TDD isn't news, and most everyone agrees that writing tests (before, during or after implementation) is valuable. Hardly anyone agrees on what good, clean tests look like, though; if your tests are a live specification of your codebase, don't they deserve the same care and attention as your production code? This talk focuses on how to keep your tests readable, simple and maintainable. Specifically we'll discuss how the "given-when-then" pattern affects the way you factor your code, and showcase the remarkable differences between a sloppy specification and a well-factored one. Moderate experience with testing is expected; knowledge Scala might be helpful but is not required.

1. A quick guide to
Clean Tests
Noam Almog
Tech Lead
noam-almog
github.com/noam-almog
@NoamSon
noama@wix.com

2. “If you let the tests rot, then
your code will rot too”
Robert C. Martin

3. 01 / Guidelines

4. ● Readability, Readability, Readability !!!
● Maintainability
● Trustworthy
Tests Guidelines

5. ● Can it stand on it’s own ?
● Does is describe What and not How ?
● Does it express my intent ?
What is clean ?

6. 02 / Test Structure

7. public void testCancel_notDoneInterrupt() throws Exception {
Future<?> future = newFutureInstance();
assertTrue(future.cancel(true));
assertTrue(future.isCancelled());
assertTrue(future.isDone());
try {
future.get();
fail("Expected CancellationException");
} catch (CancellationException e) {
assertNotNull(e.getCause());
}
}
Given
When
Then

8. ● Init context
● Test Description
● Given - Setup test environment
● When - execute code
● Then - match expectations
Test Structure

9. 03 / Test Description

10. describe("Color Code Converter", function() {
describe("RGB to Hex conversion", function() {
it("converts the basic colors", function() {
….
});
});
@Test
void succeedingTest() {
...
}
"AppPublishRequestService" should {
"return publish request if request matcher publish request id" in new ctx {
...
}
Description
JavaScript - Mocha
Java - JUnit
Scala - Specs2

11. ● Use Neutral Language - English
Description
it("Given animal with black color will fail validation", function() {
…
});
“Given animal with black color will fail validation” in new ctx { ... }

12. ● Java Hint: camel case is less readable
Description
void givenAnimalWithBlackColorWillFailValidation()
void Given_animal_with_black_color_will_fail_validation()

13. ● Notice: It Does NOT compile !!!
Description
“Given animal with black color will fail validation” in new ctx {
validate(animal.copy(color = “Black”)) must beValid
}

14. 04 / Given

15. ● Describe What and not How
Given
cachePolicyAnnotationExtractor.cachePolicyFrom(method) returns None
def givenExtractorWithoutAnnotationFor(method: Method) { }

16. ● Reduce number of moving parts
Given
givenDaoWith(Seq(user1, user2, user3))
givenDaoWith(user1, user2, user3) // varargs
givenDaoWith(Some(name), description)
givenDaoWith(name, description) // useless wrappers

17. ● Don’t use concrete values if you don’t have to
Given
def givenUserWith("some@one.com", forUserId = 500) { ... }
def givenUserWith(email, forUserId = userId) { ... }

18. ● Introduce only needed data
Given
def givenSiteWith(url, name, andDescription = description, forSiteId = siteId)
siteChecker.siteFor(siteId).name must_=== name

19. Given
def givenPublishDaoWith(appPublishStatus.copy(landingPageUrl = None), appInstanceId)
def givenLandingPageServiceWith(landingPageUrl, forAppInstanceId = appInstanceId)
def givenDaoContainsPublishStatusWithoutLandingPageUrlFor(appInstanceId)
def givenLandingPageServiceWith(landingPageUrl, forAppInstanceId = appInstanceId)
● One api does not serve all

20. givenAppStateRouterWith(CreateStandalone, forAppInstanceId = appInstanceId)
givenMetaSiteWith2(webSiteUrl, forAppInstanceId = appInstanceId)
givenAppModelServiceWith(builderModel, forAppInstanceId = appInstanceId)
givenStandaloneRenderingServiceWith(screenshots, androidCoverName,
appPublishInformation.copy(icon = pmIconUrl), withBuilderModel = builderModel,
andAppInstanceId = appInstanceId, appModelVersion)
givenBuilderServiceWith(appPublishInformation, iconUrl = pmIconUrl,
forAppInstanceId = appInstanceId)
givenPublishedStatusServiceForNewStandaloneAppFor(appInstanceId)
Given - Pitfall Examples

21. 05 / When

22. ● Do NOT hide !
When
WixBiRecordingStudio.record {
logEvent() ←-- WHEN
} andThenPlay { recording =>
recording.play must contain(exactly(
aBiEventWithEntries("bar" -> "baz", "method" -> "foo")))
}

23. 06 / Then

24. ● Do NOT assert against anything you didn’t
define
Then
WixBiRecordingStudio.record {
logEvent()
} andThenPlay { recording =>
recording.play must contain(exactly(
aBiEventWithEntries("bar" -> "baz", "method" -> "foo")))
}

25. ● Describe what you are matching and not how
Then
person.age must be_>=(13)
person.age must be_<=(18)
person.location must_=== "USA"
person must beAmericanTeenager

26. ● Error message are important
Then

27. 07 / Initialize Context

28. ● Notice: Not visible for test reader
● Define only initialization code, cleanup etc.
● Hide only irrelevant logic
Context Initialization

29. 08 / Demo

30. "given no annotation return default cache headers" in new ctx {
cachePolicyAnnotationExtractor.cachePolicyFrom(method) returns None
cachePolicyManager.cachePolicyHeadersFor(method) must
containTheSameElementsAs(Seq("Cache-Control" -> "no-cache",
"Pragma" -> "no-cache"))
}
Demo - Before

31. "given no annotation return default cache headers" in new ctx {
givenExtractorWithoutCachePolicyFor(method)
cachePolicyManager.cachePolicyHeadersFor(method) must
containTheSameElementsAs(Seq("Cache-Control" -> "no-cache",
"Pragma" -> "no-cache"))
}
Demo - After 1

32. "given no annotation return default cache headers" in new ctx {
givenExtractorWithoutCachePolicyFor(method)
cachePolicyManager.cachePolicyHeadersFor(method) must
haveNoCacheControlHeaders
}
Demo - After 2

33. 09 / Conclusion

34. ● Test should stand on it’s own
● Reduce number of moving parts
● Don’t use anything you didn’t define
● Don’t define anything you won’t use
● Describe What and not How
● Use Neutral Language - English
Conclusion

35. This is where you are going to present your final words.
This slide is not meant to have a lot of text.Thank You!
Any Questions?
Noam Almog
noam-almog github.com/noam-
almog
@NoamSonnoama@wix.com