Code Smell 82 - Tests Violating Encapsulation

Objects work fine and fulfill business objectives. But we need to test them. Let's break them.

TL;DR: Don't write methods with the only purpose of being used in your tests.

Problems

Encapsulation Violation.

Bad interfaces

Coupling

Solutions

Don't break encapsulation.

Test must be in full control.

If you cannot control your object, you are coupled. Decouple them!

Sample Code

Wrong

<?

class Hangman {
    private $wordToGuess;

    function __construct() {
        $this->wordToGuess = getRandomWord();
        //Test is not in control of this
    }

    public function getWordToGuess(): string {
        return $this->wordToGuess;
    }
}

class HangmanTest extends TestCase {
    function test01WordIsGuessed() {
        $hangmanGame = new Hangman();
        $this->assertEquals('tests', $hangmanGame->wordToGuess());
        //how can we make sure the word is guessed?
    }
}

Right

<?

class Hangman {
    private $wordToGuess;

    function __construct(WordRandomizer $wordRandomizer) {
        $this->wordToGuess = $wordRandomizer->newRandomWord();
    }
}

class MockRandomizer implements WordRandomizer {
    function newRandomWord(){
        return 'tests';
    }
}

class HangmanTest extends TestCase {
    function test01WordIsGuessed() {
        $hangmanGame = new Hangman(new MockRandomizer());
        $this->assertFalse($hangmanGame->wordWasGuessed());
        $hangmanGame->play('t');
        $this->assertFalse($hangmanGame->wordWasGuessed());
        $hangmanGame->play('e');
        $this->assertFalse($hangmanGame->wordWasGuessed());
        $hangmanGame->play('s');
        $this->assertTrue($hangmanGame->wordWasGuessed());
        //We just test behavior
    }
}

Detection

This is a design smell.

We can detect we need a method just for test.

Code Smell 52 - Fragile Tests

Maxi Contieri ・ Jan 4 ・ 2 min read

#codesmell #tutorial #codenewbie #webdev

Code Smell 28 - Setters

Maxi Contieri ・ Nov 19 '20 ・ 2 min read

#oop #codenewbie #programming #webdev

More Info

Should I Test Private Methods

Credits

This smell was inspired by @Rodrigo

Don't write methods with the only purpose of being used in your tests

Test the code how it must be used; the more real you can

In a hangman game, you don't expose a method to know the secret word. You test how the game behaves when you guess or miss letters

#cleanCode

12:00 PM - 24 Jun 2021