Behaviour Driven Development - Mobile Trends

@eldudi Behavior Driven Development Paweł Dudek

@eldudi What is a unit test? 4

@eldudi Kolawa, Adam; Huizinga, Dorota (2007). Automated Defect Prevention: Best
Practices in Software Management. “Unit testing is a method by which individual units of source code, sets of one or more computer program modules together with associated control data, usage procedures, and operating procedures are tested to determine if they are ﬁt for use.” 5

@eldudi What is an app? 6

@eldudi An app is a set of behaviours created by
programmer and expected by user. 7

@eldudi We, programmers, have a limited cognition. As all humans
do. 8

@eldudi We can’t always ‘load’ all of the code of
our app into our memory. 9

@eldudi This means that we can, by accident, change the
behaviour of the app. 10

@eldudi Preserving behaviour of complex systems is hard. In fact,
of any system at all. 11

@eldudi Enter unit tests. 12

@eldudi Unit test is a failsafe to make sure app
behaviour is preserved. 13

@eldudi TDD 14

@eldudi In TDD you always write test ﬁrst. Always. 15

@eldudi Which is then made green by writing/refactoring code 16

@eldudi TDD is not “just adding tests ﬁrst”. It’s a
complete workﬂow. 17

@eldudi TDD is a great way to determine how complex
your code has become. You just have to listen. 18

@eldudi Have to fake seven objects to isolate test? 19

@eldudi Have to inject a fake into a fake into
a fake? 20

@eldudi Your test setup method has 70 lines? 21

@eldudi You need to simulate ﬁve events to test one
method? 22

@eldudi This always points to an overcomplicated design And your
tests are here to point that out. Very clearly 23

@eldudi By writing the test ﬁrst, you're forced into thinking
what responsibilities given object should have. 24

@eldudi By writing test ﬁrst you’re becoming a consumer of
your upcoming API 25

@eldudi SOLID 26

@eldudi BDD 27

@eldudi What should I test? 28

@eldudi If you asked this question - don’t worry. You’re
not alone.

@eldudi BDD is quite simple 30

@eldudi But it requires a shift in how you perceive
your test suite 31

@eldudi When writing tests don’t think ‘tests’ 32

@eldudi Think about ‘behaviors’ 33

@eldudi Think about examples how your object should behave 34

@eldudi An objects behavior is deﬁned by methods it declares
in its interface 35

@eldudi You should not be testing internal implementation of your
object 36

@eldudi Work outside-in 37

@eldudi Use examples to clarify requirements 38

@eldudi Use an ubiquitous language that helps understand what are
the requirements 39

@eldudi Example 40

@eldudi Recap 41

@eldudi BDD • Think examples/behaviors, not tests • Provide examples
how your object should behave • Don’t test implementation, work outside-in • Use ubiquitous language to make examples easily understandable 42

@eldudi Resources & Contact @eldudi github.com/paweldudek [email protected] Resources Contact objc.io/issue-15
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Behaviour Driven Development - Mobile Trends

Behaviour Driven Development - Mobile Trends

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