Unable to mock URL class using PowerMockito/Mockito

Question

I am trying to use PowerMockito to mock the creation of the java.net.URL class in my code that I'm testing. Basically, I want to prevent the real HTTP request from occurring and instead 1) check the data when the request is made and 2) supply my own test data back on a mocked response. This is what I'm trying:

@RunWith(PowerMockRunner.class)
@PrepareForTest({ URL.class, MockedHttpConnection.class })
public class Test {
    URL mockedURL = PowerMockito.mock(URL.class);
    MockedHttpConnection mockedConnection = PowerMockito.mock(MockedHttpConnection.class);

...
    PowerMockito.whenNew(URL.class).withParameterTypes(String.class).withArguments("MyURLString").thenReturn(mockedURL);
PowerMockito.when(mockedURL.openConnection()).thenReturn(mockedConnection);

...
}

The code that I want to test looks like this:

URL wlInvokeUrl = new URL(wlInvokeUrlString);
connection = (HttpURLConnection) wlInvokeUrl.openConnection();

Earlier in my test scenario I mock the wlInvokeUrlString to match "MyURLString". I've also tried using various other forms of the whenNew line, trying to inject the mock. No matter what I try, it never intercepts the constructor. All I want to do is "catch" the call to openConnection() and have it return my mocked HTTP connection instead of the real one.

I have mocked other classes ahead of this one in the same script and these are working as expected. Either I need a second pair of eyes (probably true) or there is something unique about the URL class. I did notice that if I use "whenNew(URL.class).withAnyArguments()" and change the "thenReturn" to "thenAnswer" I could get it to trigger. Only problem is I never get the URL call for my code. What I see is an invocation of the 3-argument constructor for URL.class with all nulls for the parameters. Could it be this class is from the Java runtime and is bootstrapped by the test runner? Any help is much appreciated.

Answer 1

It's a common mistake when use PowerMockito.whenNew.

Note that you must prepare the class creating the new instance of MyClass for test, not the MyClass itself. E.g. if the class doing new MyClass() is called X then you'd have to do @PrepareForTest(X.class) in order for whenNew to work

From Powermock wiki

So, you need a bit change your test and add to @PrepareForTesta class which create a new instance of URLlike:

@RunWith(PowerMockRunner.class)
@PrepareForTest({ URL.class, MockedHttpConnection.class , ConnectionUser.class})
public class URLTest {
public class URLTest {

    private ConnectionUser connectionUser;

    @Before
    public void setUp() throws Exception {

        connectionUser = new ConnectionUser();
    }

    @Test
    public void testName() throws Exception {

        URL mockedURL = PowerMockito.mock(URL.class);
        MockedHttpConnection mockedConnection = PowerMockito.mock(MockedHttpConnection.class);

        PowerMockito.whenNew(URL.class).withParameterTypes(String.class).withArguments("MyURLString").thenReturn(mockedURL);
        PowerMockito.when(mockedURL.openConnection()).thenReturn(mockedConnection);

        connectionUser.open();

        assertEquals(mockedConnection, connectionUser.getConnection());


    }
}

where:

public class ConnectionUser {

    private String wlInvokeUrlString = "MyURLString";
    private HttpURLConnection connection;

    public void open() throws IOException {
        URL wlInvokeUrl = new URL(wlInvokeUrlString);
        connection = (HttpURLConnection) wlInvokeUrl.openConnection();
    }

    public HttpURLConnection getConnection() {
        return connection;
    }
}