Documenting Go Code With Beautiful Tests - GopherCon UK 2018

Documenting Go Code  with  Beautiful Tests Paweł Słomka

@pawel_slomka ABOUT ME @pawel_slomka

@pawel_slomka ABOUT ME • Blogger at mycodesmells.com @pawel_slomka

@pawel_slomka ABOUT ME • Blogger at mycodesmells.com • Go developer
at Ingrid @pawel_slomka

at Ingrid • Co-organizer of GoWroc meetup @pawel_slomka

at Ingrid • Co-organizer of GoWroc meetup • Runner @pawel_slomka

at Ingrid • Co-organizer of GoWroc meetup • Runner • Millenial @pawel_slomka

at Ingrid • Co-organizer of GoWroc meetup • Runner • Millenial Alll GIFs by giphy.com @pawel_slomka

@pawel_slomka WHY DO WE WRITE TESTS

@pawel_slomka WHY WE WRITE THEM

@pawel_slomka WHY WE WRITE THEM 1 • Making sure code
works

works 2 • Improve maintainability (will work in the future)

works 2 • Improve maintainability (will work in the future) 3 • Document usage

@pawel_slomka WHY WE WRITE THEM NOW 1 2 3 FUTURE
YOU FUTURE THEM 1 • Making sure code works 2 • Improve maintainability (will work in the future) 3 • Document usage

@pawel_slomka “PRODUCTION” CODE vs TEST CODE

@pawel_slomka LIFE CYCLE OF  PRODUCTION CODE

@pawel_slomka LIFE CYCLE OF  PRODUCTION CODE WRITE (ﬁrst time)

@pawel_slomka LIFE CYCLE OF  PRODUCTION CODE READ WRITE (ﬁrst time)

@pawel_slomka LIFE CYCLE OF  PRODUCTION CODE REF ACTOR READ WRITE
(ﬁrst time)

@pawel_slomka LIFE CYCLE OF  TEST CODE

@pawel_slomka LIFE CYCLE OF  TEST CODE WRITE (ﬁrst time)

@pawel_slomka LIFE CYCLE OF  TEST CODE PASSING? WRITE (ﬁrst time)

@pawel_slomka LIFE CYCLE OF  TEST CODE FORGET PASSING? WRITE (ﬁrst
time)

@pawel_slomka LIFE CYCLE OF  TEST CODE WTF IS THAT? FORGET
PASSING? WRITE (ﬁrst time)

@pawel_slomka LIFE CYCLE OF  TEST CODE REWRITE ALL WTF IS
THAT? FORGET PASSING? WRITE (ﬁrst time)

@pawel_slomka TDD  ALIVE OR DEAD?

@pawel_slomka SCHRÖDINGER’S  TDD

@pawel_slomka TDD DEAD

@pawel_slomka TDD DEAD So much effort!

@pawel_slomka TDD DEAD So much effort! I want my code
to work on the ﬁrst take

@pawel_slomka TDD DEAD So much effort! I want my code
to work on the ﬁrst take Not enough time (just enough to make code work)

@pawel_slomka SIDE TRACK

@pawel_slomka SIDE TRACK Who needs to start their day with
a cup of coffee?

a cup of coffee? What happens when there’s no coffee in the ofﬁce in the morning?

a cup of coffee? What happens when there’s no coffee in the ofﬁce in the morning? Go DROP some production database, works even better

@pawel_slomka TDD ALIVE

@pawel_slomka TDD ALIVE Helps you write testable code

@pawel_slomka TDD ALIVE Helps you write testable code Makes you
think about code design

think about code design You are safe around TDD fanatics (they’re hidden everywhere!)

think about code design You are safe around TDD fanatics (they’re hidden everywhere!) Keep you focused, just write a test and take a break

@pawel_slomka WHY WE DON’T WRITE TESTS

@pawel_slomka WHY WE   DON’T WRITE THEM

@pawel_slomka WHY WE   DON’T WRITE THEM We are lazy
(I checked, it works)

(I checked, it works) Writing tests is hard (especially the ﬁrst ones)

(I checked, it works) Writing tests is hard (especially the ﬁrst ones) The client didn’t pay for them (really?)

