{"id":1140,"date":"2010-10-15T12:57:24","date_gmt":"2010-10-15T19:57:24","guid":{"rendered":"https:\/\/simpleprogrammer.com\/2010\/10\/15\/the-purpose-of-unit-testing\/"},"modified":"2017-08-07T19:42:30","modified_gmt":"2017-08-07T23:42:30","slug":"the-purpose-of-unit-testing","status":"publish","type":"post","link":"https:\/\/simpleprogrammer.com\/the-purpose-of-unit-testing\/","title":{"rendered":"The Purpose of Unit Testing"},"content":{"rendered":"

Before you start learning up any new skill or concept, I suggest you take a look at my course “10 Steps to Learn Anything Quickly”.<\/a><\/em>\\n\\nI was reminded yesterday that there are still many people out there who still don\u2019t really understand the purpose of unit testing.\\n\\nA funny shift happened in the last 5 or so years.\\n\\nAbout 5 years ago, when I would suggest TDD or just doing some unit testing when creating code, I would get horrible responses back.\u00a0 Many developers and managers didn\u2019t understand why unit testing was important and thought it was just extra work.\\n\\nMore recently when I have heard people talking about unit testing, almost everyone agrees unit testing is a good idea, but not because they understand why, but because it is now expected in the programming world.\\n\\nProgress without understanding is just moving forward in a random direction.\\n\\n\"purpose<\/a>\\n\\n<\/p>\n

Getting back to the basics<\/h2>\n

\\n\\nUnit testing isn\u2019t testing at all.\\n\\nUnit testing, especially test driven development, is a design or implementation activity, not a testing activity.\\n\\nYou get two primary benefits from unit testing, with a majority of the value going to the first:\\n\\n<\/p>\n

    \\n <\/p>\n
  1. Guides your design to be loosely coupled and well fleshed out.\u00a0 If doing test driven development, it limits the code you write to only what is needed and helps you to evolve that code in small steps.<\/li>\n

    \\n <\/p>\n

  2. Provides fast automated regression for refactors and small changes to the code.<\/li>\n

    \\n<\/ol>\n

    \\n\\nI\u2019m not saying that is all the value, but those are the two most important.\\n\\n(Unit testing also gives you living documentation about how small pieces of the system work.)\\n\\nUnit testing forces you to actually use the class you are creating and punishes you if the class is too big and contains more than one responsibility.<\/strong>\\n\\nBy that pain, you change your design to be more cohesive and loosely coupled.\\n\\nYou consider more scenarios your class could face and determine the behavior of those, which drives the design and completeness of your class.\\n\\nWhen you are done, you end up with some automated tests that do not ensure the system works correctly, but do ensure the functionality does not change.\\n\\nIn reality, the majority of the value is in the act of creating the unit tests when creating the code.\u00a0 This is one of the main reasons why it makes no sense to go back and write unit tests after the code has been written.\\n\\n<\/p>\n

    The flawed thinking<\/h2>\n

    \\n\\nHere are some bad no-nos that indicate you don\u2019t understand unit testing:\\n\\n<\/p>\n