如何使用JUnit和Mockito模拟内部逻辑

Question

I'm kind of new to Junit and Mockito and trying to understand how to mock parts of logic of a class.

I have a method which does a http post and get call, but it might be a DB lookup. How do I mock the response from the HTTP call in this method

  BufferedReader in = new BufferedReader(new InputStreamReader(httpsConnection.getInputStream()));
String inputLine;
StringBuilder response = new StringBuilder();

while ((inputLine = in.readLine()) != null) {
    response.append(inputLine);
}

I mean there must a way to test my logic without doing to real http call or db lookup or whatever.

// HTTP GET request
public String sendGet(URL url) throws Exception {

    s_logger.debug("URL: " + url);
    HttpsURLConnection httpsConnection = (HttpsURLConnection) url.openConnection();

    // Add request header
    httpsConnection.setRequestMethod("GET");
    httpsConnection.setRequestProperty("Content-Type", "application/xml");

    if (sessionId != null) {
        httpsConnection.setRequestProperty("sessionId", sessionId);
    } else {
        httpsConnection.setRequestProperty("username", ACCOUNT_USERNAME);
        httpsConnection.setRequestProperty("password", ACCOUNT_PASSWORD);
    }

    httpsConnection.setInstanceFollowRedirects(false);
    httpsConnection.setUseCaches(false);

    // Print Request Header
    s_logger.debug("Request Header: " + httpsConnection.getRequestProperties());

    int responseCode = httpsConnection.getResponseCode();
    s_logger.debug("Response Code : " + responseCode);

    Map<String, List<String>> headerFields = httpsConnection.getHeaderFields();
    s_logger.debug("Response Header: " + headerFields);

    BufferedReader in = new BufferedReader(new InputStreamReader(httpsConnection.getInputStream()));
    String inputLine;
    StringBuilder response = new StringBuilder();

    while ((inputLine = in.readLine()) != null) {
        response.append(inputLine);
    }
    in.close();

    // Set Session ID
    final String SESSION_KEY = "sessionId";
    if (this.sessionId == null && httpsConnection.getHeaderFields().containsKey(SESSION_KEY)) {
        this.sessionId = httpsConnection.getHeaderFields().get(SESSION_KEY).get(0);
        s_logger.debug("SESSION ID : " + this.sessionId);
    }

    // print result
    s_logger.debug("RESPONSE: " + response.toString());
    return response.toString();
}

Thanks for any help or suggestion.

UPDATE: I did kind of that has been suggested but I'm not sure if this makes sense, also I don't like the fact that these methods are now public.

    final URL url = new URL("https://test.com");
    final String request = "Test";
    HttpsURLConnection httpsConnection = mock(HttpsURLConnection.class);


    final HttpConnectionClient httpSpy = spy(new HttpConnectionClient());
    Mockito.doReturn(httpsConnection).when(httpSpy).getConnection(url);
    Mockito.doNothing().when(httpSpy).sendRequest(httpsConnection, request);
    Mockito.doReturn(response).when(httpSpy).createBufferReader(httpsConnection);

    assertEquals(response,httpSpy.sendPost(url, request));

Answer 1

One hack is using spy and package-local methods:

public  class MyClass {
     public void myMethod() {
         //stuff
         stuffThatNeedsStubbing();
         //more stuff
     }

     void stuffThatNeedsStubbing() {
         //stuff that needs stub
     }
}

public class MyClassTest {
    @Test
    public void example() {
        final MyClass myClass = spy(new MyClass());
        doNothing().when(myClass).stuffThatNeedsStubbing();
        myClass.myMethod();
    }
}

In your case, you could create a package-local method BufferedReader createBufferedReader() , and replace this with a mock in your test.

Answer 2

The only tricky bit is the url.openConnection() because the URL is final class, so you cannot mock it. If you separate it, then you could use mock(HttpsURLConnection.class) using mockito and provide eg ByteArrayInputStream for the getInputStream() with mock-result.