3 files changed, 45 insertions, 0 deletions
diff --git a/ttwhy/routers/echo.tests.cpp b/ttwhy/routers/echo.tests.cpp
index f12d08b..c6ea10a 100644
--- a/ttwhy/routers/echo.tests.cpp
+++ b/ttwhy/routers/echo.tests.cpp
@@ -45,8 +45,32 @@ namespace
           token, buffers);
     }
   };
+
+  struct incomplete_router_no_policy
+  {
+    auto process(ttwhy::scanners::input_event) -> asio::awaitable<void>;
+  };
+
+  struct incomplete_router_no_process
+  {
+    using terminal_policy = ttwhy::scanners::xterm_policy;
+  };
+
+  struct incomplete_router_wrong_return
+  {
+    using terminal_policy = ttwhy::scanners::xterm_policy;
+    auto process(ttwhy::scanners::input_event) -> void;
+  };
 }  // namespace
 
+TEST_CASE("The router concept validates router candidate interfaces", "[router][concept]")
+{
+  STATIC_REQUIRE(ttwhy::router<ttwhy::routers::echo<mock_stream>>);
+  STATIC_REQUIRE_FALSE(ttwhy::router<incomplete_router_no_policy>);
+  STATIC_REQUIRE_FALSE(ttwhy::router<incomplete_router_no_process>);
+  STATIC_REQUIRE_FALSE(ttwhy::router<incomplete_router_wrong_return>);
+}
+
 SCENARIO("The echo router handles terminal navigation within the valid printed area", "[router][echo]")
 {
   GIVEN("An initialized echo router with a mock stream")
diff --git a/ttwhy/routers/mod.cppm b/ttwhy/routers/mod.cppm
index fbab282..f5e151b 100644
--- a/ttwhy/routers/mod.cppm
+++ b/ttwhy/routers/mod.cppm
@@ -1,3 +1,4 @@
 export module ttwhy.routers;
 
 export import :echo;
+export import :router_concepts;
diff --git a/ttwhy/routers/router_concepts.cppm b/ttwhy/routers/router_concepts.cppm
new file mode 100644
index 0000000..ce143cb
--- /dev/null
+++ b/ttwhy/routers/router_concepts.cppm
@@ -0,0 +1,20 @@
+module;
+
+#include <asio.hpp>
+
+#include <concepts>
+
+export module ttwhy.routers:router_concepts;
+
+import ttwhy.scanners;
+
+namespace ttwhy
+{
+
+  export template<typename Candidate>
+  concept router = requires(Candidate candidate, scanners::input_event event) {
+    typename Candidate::terminal_policy;
+    { candidate.process(event) } -> std::same_as<asio::awaitable<void>>;
+  };
+
+}  // namespace ttwhy