Unit Testing: What? Why? How?

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John Blackbourn WordPress core developer Working with WordPress for 10+ years Senior Engineer at Human Made @johnbillion

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Unit Testing: What? Why? How?

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You’re Going to L VE Unit Testing

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That’s Enough of That

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Unit Testing: What? Why? How?

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A unit test is a piece of code which exists only to verify expectations about the behaviour of another piece of code Veriﬁcation

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a.k.a. “Does my function do what I expect it to do?”

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A unit test operates in isolation in order to avoid external interference Isolated

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Tests typically run on the command line CLI

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Tests are highly efﬁcient because they're quickly repeatable Automated

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Crossing your ﬁngers and hoping… is not a unit test

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Unit Testing: What? Why? How?

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A unit test can cover many scenarios and never misses anything Accuracy

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Unit tests give you increased assurance that changes are less likely to cause breakage Assurance

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Unit tests give you conﬁdence to make changes Conﬁdence

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Unit tests help you write better code Smaller functions Separation of concerns Quality

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Unit tests can be liberating Clarity

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Unit Testing: What? Why? How?

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“But I know that false isn’t true”

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Arrange Act Assert AAA

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Each time a WordPress test runs, it operates on a fresh installation Remember

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Accuracy Assurance Conﬁdence Quality?… The Result

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Assertions assertTrue( $actual ) assertFalse( $actual ) assertEquals( $expected, $actual ) assertCount( $expected, $actual ) assertObjectHasAttribute( $key, $actual ) assertArrayHasKey( $key, $actual ) assertWPError( $actual ) assertCanonical( $actual, $expected )

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a.k.a. A Real World Gotcha Type Juggling Kills Me

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WUT

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Provide Veriﬁcation Isolated Automated Recap

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Accuracy Assurance Conﬁdence Quality Recap

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Arrange Act Assert Recap

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I Hope You’ll Fall In L VE With Testing

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Read the WordPress Unit Tests Visit PHPUnit website for reference Check out WP-CLI scaffolding What Next?

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John Blackbourn @johnbillion