Automatically skip ext/opcache tests under --preload

Also skip observer tests, as these will observe the additional
preload file inserted by the test runner.

Author: nikic

Diff for: run-tests.php

@@ -1326,14 +1326,24 @@ function system_with_timeout(
 function run_all_tests(array $test_files, array $env, $redir_tested = null): void
 {
     global $test_results, $failed_tests_file, $result_tests_file, $php, $test_idx, $file_cache;
+    global $preload;
     // Parallel testing
     global $PHP_FAILED_TESTS, $workers, $workerID, $workerSock;
 
-    if ($file_cache !== null) {
-        /* Automatically skip opcache tests in --file-cache mode,
-         * because opcache generally doesn't expect those to run under file cache */
-        $test_files = array_filter($test_files, function($test) {
-            return !is_string($test) || false === strpos($test, 'ext/opcache');
+    if ($file_cache !== null || $preload) {
+        /* Automatically skip opcache tests in --file-cache and --preload mode,
+         * because opcache generally expects these to run under a default configuration. */
+        $test_files = array_filter($test_files, function($test) use($preload) {
+            if (!is_string($test)) {
+                return true;
+            }
+            if (false !== strpos($test, 'ext/opcache')) {
+                return false;
+            }
+            if ($preload && false !== strpos($test, 'ext/zend_test/tests/observer')) {
+                return false;
+            }
+            return true;
         });
     }