Android Unit Testing with Robolectric

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Android unit testing with Robolectric Tho Nguyen Senior Android Developer @TradeHero

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How does Junit work

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Why Android is hard to do unit testing  Many of classes, methods are final  Lack of interfaces  Non public constructors  Static methods

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Have you tried?  Google does not want to show you the ugly part: Method bodies are replaced by a RuntimeException

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What have we tried?  No tests. God blesses us for almost half a year  Painful manual testing  Reproducing same bugs again and AGAIN  New developers join with risk  Integration testing  Slow  Not reliable  No fun  Robolectric  FuN~ 

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Robolectric  Tests run in JVM, not in DavikVM  No dexing, packaging, installation process. No emulator or device needed  Run on JVM  Fast  Freedom  Can use reflection without worry about performance  Can use big libraries, large jar file: apache common, google libraries like truth, guava.  Fast debugging and possible hot code swapping  Test behavior not implementation

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Robolectric

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How does Robolectric work  Shadow Objects  View and resources loading

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Shadow objects  Shadows back android classes. i.e ShadowImageView backs the ImageView class (Robolectric creates and uses shadow object instead of the real object if possible, look here)  Record state for testing verification  Simplify behaviors Shadow RealObject

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Custom shadow implementation

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Using custom shadow  Declaration  Usage

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View and resources loading  Robolectric parses layout files and build a tree of view objects with shadows  Robolectric also loads strings.xml, colors.xml …  Simulate runtime Android environment.

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Writing test  Specify that the test needs android instrument.

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Demo  Source code available at: https://github.com/nguyentruongtho/robomeetup  Writing Robolectric Junit test  Customize RobolectricTestRunner  TestLifecycleApplication  Robolectric & Dependency injection (Dagger)  Customize Robolectric for Maven, Git Submodule

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Question?  http://www.tradehero.mobi/Careers  Join us, boss robolectric will be watching you   Me  http://twitter.com/thontu  http://github.com/nguyentruongtho  http://linkedin.com/in/nguyentruongtho/  Resources  http://robolectric.org/  http://www.slideshare.net/tylerschultz/robolectric-android-unit- testing-framework