✅ Add test for invalid mode via callable

Author: pboling

.rubocop_gradual.lock

@@ -21,11 +21,11 @@
   "lib/oauth2/response.rb:2054901929": [
     [53, 5, 204, "Style/ClassMethodsDefinitions: Use `class << self` to define a class method.", 996912427]
   ],
-  "spec/oauth2/access_token_spec.rb:373808463": [
+  "spec/oauth2/access_token_spec.rb:3464059918": [
     [3, 1, 34, "RSpec/SpecFilePathFormat: Spec path should end with `o_auth2/access_token*_spec.rb`.", 1972107547],
-    [809, 13, 25, "RSpec/ContextWording: Context description should match /^when\\b/, /^with\\b/, or /^without\\b/.", 770233088],
-    [879, 9, 101, "Style/ClassMethodsDefinitions: Use `class << self` to define a class method.", 3022740639],
-    [883, 9, 79, "Style/ClassMethodsDefinitions: Use `class << self` to define a class method.", 2507338967]
+    [824, 13, 25, "RSpec/ContextWording: Context description should match /^when\\b/, /^with\\b/, or /^without\\b/.", 770233088],
+    [894, 9, 101, "Style/ClassMethodsDefinitions: Use `class << self` to define a class method.", 3022740639],
+    [898, 9, 79, "Style/ClassMethodsDefinitions: Use `class << self` to define a class method.", 2507338967]
   ],
   "spec/oauth2/authenticator_spec.rb:853320290": [
     [3, 1, 36, "RSpec/SpecFilePathFormat: Spec path should end with `o_auth2/authenticator*_spec.rb`.", 819808017],

spec/oauth2/access_token_spec.rb

@@ -429,6 +429,21 @@ def assert_initialized_token(target)
             expect(subject.__send__(verb, "/token/#{mode.call(verb)}").body).to include(token)
           end
         end
+
+        context "when invalid" do
+          subject(:invalid_target) { target.__send__(http_verb, "/token/#{mode.call(http_verb)}") }
+
+          let(:http_verb) { :get }
+          let(:mode) do
+            lambda do |_verb|
+              "foobar"
+            end
+          end
+
+          it "correctly handles an invalid mode by raising an error" do
+            block_is_expected.to raise_error("invalid :mode option of foobar")
+          end
+        end
       end
 
       context "with client.options[:raise_errors] = false" do