How to get an actual code coverage report in IntelliJ IDEA?

Question

I have a simple class called SomeClass:

public class SomeClass {

    public int value = 0;

    public void inc() {
        value++;
    }

    public void dec()
    {
        if (isBiggerThanFive()) value--;
        value--;
    }

    private boolean isBiggerThanFive() {
        return value > 5;
    }
}

And a test class called TheTest:

class TheTest {

    SomeClass t;

    @BeforeEach
    void setUp() {
        t = new SomeClass();
    }

    @Test
    public void whenNewTestIsCreated_ValueIsZero()
    {
        assertEquals(t.value, 0);
    }

    @Test
    public void whenIncIsCalledWithValueOfZero_ValueIsOne()
    {
        t.inc();
        assertEquals(t.value, 1);
    }

    @Test
    public void whenDecIsCalledWithValueOfZero_ValueIsNegativeOne()
    {
        t.dec();
        assertEquals(t.value, -1);
    }
}

Note how the function dec is structured and how the whole if condition and the statement are on the same line. In the test, this part of decrementing by 2 when the value is bigger that 5 isn't tested. So I assume that I should see in the coverage report that this part is not covered. But that's what I get:

When instead I let the statment be on it's own line, I get the correct results:

Even though the code is completely the same, I get different results based on just the structure of the code. How can I have an indication that a part of a line isn't covered when it's not acutally covered?

Answer 1

IntelliJ's test coverage runner has different run settings (for performance reasons). By default, the Sampling mode is used. This results in a code line coverage with negligible (execution) slow-down. Now, if you'd like to have an accurate collection of the branch coverage (such as if-statements) then you can use the Trace mode. Using the Trace mode you'll get the following test coverage.

This is further documented on IntelliJ's help website. See Configure code coverage options.