The Robert C. Martin Clean Code Collection (Collection) (Robert C. Martin Series)

by Robert C. Martin

Perhaps a better rule is that we want to test a single concept in each test function. We don’t want long test functions that go testing one miscellaneous thing after another. Listing 9-8 is an example of such a test. This test should be split up into three independent tests because it tests three independent things. Merging them all together into the same function forces the reader to figure out why each section is there and what is being tested by that section. Listing 9-8 /** * Miscellaneous tests for the addMonths() method. */ public void testAddMonths() { SerialDate d1 = SerialDate.createInstance(31, 5, 2004); SerialDate d2 = SerialDate.addMonths(1, d1); assertEquals(30, d2.getDayOfMonth()); assertEquals(6, d2.getMonth()); assertEquals(2004, d2.getYYYY()); SerialDate d3 = SerialDate.addMonths(2, d1); assertEquals(31, d3.getDayOfMonth()); assertEquals(7, d3.getMonth()); assertEquals(2004, d3.getYYYY()); SerialDate d4 = SerialDate.addMonths(1, SerialDate.addMonths(1, d1)); assertEquals(30, d4.getDayOfMonth()); assertEquals(7, d4.getMonth()); assertEquals(2004, d4.getYYYY()); } The three test functions probably ought to be like this: • Given the last day of a month with 31 days (like May): 1. When you add one month, such that the last day of that month is the 30th (like June), then the date should be the 30th of that month, not the 31st. 2. When you add two months to ...