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Unit Testing in Java

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Meet JUnit

2:56 with Craig Dennis

It's time to get familiar with JUnit the premier solution for unit testing in Java.

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    [MUSIC] 0:00
    Unit testing is popular in just about every programming language. 0:04
    We're going to be diving deep into the JUnit testing framework here. 0:08
    But you should know that just about all of the concepts 0:12
    are implemented in every other testing framework out there. 0:15
    There is a whole family of testing frameworks called the xUnit family. 0:19
    In fact, JUnit has been quite influential in the testing movement and 0:23
    has widespread acceptance. 0:27
    So, we're going to be working with a very well-loved, time-tested, mature, and 0:29
    ever-evolving framework. 0:34
    You'll see its influence in all the other frameworks, 0:36
    just like how all those bands from the 90s were pretty much just covering Pearl Jam. 0:39
    JUnit has evolved over time right along with Java. 0:44
    The way you actually write JUnit tests now is a little bit different than 0:47
    when the framework was first created in 1997. 0:51
    Now, the birth story of the xUnit family of frameworks is pretty great. 0:53
    Two developers, Kent Beck and Erich Gamma were headed to the same conference and 0:57
    sitting on a flight next to each other. 1:01
    And as coders do, 1:04
    they started talking about how there was no good framework for testing. 1:05
    So they built a test framework for Smalltalk. 1:09
    But get this, they did it using test-driven development. 1:11
    I don't know about you, but I would have loved to be the extra seat on that flight 1:15
    watching that metamagic happen. 1:18
    Today JUnit uses annotations to define tests. 1:21
    Obviously though, 1:24
    before the annotations were part of the language, this wasn't an option. 1:25
    The way they used to work was by following a naming convention of prefixing your text 1:29
    with the word test. 1:33
    This isn't the case anymore. 1:35
    And I'll show you the more newer accepted pattern. 1:37
    But again, as I pointed out in the past, 1:39
    there's a lot of dated information on the Internet. 1:41
    And some of these older patterns might make you think that you're required to do 1:44
    things this way. 1:48
    Some code completion tools, IntelliJ included, 1:49
    end up generating test methods following these outdated ways of writing tests, so 1:52
    it doesn't help to add to the confusion. 1:57
    As we explore, I'll do my best to call out the old way of doing things, 1:59
    and I'd like you to always remember to check the teachers notes. 2:03
    All right, so let's talk at a high level about what a testing framework gives you. 2:06
    This is what each individual test is called. 2:12
    Typically every class you end up attempting to test has many test cases. 2:15
    In JUnit, these are implemented as methods annotated with the @Test annotation. 2:19
    The methods return void and are grouped together under a parent class. 2:25
    That surrounding class around the test cases is known as a test fixture. 2:30
    It's responsible for setting things up that are needed for each test. 2:35
    A test runner finds and runs all the test cases that you specify. 2:39
    When it completes, it provides you with the results of how many tests passed and 2:44
    how many tests failed. 2:48
    So what do you say we get your test runner installed in IntelliJ? 2:49
    You'll be writing test fixtures jammed full of test cases in no time. 2:52

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