Getting MissingMethodInvocationException while testing with servlet and session

I'm trying to test my servlet to see if it calls my DAOService with some passed parameters from the session but running into this problem

The log:

org.mockito.exceptions.misusing.MissingMethodInvocationException: 
when() requires an argument which has to be 'a method call on a mock'.
For example:
    when(mock.getArticles()).thenReturn(articles);
at Servlet.SupplierServletTest.supplierServlet_StandardTest(SupplierServletTest.java:32)

The code

SupplierServlet supplierServlet = new SupplierServlet();
MockHttpServletRequest request = new MockMvcRequestBuilders.get("/SupplierServlet").buildRequest(new MockServletContext());
MockHttpServletResponse response = new MockHttpServletResponse();
MockHttpSession session = new MockHttpSession();

when(request.getSession()).thenReturn(session); //This is the line 32 that the log mentioned, I deleted the session part and the problem was the same for the following lines
when(request.getParameter("Name")).thenReturn("test"); 
when(request.getParameter("Address")).thenReturn("test");
when(request.getParameter("Phone")).thenReturn("1234");

supplierServlet.processRequest(request, response);
supplierDAO = mock(SupplierDAO.class);
verify(supplierDAO).newSupplier(new Supplier("test", "test", "1234"));

Any tip is appreciated

Solution

As for initialising MockHttpServletRequest, you should use the Spring provided builder. Since it is a class offered by the Spring framework (and is not a Mockito mock), using Mockito to mock its methods will result in an error.

MockHttpServletResponse response = new MockHttpServletResponse();
MockHttpSession session = new MockHttpSession();
MockHttpServletRequest request = MockMvcRequestBuilders.get("/SupplierServlet")
    .session(session)
    .param("Name", "test")
    .param("Address", "test")
    .param("Phone", "1234")
    .buildRequest(new MockServletContext());

supplierServlet.processRequest(request, response);
supplierDAO = mock(SupplierDAO.class);
verify(supplierDAO).newSupplier(new Supplier("test", "test", "1234"));

Moreover, your supplierDAO mock is useless. After mocking an object, you need to inject it into the code under test. It is usually done by passing the mock as a function parameter. Whereas in your test, you're trying to verify calls on a mock that was never used.