Unit Testing: Specific testing & Flow of Control

Question

I am quite new to unit testing and testing in general. I am developing with phpUnit, but as my question is more general / a design question, the actual environment shouldn't be of too much importance.

I assume, that it is a good practice, to write your testcases as specific as possible. For example (the later the better):

assertNotEmpty($myObject);              // myObject is not Null 
assertInternalType('array', $myObject); // myObject is an array
assertGreaterThan(0, count($myObject)); // myObject actually has entries

If that is correct, here is my question:

Is it a accepted practice to write some flow control inside a testcase, if the state of the object one is testing against depends on external sources (i.e. DB) - or even in general?

Like:

if (myObject !== null) {
    if (count(myObject) > 0) {
    // assert some Business Logic
    }
    else {
    // assert some different Business Logic  
    }
} 

Is this kind of flow control inside a testcase admissible or is a "code smell" and should be circumvented? If it is ok, are there any tips or practices, which should be kept in mind here?

Answer 1

Paul's answer addresses test method scope and assertions, but one thing your question's code implied is that you would test A if the returned object had value X but test B if it had value Y. In other words, your test would expect multiple values and test different things based on what it actually got.

In general, you will be a happier tester if each of your tests has a single, known, correct value. You achieve this by using fixed, known test data, often by setting it up inside the test itself. Here are three common paths:

• Fill a database with a set of fixed data used by all tests. This will evolve as you add more tests and functionality, and it can become cumbersome to keep it up-to-date as things move. If you have tests that modify the data, you either need to reset the data after each test or rollback the changes.
• Create a streamlined data set for each test. During setUp() the test drops and recreates the database using its specific data set. It can make writing tests easier initially, but you still must update the datasets as the objects evolve. This can also make running the tests take longer.
• Use mocks for your data access objects when not testing those DAOs directly. This allows you to specify in the test exactly what data should be returned and when. Since you're not testing the DAO code, it's okay to mock it out. This makes the tests run quickly and means you don't need to manage data sets. You still have to manage the mock data, however, and write the mocking code. There are many mocking frameworks depending on your preference, including PHPUnit's own built-in one.