[FIXED] JMockit Mock an object inside while loop

Issue

I have a below test class method that I am writing a test for.

  public String doSomething(Dependency dep) {
    StringBuilder content = new StringBuilder();
    String response;
    while ((response = dep.get()) != null) {
      content.append(response);
    }
    return content.toString();
  }

Below is the test case I have. Basically I want the Dependency#get() method to return "content" in the first iteration and null in the second.

  @Test
  void test(@Mocked Dependency dep) {
    new Expectations() {
      {
        dep.get();
        result = "content";
        times = 1;
      }
    };
    Assertions.assertEquals("content", testSubject.doSomething(dep));
  }

However this results in JMockit throwing Unexpected invocation to: Dependency#get() error. If I remove the times field, my test runs in a forever loop.

How can I test this method?

Solution

So I found out that JMockit apart from the result paramater can also set a returns(args...) method to which we can pass a series of arguments that it will expect sequentially. So modifying the test to this worked for me.

  @Test
  void test(@Mocked Dependency dep) {
    new Expectations() {
      {
        dep.get();
        returns("content", null);
        times = 2;   // limiting to mock only twice as only 2 values are provided in returns
      }
    };
    Assertions.assertEquals("content", testSubject.doSomething(dep));
  }

Answered By - shan-96
Answer Checked By - Senaida (JavaFixing Volunteer)