diff --git a/Tests/p4rseTests/Unsupported.swift b/Tests/p4rseTests/Unsupported.swift
new file mode 100644
index 0000000..5e8bbbc
--- /dev/null
+++ b/Tests/p4rseTests/Unsupported.swift
@@ -0,0 +1,56 @@
+// p4rse, Copyright 2026, Will Hawkins
+//
+// This file is part of p4rse.
+//
+// This file is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+import Common
+import Foundation
+import Macros
+import P4Lang
+import Runtime
+import SwiftTreeSitter
+import Testing
+import TreeSitter
+import TreeSitterP4
+
+@testable import P4Compiler
+
+@Test func test_unsupported_annotations() async throws {
+  let simple_annotated_parser_declaration = """
+    @testing parser main_parser() {
+       state start {
+           transition start;
+       }
+    };
+    """
+  #expect(
+    #RequireErrorResult(
+      Error(withMessage: "{0, 8}: Annotations in parser type are not yet handled."),
+      Program.Compile(simple_annotated_parser_declaration)))
+}
+
+@Test func test_unsupported_annotations_state() async throws {
+  let simple_annotated_parser_declaration = """
+    parser main_parser() {
+       @testing state start {
+           transition start;
+       }
+    };
+    """
+  #expect(
+    #RequireErrorResult(
+      Error(withMessage: "{26, 8}: Annotations in parser state are not yet handled."),
+      Program.Compile(simple_annotated_parser_declaration)))
+}