用于StreamSupport的Junit测试案例

Question

I am new to test cases I tried several ways to write test case for below piece of code but I never succeeded. How to write junit test case for below code using Powermockito?

StreamSupport.stream(irSet.spliterator(), false)
            .filter(iResultRow -> iResultRow !=null)
            .mapToInt(iResultRow ->{
                String event = iResultRow.get("STF_TY_GH");
                return StringUtils.isNotBlank(event) ? Integer.parseInt(event) : 1;
            }).findFirst().orElse(1);

Answer 1

While, using a descent amount of mocks you can mock every single call, let me suggest you an alternative approach.

So you have a stream produced out of some input set ( irSet ) variable. This stream makes "some" processing and returns an integer result.

So if you "imagine" Its a black box: a kind of function that looks like this:

int doSomething(Set<SomeRow> irSet) {
  ... your implementation is here...
}

In this case, you might want to test what it does by supplying the various input sets and expecting for some outputs. What if there are null -s in the input? Will it fail or filter out what's needed. What if the set is empty? What if there is SomeRow that really has STF_TY_GH data, what if the set doesn't have such a row?

Here is a test for example:

  @Test
  public void test_rows_with_null_are_processed_correctly() {

      // setup:
      Set<SomeRow> input = ...// prepare a set with null values

      // when:
      Integer actual = underTest.doSomething(input)

      // then:
      // verify this "actual" whether it should be 1 or something else 
  }  

All-in-all, use mocks only for interactions (with something you can't really instantiate like DB API/remote HTTP calls) or for something that is not related to the tested code and is used as a dependency the tested code interacts with. After all, the goal of unit tests is to test your code (the implementation of doSomething in this case and not to mock everything out).