diff --git a/packages/open-next/src/core/routing/middleware.ts b/packages/open-next/src/core/routing/middleware.ts
index ebdf1bf5a..d768dd0ef 100644
--- a/packages/open-next/src/core/routing/middleware.ts
+++ b/packages/open-next/src/core/routing/middleware.ts
@@ -28,6 +28,14 @@ type MiddlewareOutputEvent = InternalEvent & {
   externalRewrite?: boolean;
 };
 
+type Middleware = (request: Request) => Response | Promise<Response>;
+type MiddlewareLoader = () => Promise<{ default: Middleware }>;
+
+function defaultMiddlewareLoader() {
+  // @ts-expect-error - This is bundled
+  return import("./middleware.mjs");
+}
+
 // NOTE: As of Nextjs 13.4.13+, the middleware is handled outside the next-server.
 // OpenNext will run the middleware in a sandbox and set the appropriate req headers
 // and res.body prior to processing the next-server.
@@ -36,6 +44,7 @@ type MiddlewareOutputEvent = InternalEvent & {
 //    if res.end() is return, the parent needs to return and not process next server
 export async function handleMiddleware(
   internalEvent: InternalEvent,
+  middlewareLoader: MiddlewareLoader = defaultMiddlewareLoader,
 ): Promise<MiddlewareOutputEvent | InternalResult> {
   const { query } = internalEvent;
   const normalizedPath = localizePath(internalEvent);
@@ -53,8 +62,7 @@ export async function handleMiddleware(
   const url = initialUrl.toString();
   // console.log("url", url, normalizedPath);
 
-  // @ts-expect-error - This is bundled
-  const middleware = await import("./middleware.mjs");
+  const middleware = await middlewareLoader();
 
   const result: Response = await middleware.default({
     geo: {
@@ -73,7 +81,7 @@ export async function handleMiddleware(
     },
     url,
     body: convertBodyToReadableStream(internalEvent.method, internalEvent.body),
-  });
+  } as unknown as Request);
   const statusCode = result.status;
 
