Sentence:  These are some common descriptions of badly constructed tests: Tests that sometimes run, sometimes fail (often this is caused by the use of threads, or <WSD>racy</WSD> code that relies on specific timing, by reliance on external dependencies, the order of tests being run in the test suite, or on shared state) 
Meaning of the word marked with <WSD> tags:  Involving a data race or a race condition.