Mockito doReturn/when executes real method (without CGILIB)

Question

I have done many Mockito spy and just imitating my own working examples in a new project. But this failed miserably

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;
import org.testng.annotations.BeforeMethod;
import org.testng.annotations.Test;

import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import static org.mockito.Mockito.*;

public class SpyTest {
    HttpClient httpClient;
    private HttpResponse httpResponse;
    private StatusLine responseStatus;
    private HttpEntity responseEntity;

    @BeforeMethod
    public void setupClient() throws Exception {
        List spy = spy(new ArrayList());
        doReturn(true).when(spy).addAll(any(Collection.class)); // this works!

        DefaultHttpClient directClient = new DefaultHttpClient();
        httpClient = spy(directClient);
        httpResponse = mock(HttpResponse.class);
        responseStatus = mock(StatusLine.class);
        responseEntity = mock(HttpEntity.class);
        doReturn(responseStatus).when(httpResponse).getStatusLine();
        doReturn(responseEntity).when(httpResponse).getEntity();
        doReturn(httpResponse).when(httpClient).execute(any(HttpPost.class)); // failing here
    }

    @Test
    public void itShouldSetupTheSpy() throws Exception {
        doReturn(200).when(responseStatus).getStatusCode();
        doReturn("OK").when(responseStatus).getReasonPhrase();
        doAnswer(new Answer() {
            @Override
            public Object answer(InvocationOnMock invocation) throws Throwable {
                OutputStream os = (OutputStream) invocation.getArguments()[0];
                os.write("{\"id\": 100}".getBytes());
                return null;
            }
        }).when(responseEntity).writeTo(any(OutputStream.class));
    }
}

But I got error

java.lang.IllegalArgumentException: Request must not be null.
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:801)
    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:784)
    at SpyTest.setupClient(SpyTest.java:37)

I believe I have followed the official advice ! closely, like my other spies. And this answer ! does not seem to apply to me since I don't use CGLIB as evident from the maven dependency tree:

[INFO] +- org.codehaus.jackson:jackson-mapper-asl:jar:1.9.3:compile
    [INFO] |  \- org.codehaus.jackson:jackson-core-asl:jar:1.9.3:compile
    [INFO] +- org.testng:testng:jar:6.8:test
    [INFO] |  +- junit:junit:jar:4.10:test
    [INFO] |  |  \- org.hamcrest:hamcrest-core:jar:1.1:test
    [INFO] |  +- org.beanshell:bsh:jar:2.0b4:test
    [INFO] |  +- com.beust:jcommander:jar:1.27:test
    [INFO] |  \- org.yaml:snakeyaml:jar:1.6:test
    [INFO] +- org.mockito:mockito-all:jar:1.9.5:test
    [INFO] +- com.newrelic:newrelic-api:jar:2.3.0:compile
    [INFO] +- org.apache.httpcomponents:httpclient:jar:4.2.5:compile
    [INFO] |  +- org.apache.httpcomponents:httpcore:jar:4.2.4:compile
    [INFO] |  +- commons-logging:commons-logging:jar:1.1.1:compile
    [INFO] |  \- commons-codec:commons-codec:jar:1.6:compile
    [INFO] \- org.apache.commons:commons-lang3:jar:3.1:compile

It looks like having problem with the HttpClient and its subclasses.

Answer 1

execute is a final method , and Mockito can't mock final methods (as mentioned in the section on spying and also the FAQ ).

Why? Because you can't override final methods under normal circumstances, Java takes a shortcut and compiles calls (to final methods) directly to the implementations instead of looking them up in Java's equivalent of a virtual method table . This means that Mockito is never involved in final method calls, and therefore can't intercept behavior or even receive stubbing/verification calls.

Can you switch to mocking and using a raw HttpClient instead? You can mock any method of an interface without worrying about visibility or final method problems.