Update mathcat_test.php

tests/mathcat_test.php

@@ -148,7 +148,7 @@ public static function conversion_of_array_to_vector_provider(): array {
             ],
 
             'modified and reordered' => [
-                'given' => [0, 'first' => 2, 'second' => [7, 9, 8], 'third' => 5],
+                'given' => [0, 'first' => 2, 'second' => [0 => 7, 2 => 8, 1 => 9], 'third' => 5],
                 'expected' => [0 => 0.0, 'first' => 2.0, 'second' => [0 => 7.0, 1 => 9.0, 2 => 8.0], 'third' => 5.0],
                 'structure' => [0 => 0, 'first' => 1, 'second' => [0 => 2, 1 => 3, 2 => 4], 'third' => 5],
             ],