@pawel_slomka BEAUTIFUL TESTS

@pawel_slomka BEAUTIFUL TESTS TEST REPORTS TEST BODY

@pawel_slomka • Readable output BEAUTIFUL TESTS TEST REPORTS TEST BODY

@pawel_slomka • Readable output • Just enough to debug what
went wrong BEAUTIFUL TESTS TEST REPORTS TEST BODY

went wrong • Feedback loop is fast BEAUTIFUL TESTS TEST REPORTS TEST BODY

went wrong • Feedback loop is fast BEAUTIFUL TESTS TEST REPORTS TEST BODY • Easy to read

went wrong • Feedback loop is fast BEAUTIFUL TESTS TEST REPORTS TEST BODY • Easy to read • Easy to extend

@pawel_slomka TEST

@pawel_slomka TEST REPORTS

@pawel_slomka DON’T USE “VERBOSE” • Sample test code:

@pawel_slomka DON’T USE “VERBOSE” • Without verbose, you see logs
only from failing tests:

@pawel_slomka DON’T USE “VERBOSE” • With, it shows logs from
all test cases… • Without verbose, you see logs only from failing tests:

@pawel_slomka CHECK FOR   RACE CONDITIONS • Always check if
you have race conditions • Sample, risky code:

@pawel_slomka CHECK FOR   RACE CONDITIONS • Without ﬂag you
might not notice anything…

@pawel_slomka CHECK FOR   RACE CONDITIONS • …but tests can
help here, too: • Without ﬂag you might not notice anything…

@pawel_slomka USE FLAGS   FOR “SLOW” TESTS • If some
of your tests are slow:

@pawel_slomka USE FLAGS   FOR “SLOW” TESTS • If some
of your tests are slow: • …hide them behind a ﬂag (supported by go test)

@pawel_slomka AVOID CACHING RESULTS OF INTEGRATION TESTS • Go caches
test results if code doesn’t change:

@pawel_slomka AVOID CACHING RESULTS OF INTEGRATION TESTS • Go caches
test results if code doesn’t change: • This won’t work for integration tests - you want to run them even if the test code didn’t change:

@pawel_slomka TEST BODY

@pawel_slomka SUBTESTS

@pawel_slomka TABLE TESTS

@pawel_slomka WRITING ASSERTIONS • Use a library • https://github.com/stretchr/testify •
https://github.com/matryer/is • Build your own, add context:

@pawel_slomka USE “GOLDEN FILES” • Testing file generation • Don’t
put expected output in test file • Create an actual file with expected output • Much easier to see what you want to see • Works as a documentation, too!

@pawel_slomka MOCKING

@pawel_slomka DUMMY MOCKS • Build dummy mocks, tell them what
they need to return per test case:

@pawel_slomka TOO SMART MOCKS

@pawel_slomka REQUEST AWARE MOCKS • Make mock remember the input
if you want to verify:

@pawel_slomka CHECK FUNCTIONS

@pawel_slomka CHECK FUNCTIONS • My favourite way of writing tests
• Easy to read, easy to extend • For a function: • Create a check function type:

@pawel_slomka CHECK FUNCTIONS • Create factories for checks for errors,
values, etc:

@pawel_slomka CHECK FUNCTIONS • Create factories for checks for errors,
values, etc: • Trick - shorthand function to use in table tests:

@pawel_slomka CHECK FUNCTIONS

@pawel_slomka SUMMARY

@pawel_slomka CALL TO ACTION

@pawel_slomka CALL TO ACTION • Write tests to save your
sleep

sleep • Write tests to save your free time

sleep • Write tests to save your free time • Write tests for those coming after you

@pawel_slomka THANK YOU!

Documenting Go Code With Beautiful Tests - Goph...

Documenting Go Code With Beautiful Tests - GopherCon UK 2018

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