Pragmatic Introduction to PHP Unit Testing (2015)

A Pragmatic Introduction
to (PHP) Unit Testing
Vienna PHP, March 2015
Peter Kofler, ‘Code Cop’
@codecopkofler
www.code-cop.org
Copyright Peter Kofler, licensed under CC-BY.

Peter Kofler
• Ph.D. (Appl. Math.)
• Professional Software
Developer for 15 years
• “fanatic about code quality”
• I help development teams
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

Yes, some but...
●
only what is already there
●
Trial & Error not popular in production
●
no practice - only production
●
time pressure

I help development teams with
●
Professionalism
●
Quality and
Productivity
●
Continuous
Improvement

Mentoring
●
Pair Programming
●
Programming
Workshops
●
Deliberate
Practice, e.g.
Coding Dojos

Developing Quality
Software Developers

Agenda
●
Unit Testing
●
PHPUnit
(Coding)
●
Break
●
PHPUnit
(Coding)
●
Retrospective

Quick Poll
●
Who has heard of PHPUnit? (xUnit)
●
Who has never written a unit test?
●
Who has written
a few?
●
Who writes unit
tests every day?
●
Who does TDD?

We Make Mistakes
●
at least I do... 
●
number of bugs proportional LoC
– 7 bugs per 1.000 LoC
– 1 bug per 10.000 LoC in critical software
●
Assume you have lots of bugs.

TESTING
I FIND YOUR LACK OF TESTS DISTURBING.

Unit Test (Micro Test)
●
code written by a developer
●
tests an individual unit
●
isolate each part
●
shows that the individual part is correct
●
sort of living documentation

Unit of Work
●
single logical functional use case
●
invoked by some public interface
– a single method,
– a whole class or
– multiple classes
●
with one single logical purpose

Test Class
●
unit test tests the functionality of a unit
●
for various inputs and outputs
●
usually a single test (class/script)
class FooTest extends
PHPUnit_Framework_TestCase
{ … }
contains all test cases for Foo

Test Methods
●
a test case tests the response of a single
method to a particular set of inputs
●
multiple test cases for a single method
●
test methods should be short, simple
●
tests without test methods are pointless
(public) function testMethod() {…}
/** @test */ function anyName() {…}

Only one aspect/feature
●
tests work best with lots of small tests
●
tests only fail because of one reason
●
more than 1 assert in test
split into multiple tests→
●
1 test case – 1 method – 1 assertion
testHighAndLowInput()
testHighInput()
testLowInput()

Assertions
●
no output from your tests!
●
check expectations programmatically
●
e.g. $this->assertEquals,
$this->assertTrue, …
●
test method without assert is pointless
●
one test method - one assertion
●
test runner reports failure on each test
 Regression Testing

Fixtures
●
sets up data needed to run tests
●
functions setUp(), tearDown()or
/** @before */, /** @after */
●
Test data is more likely to be wrong
than the tested code!

The Right BICEP
●
Right: Are the results right?
●
B: All the boundary conditions correct?
●
I: Can we check inverse relationships?
●
C: Can we cross-check results
using other means?
●
E: Can we force error conditions?
●
P: Are performance characteristics
within bounds?

“I write unit tests for one
reason: so my co-workers
don't f*** up my code.”
(David Angry)

Focus on Behaviour

e.g. requirements are behaviour

names from (problem) domain

full sentences
(long, descriptive test method names)

expected behaviour should

separation per business module

Consist of 3 Simple Steps
●
Prepare Input – Arrange
●
Call Method – Act
●
Check Output – Assert
●
Use in form of Given-When-Then
●
No conditional logic ( more test cases)→
●
No loops ( parametrized test)→
/** @dataProvider <static function> */

Be F.I.R.S.T
●
Fast
●
Isolated (data, sequence)
●
Repeatable
●
Self-verifying
●
Timely

Test Code Quality
must be equal
Prod. Code Quality

Try PHPUnit yourself

Coding Dojo Mindset
●
Safe place outside
work
●
We are here to learn
●
Need to slow down
●
Focus on doing it right
●
Collaborative Game

Assignment
●
Find a pair.
●
Get https://bitbucket.org/pkofler/phpunit-koans
●
Run phpunit – should see no tests
●
Go through the test code
●
assertions commented/ incomplete
●
uncomment the assertions
●
and complete them making tests pass

Closing Circle
●
What did you learn today?
●
What surprised you today?
●
What will you do
differently in the
future?

Peter Kofler
@codecopkofler
www.code-cop.org

CC Images
●
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