Mockito Programming Model: Difference between revisions
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===<tt>thenThrow()</tt>=== | ===<tt>thenThrow()</tt>=== | ||
<code>thenThrow(Throwable)</code> throws the given exception. This can be used together with JUnit feature that provides [[JUnit_Exception_Testing#.40Test_Annotation_.27expected.27_Attribute|syntactic support for tests that are supposed to check exceptions]] (<code>@Test(expected = | <code>thenThrow(Throwable)</code> throws the given exception. This can be used together with JUnit feature that provides [[JUnit_Exception_Testing#.40Test_Annotation_.27expected.27_Attribute|syntactic support for tests that are supposed to check exceptions]] (<code>@Test(expected = <exception-class>)</code>). | ||
===<tt>thenAnswer()</tt>=== | ===<tt>thenAnswer()</tt>=== |
Revision as of 17:08, 16 July 2021
Internal
Overview
API
import static org.mockito.Mockito.mock;
import com.example.ExternalDependency;
public class SomeClassTest {
private ExternalDependency mockExternalDependency;
@Before
public void setUp() {
mockExternalDependency = mock(ExternalDependency.class);
}
@Test
public void someTest() throws Exception {
...
}
}
Annotations
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;
import com.example.ExternalDependency;
public class SomeClassTest {
private AutoCloseable mocks;
@Mock
private ExternalDependency mockExternalDependency;
@Before
public void openMocks() {
mocks = MockitoAnnotations.openMocks(this);
}
@After
public void releaseMocks() throws Exception {
mocks.close();
}
@Test
public void someTest() throws Exception {
...
}
}
Implementing Stub Functionality
A stub returns synthetic responses or throws exceptions when its methods are invoked. Mockito supports stubbing and by returning a given value when a specific method of the managed test double is called. Mockito implements the stub functionality with Mockito.when(<method>).thenReturn(...)
pattern:
public class ExternalDependency {
public String someMethod() {
...
}
}
public class SomeClassTest {
@Mock
private ExternalDependency mockExternalDependency;
@Test
public void someTest() throws Exception {
Mockito.when(mockExternalDependency.someMethod()).thenReturn("some synthetic result");
...
}
}
The when()
configures the method(s) to stub, or the trigger action. The then*()
methods specify what to do when the trigger is activated. The options are:
Stub Responses
thenReturn()
thenReturn(...)
returns the given value. It has several variants:
thenReturn(value)
: return the same value every time.thenReturn(value1, value2, value3, ...)
: return the first value on first invocation, second value on the second invocation, etc. The equivalent is:thenReturn(value1).thenReturn(value2).thenReturn(value3). ...
thenThrow()
thenThrow(Throwable)
throws the given exception. This can be used together with JUnit feature that provides syntactic support for tests that are supposed to check exceptions (@Test(expected = <exception-class>)
).
thenAnswer()
thenAnswer(Answer answer)
: execute custom logic and compute a value to return. This turns the stub object into a fake.
thenCallRealMethod()
thenCallRealMethod()
. Delegates the invocation to the real external dependency.
Argument Matchers
isA()
public class ExternalDependency {
public String someMethodWithArg(String s) {
...
}
}
import static org.mockito.ArgumentMatchers.isA;
...
Mockito.when(mockExternalDependency.someMethodWithArg(isA(String.class))).thenReturn(...);
}
Why is isA() needed, why not provide the class, directly?