add some behavioral tests

Author: LamentXU123

ext/standard/tests/array/sort/sort_single_element.phpt

@@ -0,0 +1,57 @@
+--TEST--
+Sorting single-element arrays does not invoke the comparison function
+--FILE--
+<?php
+
+$calls = 0;
+$compare = static function ($a, $b) use (&$calls) {
+    $calls++;
+    return $a <=> $b;
+};
+
+$array = [42];
+// Keep the array packed and without holes, but leave the next free index at 11.
+$array[10] = 99;
+unset($array[10]);
+next($array);
+var_dump(usort($array, $compare));
+var_dump($array, key($array));
+$array[] = 43;
+var_dump($array);
+
+$array = ['answer' => 42];
+next($array);
+var_dump(usort($array, $compare));
+var_dump($array, key($array));
+$array[] = 43;
+var_dump($array);
+
+var_dump($calls);
+
+?>
+--EXPECT--
+bool(true)
+array(1) {
+  [0]=>
+  int(42)
+}
+int(0)
+array(2) {
+  [0]=>
+  int(42)
+  [1]=>
+  int(43)
+}
+bool(true)
+array(1) {
+  [0]=>
+  int(42)
+}
+int(0)
+array(2) {
+  [0]=>
+  int(42)
+  [1]=>
+  int(43)
+}
+int(0)