Unit testing a function that (tries to) determine if an array is associative (php >= 7.3)

isAssociativeArrayTest.php

<?php

namespace Tests\Unit;

// based on original work from the PHP Laravel framework
if (!function_exists('str_contains')) 
{
    function str_contains($haystack, $needle) {
        return $needle !== '' && mb_strpos($haystack, $needle) !== false;
    }
}

// Matteo Galletti - https://www.php.net/manual/en/function.array-is-list
if (!function_exists('array_is_list'))
{
    function array_is_list(array $a) {
        return $a === [] || (array_keys($a) === range(0, count($a) - 1));
    }
}


use PHPUnit\Framework\TestCase;

/**
 * @version php@>=7.3
 */
class ArrayUtilTest extends TestCase
{

   /**
     * Check if an array is associative
     *
     * @link https://gist.github.com/Thinkscape/1965669#gistcomment-4029335 (method5,6) Benchmarks
     * @throws \JsonException array to json conversion problem
     */
    public static function isAssociative(array $arr): bool
    {
        // consider empty, and [0, 1, 2, ...] sequential
        if (empty($arr) || array_is_list($arr)) {
            return false;
        }

        // first scenario:
        // [  1  => [*any*] ]
        // [ 'a' => [*any*] ]
        foreach ( $arr as $key => $value ) {
            if (is_array($value)) {
                return true;
            }
        }

        // second scenario: read the json string
        $jsonNest = json_encode($arr, JSON_THROW_ON_ERROR);

        return str_contains($jsonNest, '{');
    }
    
    

    /**
     * Associative (true) expectation
     *
     * @throws \JsonException
     * @return void
     */
    public function testAssociativeArrayCases(): void
    {
        foreach ( $this->associativeValues() as $associativeArray ) {
            $this->assertTrue(
                ArrayUtil::isAssociative($associativeArray),
                ">> " . json_encode($associativeArray) . "\nwas not recognized as associative"
            );
        }
    }

    /**
     * Sequential (false) expectation
     *
     * @throws \JsonException
     * @return void
     */
    public function testSequentialArrayCases(): void
    {
        foreach ( $this->sequentialValues() as $seqArray ) {
            $this->assertFalse(
                ArrayUtil::isAssociative($seqArray),
                '>> ' . json_encode($seqArray) . "\nwas not recognized as sequential"
            );
        }
    }
    

    private function associativeValues(): array
    {
        $assocNum[1]          = 0;
        $assocNum[2]          = 1;
        $other[0]             = 'a';
        $other[2]             = 'b';
        $other[3]             = 'c';
        $another              = [ 'b' => 0, '1' => 1 ];
        $anotherOne           = [ '1' => 3, '2' => 4 ];
        $assocIntCharArr[3]   = [ 'a' ];
        $assocIntCharAssoc[4] = [ 'a' => 'b' ];

        return [
            [ 'a' => 'b' ],
            [ 'a' => 'a' ],
            [ 'a' => [] ],
            [ 'a' => 1 ],
            [ 'b' => 0 ],
            [ 'a' => [ 'a', 'b', 'c' ] ],
            [ 'a' => 1, 'b' => 2, 'c' => [ 1, 2, 3 ] ],
            [ 'a' => 1, 'b' => 2, 'c' => [ 0, 1, 2 ] ],
            [ 'a' => [ 1 ] ],
            [ 'b' => [ 0 ] ],
            $assocNum,
            $other,
            $another,
            $anotherOne,
            $assocIntCharArr,
            $assocIntCharAssoc,
        ];
    }
    

    private function sequentialValues(): array
    {
        return [
            [ 1, 2, 3 ],
            [ 0, 1, 2 ],
            [ 0, 0, 0 ],
            [ 1 ],
            [ 0 ],
            [ [ 10, 20, 30 ] ],
            [ [ [ 30, 40, 50 ] ] ]
        ];
    }
    
}