1 files changed, 18 insertions, 0 deletions
diff --git a/activesupport/test/core_ext/string_ext_test.rb b/activesupport/test/core_ext/string_ext_test.rb
index a26473dc84..1febb6a775 100644
--- a/activesupport/test/core_ext/string_ext_test.rb
+++ b/activesupport/test/core_ext/string_ext_test.rb
@@ -469,6 +469,15 @@ class StringAccessTest < ActiveSupport::TestCase
     assert_not_same different_string, string
   end
 
+  test "#first with negative Integer is deprecated" do
+    string = "hello"
+    message = "Calling String#first with a negative integer limit " \
+              "will raise an ArgumentError in Rails 6.1."
+    assert_deprecated(message) do
+      string.first(-1)
+    end
+  end
+
   test "#last returns the last character" do
     assert_equal "o", "hello".last
     assert_equal "x", "x".last
@@ -487,6 +496,15 @@ class StringAccessTest < ActiveSupport::TestCase
     assert_not_same different_string, string
   end
 
+  test "#last with negative Integer is deprecated" do
+    string = "hello"
+    message = "Calling String#last with a negative integer limit " \
+              "will raise an ArgumentError in Rails 6.1."
+    assert_deprecated(message) do
+      string.last(-1)
+    end
+  end
+
   test "access returns a real string" do
     hash = {}
     hash["h"] = true