JMock makes it easy to mock up objects in unit tests.
Create Mock Objects
Use annotations @Rule and @Mock to create mock objects.
import org.jmock.auto.Mock;
import org.jmock.integration.junit4.JUnitRuleMockery;
import org.junit.Rule;
import org.junit.Test;
public class GettingStartedTest {
//The rule context field must be public
@Rule public final JUnitRuleMockery context = new JUnitRuleMockery();
@Mock private Runnable runnable;
@Test
public void testInvocation() {
...
}
}
Alternatively, you can define the mock object as follows:
Mockery context = new JUnit4Mockery();
private Runnable runnable = context.mock(Runnable.class);
Set Expectations on Invocations
@Test
public void testInvocation() {
// Set invocation expectations.
// You can use:
// oneOf, exactly(n).of,
// atLeast(n).of, atMost(n).of, between(min, max).of
// allowing, never
// For details, see http://www.jmock.org/cardinality.html
context.checking(new Expectations() {{
//The method runnable.run() will be invoked once and once only.
oneOf (runnable).run();
}});
runnable.run();
}
Mock (or Set Expectations on) Return Results
import static org.junit.Assert.*;
import java.util.Map;
import org.jmock.Expectations;
import org.jmock.auto.Mock;
import org.jmock.integration.junit4.JUnitRuleMockery;
import org.junit.Rule;
import org.junit.Test;
public class MockResultTest {
@Rule public final JUnitRuleMockery context = new JUnitRuleMockery();
@Mock private Map map;
@Test
public void testMockedResults() {
context.checking(new Expectations() {{
oneOf(map).get("Jason");
will(returnValue(10));
oneOf(map).get("Jay");
will(returnValue(5));
// You cannot define as follows:
// allowing(map).get("Jason"); ...
// allowing(map).get("Jay"); ...
// The 2nd allowing does not take effect.
allowing(map).remove(with(any(String.class)));
will(returnValue(100));
}});
assertEquals(map.get("Jason"), 10);
assertEquals(map.get("Jay"), 5);
assertEquals(map.remove("foo"), 100);
}
}
