Partial Mocking on HttpSession

Question

There is a servlet i want to test , servlet have session and puts "loginBean" (which contain logged in user related info) inside session , which i have mocked already and working fine , now IN GUI level , there are 2 tab , DetailSet1 , detailsSet2 , when u enter data of DetailSet1 , it get saved in session and also does some business logic , now it comes to DetailsSet2 , you already have DetailSet1 in session , so it got all it needs , data is saved in DB. Now it's obvious i have to mock HttpSession because i am running unit cases from outside the container , but data which gets stored is also in HttpSession , if i mock those as well , it defeats the purpose of testing. so my Question is , i need HttpSession object to return mocked data for what i have it mocked for and it is suppose to act like any normal HttpSession object for other cases. Like , if code does session.setAttribute("name","Vivek") , then session.getAttribute("name") should return "Vivek" after that , but in case of mocked object it return "NULL" why? because i haven't mocked behaviour for "getAttribute("name").

In simple word Partial mocking for HttpSession or Interfaces.

Answer 1

HttpSession is an interface, so you'll need to either write your own implementation of it, or mock it. I would recommend mocking it with Mockito, then stubbing getAttribute and setAttribute to delegate to a HashMap, or some other suitable structure.

So in your test class, you'll have fields for

• your mocked HttpSession,
• a real HashMap<String,Object>

and you'll use Answer<Object> objects for each of getAttribute and setAttribute. Each Answer will just delegate the call off to the HashMap.

You could set all this up either in a @Before method, or in a @Test method like this.

@Mock private HttpSession mockHttpSession;
Map<String,Object> attributes = new HashMap<String,Object>();

@Test
public void theTestMethod() {

    Mockito.doAnswer(new Answer<Object>(){
        @Override
        public Object answer(InvocationOnMock invocation) throws Throwable {
            String key = (String) invocation.getArguments()[0];
            return attributes.get(key);
        }
    }).when(mockHttpSession).getAttribute(anyString());

    Mockito.doAnswer(new Answer<Object>(){
        @Override
        public Object answer(InvocationOnMock invocation) throws Throwable {
            String key = (String) invocation.getArguments()[0];
            Object value = invocation.getArguments()[1];
            attributes.put(key, value);
            return null;
        }
    }).when(mockHttpSession).setAttribute(anyString(), any());

Answer 2

The Spring Testing framework includes MockHttpSession. It is available via Maven:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-test</artifactId>
    <version>4.0.1.RELEASE</version>
</dependency>