockito 测试

Question

我正在使用 Spring Boot REST 和 Mockito。如何编写测试用例？

错误：

java.lang.NullPointerException
    at java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1011)
    at java.util.concurrent.ConcurrentHashMap$KeySetView.add(ConcurrentHashMap.java:4595)
    at com.mastercard.customer.data.management.refdata.service.RegionService.lambda$2(RegionService.java:58)
    at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:174)
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    at java.util.stream.Streams$StreamBuilderImpl.forEachRemaining(Streams.java:419)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
    at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
    at com.mastercard.customer.data.management.refdata.service.RegionService.findAllRegions(RegionService.java:49)
    at com.mastercard.customer.data.management.refdata.service.RegionServiceTest.findAllRegions_SuccessTest(RegionServiceTest.java:68)
    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.mockito.internal.runners.DefaultInternalRunner$1$1.evaluate(DefaultInternalRunner.java:44)
    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:74)
    at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:80)
    at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:39)
    at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:538)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:760)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:460)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:206)

代码

public List<Employee> findAllEmployees() {
List<Object> obj = mongoTemplate.query(Department.class).distinct("employees").all();
List<Employee> employees = null;
if (!CollectionUtils.isEmpty(obj)) {
    employees = obj.stream().map(e -> (Employee) e).filter(distinctByKey(Employee::getEmployeeCd)).collect(Collectors.toList());
}
return employees;
}

public <T> Predicate<T> distinctByKey(Function<? super T, ?> keyExtractor) {
Set<Object> seen = ConcurrentHashMap.newKeySet();
return t -> seen.add(keyExtractor.apply(t));
}

测试用例

@Test
public void findEmp() {
    when(mongoTemplate.query(Department.class)).thenReturn(executableDepartment);
    when(mongoTemplate.query(Department.class).distinct("employees")).thenReturn(distinctDepartment);
    when(mongoTemplate.query(Department.class).distinct("employees").all()).thenReturn(obj);
    when(obj.stream()).thenReturn(Stream.of(obj));
    when(obj.stream().map(e -> (Region) e).thenReturn(Stream.of(region));

    assertNotNull(empService.findAllRegions());
}

Answer 1

1) 试着让你一个一个地模拟而不是级联调用：

when(mongoTemplate.query(Department.class)).thenReturn(executableDepartment);
when(executableDepartment).distinct("employees")).thenReturn(distinctDepartment);
when(distinctDepartment.all()).thenReturn(obj);

executableDepartment 和 distinctDepartment 当然也需要模拟。

2) 不要模拟 List 界面。向它提供预先配置的数据，并允许 SUT 按原样处理它。 sp mocking 应该只用在这部分：

mongoTemplate.query(Department.class).distinct("employees").all();

所以提供数据的部分。但是让实际的逻辑按原样运行。