AbstractPlatformTestCase::getGenerateForeignKeySql() is internal to the test and cannot return NULL

tests/Doctrine/Tests/DBAL/Platforms/AbstractMySQLPlatformTestCase.php

@@ -152,7 +152,7 @@ abstract class AbstractMySQLPlatformTestCase extends AbstractPlatformTestCase
         return 'CREATE UNIQUE INDEX index_name ON test (test, test2)';
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id)';
     }

tests/Doctrine/Tests/DBAL/Platforms/AbstractPlatformTestCase.php

@@ -250,7 +250,7 @@ abstract class AbstractPlatformTestCase extends DbalTestCase
         self::assertEquals($sql, $this->getGenerateForeignKeySql());
     }
 
-    abstract public function getGenerateForeignKeySql() : string;
+    abstract protected function getGenerateForeignKeySql() : string;
 
     public function testGeneratesConstraintCreationSql() : void
     {

tests/Doctrine/Tests/DBAL/Platforms/AbstractPostgreSqlPlatformTestCase.php

@@ -65,7 +65,7 @@ abstract class AbstractPostgreSqlPlatformTestCase extends AbstractPlatformTestCa
         return 'CREATE INDEX my_idx ON mytable (user_name, last_login)';
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id) NOT DEFERRABLE INITIALLY IMMEDIATE';
     }

tests/Doctrine/Tests/DBAL/Platforms/AbstractSQLServerPlatformTestCase.php

@@ -181,7 +181,7 @@ abstract class AbstractSQLServerPlatformTestCase extends AbstractPlatformTestCas
         return 'CREATE UNIQUE INDEX index_name ON test (test, test2) WHERE test IS NOT NULL AND test2 IS NOT NULL';
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id)';
     }

tests/Doctrine/Tests/DBAL/Platforms/DB2PlatformTest.php

@@ -42,7 +42,7 @@ class DB2PlatformTest extends AbstractPlatformTestCase
         ];
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id)';
     }

tests/Doctrine/Tests/DBAL/Platforms/OraclePlatformTest.php

@@ -234,7 +234,7 @@ class OraclePlatformTest extends AbstractPlatformTestCase
         return 'CREATE UNIQUE INDEX index_name ON test (test, test2)';
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id)';
     }

tests/Doctrine/Tests/DBAL/Platforms/SQLAnywherePlatformTest.php

@@ -43,7 +43,7 @@ class SQLAnywherePlatformTest extends AbstractPlatformTestCase
         ];
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
         return 'ALTER TABLE test ADD FOREIGN KEY (fk_name_id) REFERENCES other_table (id)';
     }

tests/Doctrine/Tests/DBAL/Platforms/SqlitePlatformTest.php

@@ -286,9 +286,9 @@ class SqlitePlatformTest extends AbstractPlatformTestCase
         parent::testGeneratesConstraintCreationSql();
     }
 
-    public function getGenerateForeignKeySql() : string
+    protected function getGenerateForeignKeySql() : string
     {
-        return null;
+        return '';
     }
 
     public function testModifyLimitQuery() : void