   /* Apply override headers from middleware
diff --git a/packages/tests-unit/tests/core/routing/middleware.test.ts b/packages/tests-unit/tests/core/routing/middleware.test.ts
new file mode 100644
index 000000000..2d736df15
--- /dev/null
+++ b/packages/tests-unit/tests/core/routing/middleware.test.ts
@@ -0,0 +1,260 @@
+import { handleMiddleware } from "@opennextjs/aws/core/routing/middleware.js";
+import { convertFromQueryString } from "@opennextjs/aws/core/routing/util.js";
+import { InternalEvent } from "@opennextjs/aws/types/open-next.js";
+import { toReadableStream } from "@opennextjs/aws/utils/stream.js";
+import { vi } from "vitest";
+
+vi.mock("@opennextjs/aws/adapters/config/index.js", () => ({
+  NextConfig: {},
+  MiddlewareManifest: {
+    sortedMiddleware: ["/"],
+    middleware: {
+      "/": {
+        files: [
+          "prerender-manifest.js",
+          "server/edge-runtime-webpack.js",
+          "server/middleware.js",
+        ],
+        name: "middleware",
+        page: "/",
+        matchers: [
+          {
+            regexp:
+              "^(?:\\/(_next\\/data\\/[^/]{1,}))?(?:\\/((?!_next|favicon.ico|match|static|fonts|api\\/auth|og).*))(.json)?[\\/#\\?]?$",
+            originalSource:
+              "/((?!_next|favicon.ico|match|static|fonts|api/auth|og).*)",
+          },
+        ],
+        wasm: [],
+        assets: [],
+      },
+    },
+    functions: {},
+    version: 2,
+  },
+}));
+
+vi.mock("@opennextjs/aws/core/routing/i18n/index.js", () => ({
+  localizePath: (event: InternalEvent) => event.rawPath,
+}));
+
+const middleware = vi.fn();
+const middlewareLoader = vi.fn().mockResolvedValue({
+  default: middleware,
+});
+
+type PartialEvent = Partial<
+  Omit<InternalEvent, "body" | "rawPath" | "query">
+> & { body?: string };
+
+function createEvent(event: PartialEvent): InternalEvent {
+  const [rawPath, qs] = (event.url ?? "/").split("?", 2);
+  return {
+    type: "core",
+    method: event.method ?? "GET",
+    rawPath,
+    url: event.url ?? "/",
+    body: Buffer.from(event.body ?? ""),
+    headers: event.headers ?? {},
+    query: convertFromQueryString(qs ?? ""),
+    cookies: event.cookies ?? {},
+    remoteAddress: event.remoteAddress ?? "::1",
+  };
+}
+
+beforeEach(() => {
+  vi.clearAllMocks();
+});
+
+/**
+ * Ideally these tests would be broken up and tests smaller parts of the middleware rather than the entire function.
+ */
+describe("handleMiddleware", () => {
+  it("should bypass middlware for internal requests", async () => {
+    const event = createEvent({
+      headers: {
+        "x-isr": "1",
+      },
+    });
+    const result = await handleMiddleware(event, middlewareLoader);
+
+    expect(middlewareLoader).not.toBeCalled();
+    expect(result).toEqual(event);
+  });
+
+  it("should invoke middlware with redirect", async () => {
+    const event = createEvent({});
+    middleware.mockResolvedValue({
+      status: 302,
+      headers: new Headers({
+        location: "/redirect",
+      }),
+    });
+    const result = await handleMiddleware(event, middlewareLoader);
+
+    expect(middlewareLoader).toBeCalled();
+    expect(result.statusCode).toEqual(302);
+    expect(result.headers.location).toEqual("/redirect");
+  });
+
+  it("should invoke middlware with external redirect", async () => {
+    const event = createEvent({});
+    middleware.mockResolvedValue({
+      status: 302,
+      headers: new Headers({
+        location: "http://external/redirect",
+      }),
+    });
+    const result = await handleMiddleware(event, middlewareLoader);
+
+    expect(middlewareLoader).toBeCalled();
+    expect(result.statusCode).toEqual(302);
+    expect(result.headers.location).toEqual("http://external/redirect");
+  });
+
+  it("should invoke middlware with rewrite", async () => {
+    const event = createEvent({
+      headers: {
+        host: "localhost",
+      },
+    });
+    middleware.mockResolvedValue({
+      headers: new Headers({
+        "x-middleware-rewrite": "http://localhost/rewrite",
+      }),
+    });
+    const result = await handleMiddleware(event, middlewareLoader);
+
+    expect(middlewareLoader).toBeCalled();
+    expect(result).toEqual({
+      ...event,
+      rawPath: "/rewrite",
+      url: "/rewrite",
+      responseHeaders: {
+        "x-middleware-rewrite": "http://localhost/rewrite",
+      },
+      externalRewrite: false,
+    });
+  });
+
+  it("should invoke middlware with rewrite with __nextDataReq", async () => {
+    const event = createEvent({
+      url: "/rewrite?__nextDataReq=1&key=value",
+      headers: {
+        host: "localhost",
+      },
+    });
+    middleware.mockResolvedValue({
+      headers: new Headers({
+        "x-middleware-rewrite": "http://localhost/rewrite?newKey=value",
+      }),
+    });
+    const result = await handleMiddleware(event, middlewareLoader);
+
+    expect(middlewareLoader).toBeCalled();
+    expect(result).toEqual({
+      ...event,
+      rawPath: "/rewrite",
+      url: "/rewrite",
+      responseHeaders: {
+        "x-middleware-rewrite": "http://localhost/rewrite?newKey=value",
+      },
+      query: {
+        __nextDataReq: "1",
+        newKey: "value",
+      },
+      externalRewrite: false,
+    });
+  });
+
+  it("should invoke middlware with external rewrite", async () => {
+    const event = createEvent({
+      headers: {
+        host: "localhost",
+      },
+    });
+    middleware.mockResolvedValue({
+      headers: new Headers({
+        "x-middleware-rewrite": "http://external/rewrite",
+      }),
+    });
+    const result = await handleMiddleware(event, middlewareLoader);
+
+    expect(middlewareLoader).toBeCalled();
+    expect(result).toEqual({
+      ...event,
+      rawPath: "http://external/rewrite",
+      url: "http://external/rewrite",
+      responseHeaders: {
+        "x-middleware-rewrite": "http://external/rewrite",
+      },
+      externalRewrite: true,
+    });
+  });
+
+  it("should map x-middleware-request- headers as request headers", async () => {
+    const event = createEvent({});
+    middleware.mockResolvedValue({
+      headers: new Headers({
+        "x-middleware-request-custom-header": "value",
+      }),
+    });
+    const result = await handleMiddleware(event, middlewareLoader);
+
+    expect(middlewareLoader).toBeCalled();
+    expect(result).toEqual({
+      ...event,
+      headers: {
+        "custom-header": "value",
+      },
+      responseHeaders: {},
+      externalRewrite: false,
+    });
+  });
+
+  it("should return a response from middleware", async () => {
+    const event = createEvent({});
+    const body = toReadableStream("Hello, world!");
+
+    middleware.mockResolvedValue({
+      status: 200,
+      headers: new Headers(),
+      body,
+    });
+    const result = await handleMiddleware(event, middlewareLoader);
+
+    expect(middlewareLoader).toBeCalled();
+    expect(result).toEqual({
+      type: "core",
+      statusCode: 200,
+      headers: {},
+      body,
+      isBase64Encoded: false,
+    });
+  });
+
+  it("should return a response from middleware with set-cookie header", async () => {
+    const event = createEvent({});
+    const body = toReadableStream("Hello, world!");
+
+    middleware.mockResolvedValue({
+      status: 200,
+      headers: new Headers({
+        "set-cookie": "cookie=value",
+      }),
+      body,
+    });
+    const result = await handleMiddleware(event, middlewareLoader);
+
+    expect(middlewareLoader).toBeCalled();
+    expect(result).toEqual({
+      type: "core",
+      statusCode: 200,
+      headers: {
+        "set-cookie": ["cookie=value"],
+      },
+      body,
+      isBase64Encoded: false,
+    });
+  });
+});