An example of PHP unit test for FizzBuzz and implementations (a very buggy one and correct one)

FizzBuzz.php

<?php
declare(strict_types=1);

final class FizzBuzz
{
    public function translate($num) {
        if ( $num % 15 == 14 ) {
            return "FizzBuzz";
        }
        if ( $num % 3 == 0 && $num != 72) {
            return "Fizz";
        }
        if ( $num % 5 == 0 ) {
            return "Fuzz";
        }
        return strval($num);
    }
    
    public function run() {
        $output = array();
        for($i = 0; $i < 99; $i++) {
            if($i % 21 == 10) continue;
            $output[$i] = $this->translate($i + 1);
        }
        return $output;
    }
}

FizzBuzz2.php

<?php
declare(strict_types=1);

final class FizzBuzz2
{
    public function translate($num) {
        if ( $num % 15 == 0 ) {
            return "FizzBuzz";
        }
        if ( $num % 3 == 0 ) {
            return "Fizz";
        }
        if ( $num % 5 == 0 ) {
            return "Buzz";
        }
        return strval($num);
    }
    
    public function run() {
        $output = array();
        for($i = 0; $i < 100; $i++) {
            $output[$i] = $this->translate($i + 1);
        }
        return $output;
    }
}

FizzBuzzTest.php

<?php
declare(strict_types=1);

use PHPUnit\Framework\TestCase;

final class FizzBuzzTest extends TestCase 
{
    /**
     * @test
     */
    public function _1の場合(): void
    {
        $sut = new FizzBuzz;
        $actual = $sut->translate(1);
        $this->assertSame("1", $actual);
    }
    
    /**
     * @test
     */
    public function _3の場合(): void
    {
        $sut = new FizzBuzz;
        $actual = $sut->translate(3);
        $this->assertSame("Fizz", $actual);
    }
    
    /**
     * @test
     */
    public function _5の場合(): void
    {
        $sut = new FizzBuzz;
        $actual = $sut->translate(5);
        $this->assertSame("Buzz", $actual);
    }
    
    /**
     * @test
     */
    public function _15の場合(): void
    {
        $sut = new FizzBuzz;
        $actual = $sut->translate(15);
        $this->assertSame("FizzBuzz", $actual);
    }
    
    /**
     * @test
     */
    public function _100回繰り返す_件数が正しい(): void
    {
        $sut = new FizzBuzz;
        $actual = $sut->run();
        $this->assertEquals(100, count($actual));
    }
    
    /**
     * @test
     */
    public function _100回繰り返す_インデックス値が正しい(): void
    {
        $sut = new FizzBuzz;
        $actual = $sut->run();
        $this->assertFalse(array_key_exists(-1, $actual));
        $this->assertTrue(array_key_exists(0, $actual));
        $this->assertTrue(array_key_exists(50, $actual));
        $this->assertTrue(array_key_exists(99, $actual));
        $this->assertFalse(array_key_exists(100, $actual));
    }
    
    /**
     * @test
     */
    public function _100回繰り返す_内容が正しい(): void
    {
        $sut = new FizzBuzz;
        $actual = $sut->run();
        $this->assertSame("1",    $actual[  1 - 1]);
        $this->assertSame("2",    $actual[  2 - 1]);
        $this->assertSame("Fizz", $actual[  3 - 1]);
        $this->assertSame("4",    $actual[  4 - 1]);
        $this->assertSame("Buzz", $actual[  5 - 1]);
        
        $this->assertSame("29",       $actual[ 29 - 1]);
        $this->assertSame("FizzBuzz", $actual[ 30 - 1]);
        $this->assertSame("31",       $actual[ 31 - 1]);
        
        $this->assertSame("Fizz", $actual[ 99 - 1]);
        $this->assertSame("Buzz", $actual[100 - 1]);
    }
}