Merge d7c4b0c420 into 3eb61e353f

src/TestSessionEnvironment.php

@@ -625,9 +625,14 @@ class TestSessionEnvironment
 
     private function connectToDB(array $databaseConfig): void
     {
-        // Ensure we connect the primary connection and not a replica
-        // which can happen if we use the default value of DB::CONN_DYNAMIC
-        // and there is a replica database configured
-        DB::connect($databaseConfig, DB::CONN_PRIMARY);
+        if (method_exists(DB::class, 'hasConfig')) {
+            // CMS 5.4+ - ensure we connect the primary connection and not a replica
+            // which can happen if we use the default value of DB::CONN_DYNAMIC
+            // and there is a replica database configured
+            DB::connect($databaseConfig, DB::CONN_PRIMARY);
+        } else {
+            // CMS 5.3 and below do not support replica connections, use 'default' connection
+            DB::connect($databaseConfig);
+        }
     }
 }