Repairing test dependence

In a test suite, all the tests should be independent: no test should affect another test's result, and running the tests in any order should yield the same test results. The assumption of such test independence is important so that tests behave consistently as designed. However, this critical assumption often does not hold in practice due to test dependence. Test dependence causes two serious problems: a dependent test may spuriously fail even when the software is correct (a false positive alarm), or it may spuriously pass even when a bug exists in the software (a false negative). Existing approaches to cope with test dependence require tests to be executed in a given order or for each test to be executed in a separate virtual machine. This paper presents an approach that can automatically repair test dependence so that each test in a suite yields the same result regardless of their execution order. At compile time, the approach refactors code under test and test code to eliminate test dependence and prevent spurious test successes or failures. We develop a prototype of our approach to handle one of the most common causes of test dependence and evaluate the prototype on five subject programs. In our experimental evaluation, our prototype is capable of eliminating up to 12.5% of the test dependence in the subject programs.