What Hollywood Can Teach You About Writing Good Unit Tests

There’s a surprising number of parallels between a good unit test and a good movie. Learning to write good unit tests is important since good unit tests are proven to increase velocity, while bad unit tests can have a detrimental effect on velocity. So let’s break down some of the elements of a good movie, and what that can teach us about good unit tests.

• A good movie takes time to establish character and motivations — a good unit test has the important parts of the initial setup in the test itself, and not in the beforeEach.
• A good movie doesn’t spend unnecessary time before the action — a good unit test puts uninteresting setup into the beforeEach.
• A good movie shows characters undergoing meaningful change — a good unit test covers a meaningful state change.
• A good movie shows the protagonist triumphing — a good unit test uses asserts appropriately to demonstrate correctness of code.
• A good movie doesn’t try to develop too many characters (sorry Game of Thrones fans) — a good unit test covers a single state change.
• A good movie has a clear beginning, middle, and end — a good unit test has the same with the AAA pattern: Arrange, Act, Assert.
• A good movie has a single climax — a good unit test only tests a single state/state change
• A good movie doesn’t take too long to end (sorry Return of the King fans) — a good unit test has a single “logical” assert and not a long series of different asserts.
• A good movie is filmed with the audience in mind — a good unit test is written with readability in mind.
• A good movie is filmed because someone had a story they needed to tell — a good unit test is written because a piece of code truly needed to be tested, and not just because a developer was jumping through hoops, or trying to hit a coverage requirement.
• A good movie is easy to follow and doesn’t confuse the audience — a good unit test doesn’t make use of branching or looping logic.

Did I miss any other parallels between good movies and good unit tests?

Happy coding!

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