BDD Mobilization

@eldudi Behavior Driven Development Paweł Dudek

@eldudi

@eldudi Behavior Driven Development Paweł Dudek

@eldudi What is a unit test? 5

@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.” 6

@eldudi Um… what? 7

@eldudi “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.” 8 Kolawa, Adam; Huizinga, Dorota (2007). Automated Defect Prevention: Best Practices in Software Management.

@eldudi What is an app? 9

@eldudi An app is a set of behaviours created by
programmer and expected by user. 10

@eldudi We, programmers, have a limited cognition. As all humans
do. 11

@eldudi We can’t always ‘load’ all of the code of
our app into our memory. 12

@eldudi This means that we can, by accident, change the
behaviour of the app. 13

@eldudi Preserving behaviour of complex systems is hard. In fact,
of any system at all. 14

@eldudi Enter unit tests. 15

@eldudi Unit test is a failsafe to make sure app
behaviour is preserved. 16

@eldudi They are a proof that all components in your
app behave as expected 17

@eldudi What is a usual approach to testing? 18

@eldudi Random Project Manager “Who needs units tests anyway?” 19

@eldudi Another Random Project Manager “Lets just write tests afterwards.”
20

@eldudi No test harness 21

@eldudi –Wikipedia “A safety harness is a form of protective
equipment designed to protect a person, animal, or object from injury or damage.” 22

@eldudi –Edsger W. Dijkstra “If one ﬁrst asks oneself what
the structure of a convincing proof would be and, having found this, then constructs a program satisfying this proof’s requirements, then these correctness concerns turn out to be a very effective heuristic guidance.” 23

@eldudi Write failing test 24

@eldudi Make it pass 25

@eldudi Red, Green 26

@eldudi Red, Green, Refactor 27

@eldudi TDD is born 28

@eldudi In TDD you always write test ﬁrst. Always. 29

@eldudi Which is then made green by writing/refactoring code 30

@eldudi TDD is not “just adding tests ﬁrst”. It’s a
complete workﬂow. 31

@eldudi TDD is a great way to determine how complex
your code has become. You just have to listen. 32

@eldudi Have to fake seven objects to isolate test? 33

@eldudi Have to inject a fake into a fake into
a fake? 34

@eldudi Your test setup method has 70 lines? 35

@eldudi This always points to an overcomplicated design And your
tests are here to point that out. Very clearly 36

@eldudi By writing test ﬁrst you’re becoming a consumer of
your upcoming API 37

@eldudi By writing the test ﬁrst, you're forced into thinking
what responsibilities given object should have. 38

@eldudi Let’s sidetrack a bit 39

@eldudi What should I test? 40

@eldudi How to explain what is being tested? 41

@eldudi How to clarify requirements? 42

@eldudi If you have questions like this - don’t worry.
You’re not alone.

@eldudi In fact, lots of people had this problems. And
they still have it. 44

@eldudi Best TDD practitioners already had an answer 45

@eldudi This is how BDD was created 46

@eldudi BDD is quite simple 47

@eldudi But it requires a shift in how you perceive
your test suite 48

@eldudi When writing tests don’t think ‘tests’ 49

@eldudi Think about ‘behaviours’ 50

@eldudi Think about examples how your object should behave 51

@eldudi An objects behaviour is deﬁned by methods it declares
in its interface 52

@eldudi You should not be testing internal implementation of your
object 53

@eldudi Work outside-in 54

@eldudi Use an ubiquitous language that helps understand what are
the requirements 55

@eldudi Example 56

@eldudi What unit tests can’t do? 57

@eldudi Unit tests are never a guarantee that you won’t
ship a bug. 58

@eldudi But they’re damn good at greatly reducing amount of
bugs. And time spent on QA. 59

@eldudi Quick recap 60

@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 61

@eldudi Beneﬁts? Robust codebase. Less bugs. More time for features!
62

@eldudi Go build great stuff! 63

@eldudi Thank you for your attention! 64

@eldudi Resources & Contact @eldudi github.com/paweldudek [email protected] Resources Contact objc.io/issue-15
65

@eldudi Lunch time! 66

BDD Mobilization

BDD Mobilization

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