1. <?php
2.  
3. namespace Tests\Unit;
4.  
5. use PHPUnit\Framework\TestCase;
6.  
7. class Calculator
8. {
9.     public static function add($a, $b)
10.     {
11.         return $a + $b;
12.     }
13.  
14.     public static function divide($a, $b)
15.     {
16.         return $a / $b;
17.     }
18. }
19.  
20. class CalculatorTest extends TestCase
21. {
22.     // Positive test case for add function
23.     public function testTwoPlusTwo(): void
24.     {
25.         $this->assertEquals(4, Calculator::add(2, 2));
26.     }
27.  
28.     // Positive test case for divide function
29.     public function testTwoDivideByTwo(): void
30.     {
31.         $this->assertEquals(1, Calculator::divide(2, 2));
32.     }
33.  
34.     // Negative test case for add function
35.     public function testTwoPlusOne(): void
36.     {
37.         $this->assertNotEquals(4, Calculator::add("a2a", "s1a"));
38.     }
39.  
40.     // Negative test case for divide function
41.     public function testOneDivideByZero(): void
42.     {
43.         $this->assertNotEquals(1, Calculator::divide(1, 0));
44.  
45.         // We cannot expect an exception for the case of 1/0 as the Calculator class does not throw an exception for this case, but instead returns infinity and issues a warning.
46.         // Therefore, we can use the below test case to check if the result of dividing by zero is finite or not.
47.         $this->assertFalse(is_finite(Calculator::divide(1, 0)));
48.     }
49. }
50.