Java测试框架Mockito的简明教程

repositories { jcenter() }
dependencies { testCompile "org.mockito:mockito-core:1.+" }

//Let's import Mockito statically so that the code looks clearer
import static org.mockito.Mockito.*;
//mock creation
List mockedList = mock(List.class);
//using mock object
mockedList.add("one");
mockedList.clear();
//verification
verify(mockedList).add("one");
verify(mockedList).clear();

//You can mock concrete classes, not just interfaces
LinkedList mockedList = mock(LinkedList.class);
//stubbing
when(mockedList.get(0)).thenReturn("first");
when(mockedList.get(1)).thenThrow(new RuntimeException());
//following prints "first"
System.out.println(mockedList.get(0));
//following throws runtime exception
System.out.println(mockedList.get(1));
//following prints "null" because get(999) was not stubbed
System.out.println(mockedList.get(999));
//Although it is possible to verify a stubbed invocation, usually it's just redundant
//If your code cares what get(0) returns, then something else breaks (often even before verify() gets executed).
//If your code doesn't care what get(0) returns, then it should not be stubbed. Not convinced? See here.
verify(mockedList).get(0);

//stubbing using built-in anyInt() argument matcher
when(mockedList.get(anyInt())).thenReturn("element");
//stubbing using custom matcher (let's say isValid() returns your own matcher implementation):
when(mockedList.contains(argThat(isValid()))).thenReturn("element");
//following prints "element"
System.out.println(mockedList.get(999));
//you can also verify using an argument matcher
verify(mockedList).get(anyInt());

verify(mock).someMethod(anyInt(), anyString(), eq("third argument"));
//above is correct - eq() is also an argument matcher
verify(mock).someMethod(anyInt(), anyString(), "third argument");
//above is incorrect - exception will be thrown because third argument is given without an argument matcher.

//using mock
mockedList.add("once");
mockedList.add("twice");
mockedList.add("twice");
mockedList.add("three times");
mockedList.add("three times");
mockedList.add("three times");
//following two verifications work exactly the same - times(1) is used by default
verify(mockedList).add("once");
verify(mockedList, times(1)).add("once");
//exact number of invocations verification
verify(mockedList, times(2)).add("twice");
verify(mockedList, times(3)).add("three times");
//verification using never(). never() is an alias to times(0)
verify(mockedList, never()).add("never happened");
//verification using atLeast()/atMost()
verify(mockedList, atLeastOnce()).add("three times");
verify(mockedList, atLeast(2)).add("five times");
verify(mockedList, atMost(5)).add("three times");

doThrow(new RuntimeException()).when(mockedList).clear();
//following throws RuntimeException:
mockedList.clear();

// A. Single mock whose methods must be invoked in a particular order
List singleMock = mock(List.class);
//using a single mock
singleMock.add("was added first");
singleMock.add("was added second");
//create an inOrder verifier for a single mock
InOrder inOrder = inOrder(singleMock);
//following will make sure that add is first called with "was added first, then with "was added second"
inOrder.verify(singleMock).add("was added first");
inOrder.verify(singleMock).add("was added second");
// B. Multiple mocks that must be used in a particular order
List firstMock = mock(List.class);
List secondMock = mock(List.class);
//using mocks
firstMock.add("was called first");
secondMock.add("was called second");
//create inOrder object passing any mocks that need to be verified in order
InOrder inOrder = inOrder(firstMock, secondMock);
//following will make sure that firstMock was called before secondMock
inOrder.verify(firstMock).add("was called first");
inOrder.verify(secondMock).add("was called second");
// Oh, and A + B can be mixed together at will

//using mocks - only mockOne is interacted
mockOne.add("one");
//ordinary verification
verify(mockOne).add("one");
//verify that method was never called on a mock
verify(mockOne, never()).add("two");
//verify that other mocks were not interacted
verifyZeroInteractions(mockTwo, mockThree);

//using mocks
mockedList.add("one");
mockedList.add("two");
verify(mockedList).add("one");
//following verification will fail
verifyNoMoreInteractions(mockedList);

public class ArticleManagerTest {
@Mock private ArticleCalculator calculator;
@Mock private ArticleDatabase database;
@Mock private UserProvider userProvider;
private ArticleManager manager;

when(mock.someMethod("some arg"))
.thenThrow(new RuntimeException())
.thenReturn("foo");
//First call: throws runtime exception:
mock.someMethod("some arg");
//Second call: prints "foo"
System.out.println(mock.someMethod("some arg"));
//Any consecutive call: prints "foo" as well (last stubbing wins).
System.out.println(mock.someMethod("some arg"));

when(mock.someMethod("some arg"))
.thenReturn("one", "two", "three");

when(mock.someMethod(anyString())).thenAnswer(new Answer() {
Object answer(InvocationOnMock invocation) {
Object[] args = invocation.getArguments();
Object mock = invocation.getMock();
return "called with arguments: " + args;
}
});
//the following prints "called with arguments: foo"
System.out.println(mock.someMethod("foo"));

doThrow(new RuntimeException()).when(mockedList).clear();
//following throws RuntimeException:
mockedList.clear();