test: verify get_me succeeds with omitted tool arguments

Add an integration test that exercises the full get_me handler path when
clients omit the arguments field, matching the failure mode in #2587.

Author: root

pkg/github/context_tools_test.go

@@ -139,6 +139,47 @@ func Test_GetMe(t *testing.T) {
 	}
 }
 
+func Test_GetMe_OmittedArguments(t *testing.T) {
+	t.Parallel()
+
+	serverTool := GetMe(translations.NullTranslationHelper)
+
+	mockUser := &github.User{
+		Login:     github.Ptr("testuser"),
+		Name:      github.Ptr("Test User"),
+		HTMLURL:   github.Ptr("https://github.com/testuser"),
+		CreatedAt: &github.Timestamp{Time: time.Now()},
+	}
+	mockedClient := MockHTTPClientWithHandlers(map[string]http.HandlerFunc{
+		GetUser: mockResponse(t, http.StatusOK, mockUser),
+	})
+	deps := BaseDeps{Client: mustNewGHClient(t, mockedClient), Obsv: stubExporters()}
+	handler := serverTool.Handler(deps)
+
+	tests := []struct {
+		name      string
+		arguments json.RawMessage
+	}{
+		{name: "nil arguments", arguments: nil},
+		{name: "empty byte slice", arguments: json.RawMessage{}},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			request := createMCPRequestWithRawArguments(tc.arguments)
+			result, err := handler(ContextWithDeps(context.Background(), deps), &request)
+			require.NoError(t, err)
+			require.False(t, result.IsError)
+
+			textContent := getTextResult(t, result)
+			var returnedUser MinimalUser
+			err = json.Unmarshal([]byte(textContent.Text), &returnedUser)
+			require.NoError(t, err)
+			assert.Equal(t, "testuser", returnedUser.Login)
+		})
+	}
+}
+
 func Test_GetMe_IFC_FeatureFlag(t *testing.T) {
 	t.Parallel()
 

pkg/github/helper_test.go

@@ -323,6 +323,16 @@ func createMCPRequest(args any) mcp.CallToolRequest {
 	}
 }
 
+// createMCPRequestWithRawArguments creates a CallToolRequest with the given raw JSON arguments.
+// Use nil or an empty slice to simulate clients that omit the arguments field.
+func createMCPRequestWithRawArguments(args json.RawMessage) mcp.CallToolRequest {
+	return mcp.CallToolRequest{
+		Params: &mcp.CallToolParamsRaw{
+			Arguments: args,
+		},
+	}
+}
+
 // Well-known MCP client names used in tests.
 const (
 	ClientNameVSCodeInsiders = "Visual Studio Code - Insiders"