Crafting Quality PHP Applications (PHP Joburg Oct 2019)

@asgrim
Crafting Quality PHP
Applications: an overview
James Titcumb
PHP Johannesburg Meetup - October 2019

$ whoami
James Titcumb
www.jamestitcumb.com
www.roave.com
@asgrim

@asgrim
What is “quality”?

@asgrim
photo: Rob Allen https://flic.kr/p/qmGpsq

@asgrim
"The best code is no code at all”
-- Jeff Atwood
source: https://blog.codinghorror.com/the-best-code-is-no-code-at-all/

@asgrim
Prototyping & short-lived apps/sites

@asgrim
Products
Long-lived projects. Open source software.

@asgrim
What is quality in applications?

@asgrim
What about time/cost…?

@asgrim
“A freelancer at $25 an hour for 100 hours still
costs more than a freelancer at $150 an hour that
takes 10 hours to do the same task”
-- Brandon Savage
source: http://www.brandonsavage.net/earning-more-money-as-a-php-freelancer/

@asgrim
This talk...
● Planning
● Development
● Testing
● Continuous integration
● Code reviews
● Deployments

@asgrim
Planning is communication

@asgrim
Use business terminology

@asgrim
Build a model of the business

@asgrim
The model must be fluid.

@asgrim
Feature Planning
Feature: Booking a room for a hotel
Scenario: Making a successful booking
Given there is a room available for £100 per night
When I select an available room for 3 nights
And I provide my payment details
Then I should see that my room has been reserved
And my card has been charged £300
Scenario: Cancelling an existing booking
Given I have an upcoming booking for 3 nights at £100 per night
When I choose to cancel the booking
Then I should see that the room is no longer reserved
And my card has been refunded £300

@asgrim
“There are only two hard things in Computer
Science: cache invalidation and naming things.”
-- Phil Karlton
source: https://martinfowler.com/bliki/TwoHardThings.html

@asgrim
SimpleBeanFactoryAwareAspectInstanceFactory

@asgrim
“Give awkward names to awkward concepts”
-- Eric Evans
source: https://skillsmatter.com/conferences/8231-ddd-exchange-2017

@asgrim
SOLID Violation Example
interface Thing {
public function doStuff() : void;
}
final class ImplementationOfThing implements Thing {
public function doStuff() : void { ... }
public function moreStuff() : void;
}
class ConsumerOfThing {
/** @var Thing */
private $thing;
public function woo() {
$this->thing->moreStuff();
}
}

@asgrim
Object Calisthenics
● One level of indentation in a method
● Avoid “else” keyword
● Wrap primitive types (e.g. strings, int)
● First class collections (instead of Thing[])
● One object operator (Law of Demeter)
● Avoid abbreviations (naming!)
● Keep classes small
● Avoid more than 2 instance variables
● No getters/setters

@asgrim
Avoid early abstraction

@asgrim
“Code for your use-case,
not for your re-use-case”
-- Marco Pivetta
source: https://ocramius.github.io/extremely-defensive-php/#/39

@asgrim
A public method is like a child:
once you've written it,
you are going to maintain it
for the rest of its life!
-- Stefan Priebsch

@asgrim
Strict type declarations.
Use declare(strict_types=1); by default

@asgrim
Immutable value objects
declare(strict_types=1);
use AssertAssertion; // beberlei/assert library !
final class PostalCode
{
private const VALIDATION_EXPRESSION = '(GIR 0AA)|((([A-Z-[QVX]][0-9][0-...
/** @var string */
private $value;
public function __construct(string $value) {
$this->assertValidPostalCode($value);
$this->value = $value;
}
private function assertValidPostalCode(string $value) : string {
Assertion::regex($value, self::VALIDATION_EXPRESSION);
}
public function __toString() : string {
return $this->value;
}
}

@asgrim
Value objects are valid!
declare(strict_types=1);
final class Thing {
public function assignPostalCode(PostalCode $postalCode) : void
{
// ... we can trust $postalCode is a valid postal code
}
}
// 12345 is not valid - EXCEPTION!
$myThing->assignPostalCode(new PostalCode('12345'));
// assignPostalCode is happy
$myThing->assignPostalCode(new PostalCode('PO1 1AA'));
// With STRICT types, this will also FAIL
$myThing->assignPostalCode(new PostalCode(12345));

@asgrim
Static Analysis
PhpStorm (+PHP Inspections EA)
Psalm
phpstan

@asgrim
Testing is NOT a separate line item

@asgrim
Testing should be an assumption

@asgrim
You’re already testing.

@asgrim
Still need convincing?

@asgrim
Reduce complexity
public function process(Stuff a, string b, int c) : MoreStuff
{
// lots of complicated code

@asgrim
Reduce complexity
public function meaningfulThing(Stuff a, string b, int c) : More
{
// call nicer, meaningful methods below
}
private function throwStuffIntoFire(Stuff a) : Fire
{
// smaller, meaningful chunk of code
}
private function combineStringWithFire(Fire a, string b) : string
{
// simple, lovely code!
}
private function postFlowersToSpain(int c) : void

@asgrim
More complexity = more tests

@asgrim
Line coverage
<?php
function foo(bool $a, bool $b) {
if ($a) {
echo "A";
}
if ($b) {
echo "B";
}
}
// generate coverage using calls:
foo(true, false);
foo(false, true);

@asgrim
Branch coverage
<?php
if ($a) {
echo "A";
}
if ($b) {
echo "B";
}
}
foo(true, false);
foo(false, true);

@asgrim
Branch coverage
<?php
if ($a) {
echo "A";
}
if ($b) {
echo "B";
}
}
foo(true, false);
foo(false, true);
foo(false, false); // NEW TEST!!!

