Drop support for MYSQL_TEST_EXPERIMENTAL (GH-15467)

This environment variable serves to hide (parts of) tests from general
execution, and as the test failures show when that environment variable
is set, apparently it serves to hide (parts of) test from being
executed at all, thus causing test rot.

To avoid this in the future, we drop `MYSQL_TEST_EXPERIMENTAL`, and fix
the failing tests, except for mysqli_get_warnings.phpt, which appears
to be broken beyond repair, and whose most important tests are already
covered by other test cases.

Co-authored-by: Kamil Tekiela <tekiela246@gmail.com>

Author: cmb69

ext/mysqli/tests/connect.inc

@@ -20,9 +20,6 @@
         ini_set('mysqli.default_socket', $socket);
     }
 
-    /* Development setting: test experimental features and/or feature requests that never worked before? */
-    $TEST_EXPERIMENTAL = 1 == getenv("MYSQL_TEST_EXPERIMENTAL");
-
     function get_environment_connection_flags(): int {
         static $connect_flags = null;
         if ($connect_flags === null) {

ext/mysqli/tests/mysqli_class_mysqli_result_interface.phpt

@@ -130,13 +130,10 @@ require_once 'skipifconnectfailure.inc';
         $mode = mt_rand(-1000, 1000);
     } while (in_array($mode, $valid));
 
-    if ($TEST_EXPERIMENTAL) {
-        ob_start();
+    try {
         new mysqli_result($link, $mode);
-        $content = ob_get_contents();
-        ob_end_clean();
-        if (!stristr($content, 'Invalid value for resultmode'))
-            printf("[009] Expecting warning because of invalid resultmode\n");
+    } catch (ValueError $ex) {
+        echo $ex->getMessage(), "\n";
     }
 
     print "done!";
@@ -169,4 +166,5 @@ mysqli_result->unknown = ''
 
 Constructor:
 mysqli_result object is already closed
+mysqli_result::__construct(): Argument #2 ($result_mode) must be either MYSQLI_STORE_RESULT or MYSQLI_USE_RESULT
 done!

ext/mysqli/tests/mysqli_get_warnings.phpt

@@ -5,8 +5,6 @@ mysqli
 --SKIPIF--
 <?php
 require_once 'skipifconnectfailure.inc';
-if (!$TEST_EXPERIMENTAL)
-    die("skip - experimental (= unsupported) feature");
 ?>
 --FILE--
 <?php
@@ -16,15 +14,18 @@ if (!$TEST_EXPERIMENTAL)
         printf("[001] Cannot connect to the server using host=%s, user=%s, passwd=***, dbname=%s, port=%s, socket=%s\n",
             $host, $user, $db, $port, $socket);
 
+    if (!mysqli_query($link, "SET sql_mode=''"))
+        printf("[002] Cannot set SQL-Mode, [%d] %s\n", mysqli_errno($mysql), mysqli_error($mysql));
+    
     if (!mysqli_query($link, "DROP TABLE IF EXISTS test"))
-        printf("[002] [%d] %s\n", mysqli_errno($link), mysqli_error($link));
-
-    if (!mysqli_query($link, "CREATE TABLE test (id SMALLINT)"))
         printf("[003] [%d] %s\n", mysqli_errno($link), mysqli_error($link));
 
-    if (!mysqli_query($link, "INSERT INTO test (id) VALUES (1000000)"))
+    if (!mysqli_query($link, "CREATE TABLE test (id SMALLINT NOT NULL)"))
         printf("[004] [%d] %s\n", mysqli_errno($link), mysqli_error($link));
 
+    if (!mysqli_query($link, "INSERT INTO test (id) VALUES (1), (NULL)"))
+        printf("[005] [%d] %s\n", mysqli_errno($link), mysqli_error($link));
+
     if (!is_object($warning = mysqli_get_warnings($link)) || 'mysqli_warning' != get_class($warning)) {
         printf("[006] Expecting object/mysqli_warning, got %s/%s\n", gettype($warning), (is_object($warning) ? var_export($warning, true) : $warning));
     }
@@ -37,4 +38,5 @@ if (!$TEST_EXPERIMENTAL)
 require_once 'clean_table.inc';
 ?>
 --EXPECTF--
-Fatal error: Trying to clone an uncloneable object of class mysqli_warning in %s on line %d
+Fatal error: Uncaught Error: Trying to clone an uncloneable object of class mysqli_warning in %s:%d
+Stack trace:%A

ext/mysqli/tests/mysqli_warning_unclonable.phpt

@@ -142,6 +142,4 @@ function setup_table_with_data_on_default_connection(string $table): mysqli {
     return $link;
 }
 
-/* Development setting: test experimental features and/or feature requests that never worked before? */
-//$TEST_EXPERIMENTAL = 1 == getenv("MYSQL_TEST_EXPERIMENTAL");
 //$engine    = getenv("MYSQL_TEST_ENGINE")   ?: "InnoDB";