Add `foreign_key_exists?` method.

1 files changed, 21 insertions, 0 deletions

diff --git a/activerecord/test/cases/migration/foreign_key_test.rb b/activerecord/test/cases/migration/foreign_key_test.rb
index 78d9dd90a3..8cf2ead661 100644
--- a/activerecord/test/cases/migration/foreign_key_test.rb
+++ b/activerecord/test/cases/migration/foreign_key_test.rb
@@ -145,6 +145,27 @@ module ActiveRecord
         fk = foreign_keys.first
         assert_equal :nullify, fk.on_update
       end
+      
+      def test_foreign_key_exists
+        @connection.add_foreign_key :astronauts, :rockets
+
+        assert @connection.foreign_key_exists?(:astronauts, :rockets)
+        assert_not @connection.foreign_key_exists?(:astronauts, :stars)
+      end
+
+      def test_foreign_key_exists_by_column
+        @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id"
+        
+        assert @connection.foreign_key_exists?(:astronauts, column: "rocket_id")
+        assert_not @connection.foreign_key_exists?(:astronauts, column: "star_id")
+      end
+      
+      def test_foreign_key_exists_by_name
+        @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", name: "fancy_named_fk"
+        
+        assert @connection.foreign_key_exists?(:astronauts, name: "fancy_named_fk")
+        assert_not @connection.foreign_key_exists?(:astronauts, name: "other_fancy_named_fk")
+      end
 
       def test_remove_foreign_key_inferes_column
         @connection.add_foreign_key :astronauts, :rockets