Improves readability of escape sequences

tests/Doctrine/Tests/DBAL/Functional/Schema/MySqlSchemaManagerTest.php

@@ -451,13 +451,29 @@ class MySqlSchemaManagerTest extends SchemaManagerFunctionalTestCase
      * Ensure default values (un-)escaping is properly done by mysql platforms.
      * The test is voluntarily relying on schema introspection due to current
      * doctrine limitations. Once #2850 is landed, this test can be removed.
+     * @see https://dev.mysql.com/doc/refman/5.7/en/string-literals.html
      */
     public function testEnsureDefaultsAreUnescapedFromSchemaIntrospection() : void
     {
         $platform = $this->_sm->getDatabasePlatform();
         $this->_conn->query('DROP TABLE IF EXISTS test_column_defaults_with_create');
 
-        $default = "a\\0b\\'c\"d\te\\Zf\\\\g''h";
+        // https://dev.mysql.com/doc/refman/5.7/en/string-literals.html
+        $escapeSequences = [
+            "\\0",          // An ASCII NUL (X'00') character
+            "\\'", "''",    // Single quote
+            '\\"', '""',    // Double quote
+            '\\b',          // A backspace character
+            '\\n',          // A new-line character
+            '\\r',          // A carriage return character
+            '\\t',          // A tab character
+            '\\Z',          // ASCII 26 (Control+Z)
+            '\\\\',         // A backslash (\) character
+            '\\%',          // A percent (%) character
+            '\\_',          // An underscore (_) character
+        ];
+        $default = implode('+', $escapeSequences);
+
         $sql = "CREATE TABLE test_column_defaults_with_create(
                   col1 VARCHAR(255) NULL DEFAULT {$platform->quoteStringLiteral($default)} 
                )";