@asgrim
Branch coverage
<?php
if ($a) {
echo "A";
}
if ($b) {
echo "B";
}
}
foo(true, false);
foo(false, true);
foo(false, false); // NEW TEST!!!
foo(true, true); // NEW TEST!!!

@asgrim
Prevent coverage leaking

@asgrim
Prevent coverage leaking
<?php
namespace Foo;
/**
* @covers FooBar
*/
final class BarTest extends TestCase
{
// write some tests!
}

@asgrim
Are the tests testing?

@asgrim
Example of a test not testing…
public function testPurchaseTickets()
{
$event = Event::create(uniq('event', true)
$customer = Customer::create(uniq('name', true));
$shop->purchaseTicket(1, $event, [$customer]);
}
@asgrim

@asgrim
Assert you’re asserting
public function testPurchaseTickets()
{
$event = Event::create(uniq('event', true)
$customer = Customer::create(uniq('name', true));
$receipt = $shop->purchaseTicket(1, $event, [$customer]);
self::assertSame($event, $receipt->event());
$customersInReceipt = $receipt->customers();
self::assertCount(1, $customersInReceipt);
self::assertContains($customer, $customersInReceipt);
}
@asgrim

@asgrim
Test the tests are testing!

@asgrim
Mutation testing
function add(int $a, int $b) : int {
return $a + $b;
}
function testAdd() {
$result = add(2, 3);
// self::assertSame(5, $result);
}

@asgrim
Mutation testing
return $a - $b;
}
// self::assertSame(5, $result);
}

@asgrim
Mutation testing
return $a - $b;
}
self::assertSame(5, $result);
// /// test will now fail with mutation
}

@asgrim
What about other tests?

@asgrim
BAD! Do not do this.
Feature: Ability to print my boarding pass
Scenario: A checked in passenger can print their boarding pass
Given I have a flight booked
And I have checked in
When I visit the home page
And I click the ".manage-booking" button
And I enter "CJM23L" in the ".bref-ipt-fld" field
And I click the "Find Booking" button
Then I should see the ".booking-ref.print" button
When I click the ".booking-ref.print" button
Then I should see the print dialogue

@asgrim
Better Behaviour test
Policies:
- Boarding passes are only available when already checked in
- If customer cannot print boarding pass, they can collect at
The airport
- more business rules etc...
Given I have a flight booked for LHR-MIA on 24th May
And I have previously checked in for the flight
When I display my booking reference "CJM23L"
Then I should be able to print my boarding pass
And the boarding pass should display flight details correctly

@asgrim
Why is this important?

@asgrim
Automated tests
Application (and UI, API, etc.)
Domain / Business Logic
Infrastructure (DBAL, APIs, etc.)

@asgrim
Testing at domain layer
Application (UI, API, etc.)
Domain / Business Logic
Infrastructure (DB, APIs, etc.)
// Testing via the UI
public function iDisplayMyBookingReference(string $reference)
{
$page = $this->getSession()->getPage();
$page->click(".manage-booking");
$page->findField(".bref-ipt-fld")->setValue($reference);
$page->click("Find Booking");
}
// Using the domain layer directly in tests
public function iDisplayMyBookingReference(string $reference)
{
$this->booking = $this->retrieveBooking($reference);
}

@asgrim
Some UI testing is okay!!!
Policies:
- Boarding passes are only available when already checked in
- If customer cannot print boarding pass, they can collect at
The airport
- more business rules etc...
@ui
Given I have a flight booked for LHR-OTP on 24th May
And I have previously checked in for the flight
When I display my booking reference "CJM23L"
Then I should be able to print my boarding pass
And the boarding pass should display flight details correctly

@asgrim
Automate all the things!

@asgrim
Continuous Integration

@asgrim
Tests cost money to run
(manually)

@asgrim
What to look for in code review?

@asgrim
Code style.

@asgrim
Small, atomic changes.

@asgrim
Composer versions.

@asgrim
Structure & good practices.

@asgrim
Tests.

@asgrim
Documentation.

@asgrim
Security.

@asgrim
Insight.

@asgrim
“Move fast and break things”
-- a stupid Facebook mantra

@asgrim
“Move fast and break things with stable infra”
-- Facebook mantra since 2014

@asgrim
Continuous Delivery & Deployment

@asgrim
Better quality = Higher confidence

@asgrim
Better quality = Higher confidence = Happy customers

Any questions?
James Titcumb
@asgrim

@asgrim
Resources
● Event Storming - Alberto Brandolini
○ http://ziobrando.blogspot.co.uk/2013/11/introducing-event-storming.html
● “Good Design is Imperfect Design” - Eric Evans
○ https://skillsmatter.com/skillscasts/9171-good-design-is-imperfect-design
● “Writing code that lasts” - Rafael Dohms
○ https://www.youtube.com/watch?v=I0y5jU61pS4
● Object Calisthenics - William Durand
○ https://williamdurand.fr/2013/06/03/object-calisthenics/
● “Driving Design through Examples” - Ciaran McNulty
○ https://www.youtube.com/watch?v=83GbyDpJDI4
● Code Review Checklist
○ https://asgrim.github.io/code-review-checklist/

Crafting Quality PHP Applications (PHP Joburg Oct 2019)

More Related Content

What's hot (20)

Similar to Crafting Quality PHP Applications (PHP Joburg Oct 2019) (20)

More from James Titcumb (17)

Recently uploaded (20)

Crafting Quality PHP Applications (PHP Joburg Oct 2019)