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.  
21. class CalculatorTest extends TestCase
22. {
23.     // Positive test case of add function
24.     public function testTwoPlusTwo(): void
25.     {
26.         $this->assertEquals(4, Calculator::add(2, 2));
27.     }
28.  
29.     // Positive test case of divide function
30.     public function testTwoDivideByTwo(): void
31.     {
32.         $this->assertEquals(1, Calculator::divide(2, 2));
33.     }
34.  
35.     // Negative test case of add function
36.     public function testTwoPlusOne(): void
37.     {
38.         $this->assertNotEquals(4, Calculator::add("a2a", "s1a"));
39.     }
40.  
41.     // Negative test case of divide function
42.     public function testOneDivideByZero(): void
43.     {
44.         $this->assertNotEquals(1, Calculator::divide(1, 0));
45.  
46.         // No need to expect exception (in case of 1/0) as Calculator class does not throw exception for this case and returns Infinity and issues warning.
47.  
48.         // Instead we can use below test case
49.         $this->assertFalse(is_finite(Calculator::divide(1, 0)));
50.     }
51. }
52.