I’m new in unit testing. For last two days I’m thinking how to test non-atomic methods with unit tests.
When i need to write tests for some simple, atomic method situation in pretty easy – i’m taking all scenarios for this method that i can imagine, and reforge each of it in unit test.

But what if i have methods that are calling other methods? Should I test each scenarios for tested method AND each methods it is calling?

Maybe some example will be easier to understand:

    public int makeSomeOperation(int a, int b)
    {
        if (a < 0)
            throw new ArgumentException("a must be greater that 0");
        if (b == 0)
            throw new ArgumentException("b cannot be 0");
        return a/b;
    }

    public bool SomeNonatomicMethod(int number)
    {
        if (number * number % 2 == 1)
            return false;
        int secondNumber = getNumberFromMordor();
        int result = makeSomeOperation(number, secondNumber);
        if (result == "123")
            return true;
        return false;
    }

In this case, makeSomeOperation is easy to test – one test for each exception, one to check in returning result is equals with expectations.

But what about SomeNonatomicMethod? Did I need to write not only test for each case in this method (so: power of number is odd, result is equal 123, and result is diffrent), but also each possible flow of things that may happen in getNumberFromMordor and makeSomeOperation?

Things that may happen in makeSomeOperation are already tested, so are they should be tested second time?