diff --git a/au/BUILD.bazel b/au/BUILD.bazel
index 6f5ac26f..826f55b8 100644
--- a/au/BUILD.bazel
+++ b/au/BUILD.bazel
@@ -47,6 +47,23 @@ cc_library(
     visibility = ["//visibility:public"],
 )
 
+cc_test(
+    name = "fwd_test",
+    size = "small",
+    srcs = [
+        "code/au/fwd_test.cc",
+        "code/au/fwd_test_lib.cc",
+        "code/au/fwd_test_lib.hh",
+    ],
+    deps = [
+        ":fwd",
+        ":io",
+        ":quantity",
+        ":units",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_library(
     name = "io",
     hdrs = ["code/au/io.hh"],
diff --git a/au/code/au/fwd_test.cc b/au/code/au/fwd_test.cc
new file mode 100644
index 00000000..67c5ded4
--- /dev/null
+++ b/au/code/au/fwd_test.cc
@@ -0,0 +1,29 @@
+// Copyright 2024 Aurora Operations, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "au/fwd_test_lib.hh"
+#include "au/quantity.hh"
+#include "au/units/meters.hh"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+using ::testing::StrEq;
+
+namespace au {
+
+TEST(Fwd, CanCallFunctionDeclaredWithOnlyFwdFiles) {
+    EXPECT_THAT(print_to_string(meters(1)), StrEq("1 m"));
+}
+
+}  // namespace au
diff --git a/au/code/au/fwd_test_lib.cc b/au/code/au/fwd_test_lib.cc
new file mode 100644
index 00000000..14ea6a9d
--- /dev/null
+++ b/au/code/au/fwd_test_lib.cc
@@ -0,0 +1,32 @@
+// Copyright 2024 Aurora Operations, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "au/fwd_test_lib.hh"
+
+#include <sstream>
+#include <string>
+
+#include "au/io.hh"
+#include "au/quantity.hh"
+#include "au/units/meters.hh"
+
+namespace au {
+
+std::string print_to_string(const QuantityI<Meters> &q) {
+    std::ostringstream oss;
+    oss << q;
+    return oss.str();
+}
+
+}  // namespace au
diff --git a/au/code/au/fwd_test_lib.hh b/au/code/au/fwd_test_lib.hh
new file mode 100644
index 00000000..c870897d
--- /dev/null
+++ b/au/code/au/fwd_test_lib.hh
@@ -0,0 +1,26 @@
+// Copyright 2024 Aurora Operations, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <string>
+
+#include "au/fwd.hh"
+#include "au/units/meters_fwd.hh"
+
+namespace au {
+
+std::string print_to_string(const QuantityI<Meters> &q);
+
+}  // namespace au