40. (with egg)

Right after I posted Unit Testing: Leave No Trace vs. Schmutz, our team went to the opposite extreme regarding test data: we decided to load all test data (that is, all fixtures) before each test method executed. This took advantage of Rails fixture "feature" of deleting all data from the target fixture's table prior to that fixture's data being loaded into the table. Using this technique, we include all fixtures, thus deleting all Schmutz in the database prior to each test run.

At first, I was against this due to my Leave No Trace Rules philosophy, but then I started thinking about what we, as developers are guaranteeing to the tests, what the "contract" is for them... what is The Promise. I realized that The Promise is not strictly that we will start them with a clean database, but that we will start them from a known starting point. Based on that, deleting-then-loading all data is not really so different from starting from a clean database, because all tests start from the same known state.