diff --git a/tests/utils/canonicalize.test.js b/tests/utils/canonicalize.test.js
new file mode 100644
index 0000000..d6af050
--- /dev/null
+++ b/tests/utils/canonicalize.test.js
@@ -0,0 +1,38 @@
+import {
+  canonicalizePathname,
+  normalizeUrl,
+} from "../../src/utils/canonicalize.js";
+
+describe("canonicalizePathname", () => {
+  test("replaces numeric path segments with :id", () => {
+    expect(canonicalizePathname("/users/123/posts/456")).toBe(
+      "/users/:id/posts/:id",
+    );
+  });
+
+  test("replaces UUID path segments with :uuid", () => {
+    expect(
+      canonicalizePathname(
+        "/teams/550e8400-e29b-41d4-a716-446655440000/members",
+      ),
+    ).toBe("/teams/:uuid/members");
+  });
+
+  test("replaces high-entropy path segments with :id", () => {
+    expect(canonicalizePathname("/objects/a1b2c3d4e5f6")).toBe(
+      "/objects/:id",
+    );
+  });
+
+  test("keeps the root path as /", () => {
+    expect(canonicalizePathname("/")).toBe("/");
+  });
+});
+
+describe("normalizeUrl", () => {
+  test("removes query and hash while canonicalizing the pathname", () => {
+    expect(
+      normalizeUrl("https://api.example.com/users/123?include=posts#details"),
+    ).toBe("https://api.example.com/users/:id");
+  });
+});