Merge pull request rails#23751 from chezou/add-test-case-order-by-field

Add test cases about MySQL ORDER BY FIELD()

Author: pixeltrix

activerecord/test/cases/relations_test.rb

@@ -358,6 +358,12 @@ def test_finding_with_complex_order
   def test_finding_with_sanitized_order
     query = Tag.order(["field(id, ?)", [1,3,2]]).to_sql
     assert_match(/field\(id, 1,3,2\)/, query)
+
+    query = Tag.order(["field(id, ?)", []]).to_sql
+    assert_match(/field\(id, NULL\)/, query)
+
+    query = Tag.order(["field(id, ?)", nil]).to_sql
+    assert_match(/field\(id, NULL\)/, query)
   end
 
   def test_finding_with_order_limit_and_offset