title: Why should unit tests test only one thing?
body: <p><a href="/questions/61400/what-makes-a-good-unit-test">What Makes a Good Unit Test?</a> says that a test should test only one thing. What is the benefit from that?</p>
  
  <p>Wouldn't it be better to write a bit bigger tests that test bigger block of code? Investigating a test failure is anyway hard and I don't see help to it from smaller tests. </p>
  
  <p>Edit: The word unit is not that important. Let's say I consider the unit a bit bigger. That is not the issue here. The real question is why make a test or more for all methods as few tests that cover many methods is simpler.</p>
  
  <p>An example: A list class. Why should I make separate tests for addition and removal? A one test that first adds then removes sounds simpler.</p>