Implemented the Palindrome assessment including unit tests

Aurolieen/Palindrome.php

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+<?php
+
+namespace Aurolieen;
+
+/**
+ * Assessment 2. Palindrome
+ *
+ * Class Palindrome
+ * @package Aurolieen
+ */
+class Palindrome
+{
+    /**
+     * Checks whether or not the given word is a palindrome.
+     * One-letter or zero-letter strings are not considered palindromes by this algorithm.
+     *
+     * @param string $word The word to check.
+     * @return bool True if the word is a palindrome, false if otherwise.
+     */
+    public function isPalindrome($word)
+    {
+        if (!is_string($word)) return false;
+        $length = strlen($word);
+        if ($length <= 1) return false;
+        $characters = str_split($word);
+        $halfLength =  (int)($length / 2);
+        for ($i = 0; $i < $halfLength; $i++)
+        {
+            if (strcasecmp($characters[$i], $characters[$length - $i - 1]) !== 0) return false;
+        }
+        return true;
+    }
+}
+
+$palindrome = new Palindrome;
+echo $palindrome->isPalindrome('Deleveled');

Aurolieen/tests/PalindromeTest.php

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+<?php
+
+namespace Aurolieen\Tests;
+
+use Aurolieen\Palindrome;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Test suite for the Palindrome assessment class.
+ *
+ * Class PalindromeTest
+ * @package Aurolieen\Tests
+ */
+class PalindromeTest extends TestCase
+{
+    protected $palindrome;
+
+    /**
+     * Instantiates a Palindrome object on which the tests are executed.
+     */
+    public function setUp(): void
+    {
+        $this->palindrome = new Palindrome();
+    }
+
+    /**
+     * Tests that a word with an even amount of letters that is a palindrome results in true.
+     */
+    public function testEvenPalindrome()
+    {
+        $this->assertTrue($this->palindrome->isPalindrome('tattarrattat'), 'tattarrattat is a palindrome');
+        $this->assertTrue($this->palindrome->isPalindrome('doggod'), 'doggod is a palindrome');
+    }
+
+    /**
+     * Tests that a word with an odd amount of letters that is a palindrome results in true.
+     */
+    public function testOddPalindrome()
+    {
+        $this->assertTrue($this->palindrome->isPalindrome('deleveled'), 'deleveled is a palindrome');
+        $this->assertTrue($this->palindrome->isPalindrome('racecar'), 'racecar is a palindrome');
+    }
+
+    /**
+     * Tests that a word that isn't a palindrome, results in false.
+     */
+    public function testNonPalindrome()
+    {
+        $this->assertFalse($this->palindrome->isPalindrome('abc'), 'abc is not a palindrome');
+        $this->assertFalse($this->palindrome->isPalindrome('delevueled'), 'delevueled is not a palindrome');
+    }
+
+    /**
+     * Tests that differences in casing doesn't reflect the outcome of the result.
+     */
+    public function testCasingInvariance()
+    {
+        $this->assertEquals($this->palindrome->isPalindrome('DELEVeled'),
+            $this->palindrome->isPalindrome('delevELED'));
+    }
+
+    /**
+     * Tests that several input values that are invalid return false as output.
+     *
+     * @param mixed $input Invalid input.
+     * @dataProvider invalidInputProvider
+     */
+    public function testInvalidInput($input)
+    {
+        $this->assertFalse($this->palindrome->isPalindrome($input));
+    }
+
+    /**
+     * Provides invalid input data.
+     *
+     * @return array Array of arrays containing invalid input parameters.
+     */
+    public function invalidInputProvider()
+    {
+        return [
+            [null],
+            [''],
+            ['a']
+        ];
+    }
+}