Testing with `Tap` never ends

Question

I am using Tap with Fastify inject to test my Server implementation. If I run my test cases using yarn run test, it executes all the test and evaluates correctly. However, it never shuts down to show the summary. Instead, I need to manually enter the keyboard interrupt in the terminal to stop the tests and get the result summary.

My observation is that the const responseData = DataUrl() function inside the route, that processes the request before sending the output, is causing the problem. This function when removed solves my issue. Although, its very rudimentary for this demo, I have a lot of logic inside DataUrl() function

How can I fix this?

Here is my output

 RUNS  src/__tests__/dataurl.test.ts 1 failed of 1 20.431s

Asserts:  1 pass  0 fail  1 of 1 complete
Suites:   1 pass  0 fail  1 of 2 complete

Package.json

"scripts": {
   "test": "tap  --node-arg=--require=ts-node/register"
 },

Route implementation

fastifyServer.post("/dataurl", async (request, response) => {
        const responseData = DataUrl();
        response
            .code(200)
            .header("Content-Type", "application/json; charset=utf-8")
            .send(responseData);
    });

DataUrl function (in another file)

export const DataUrl = (): string => {
    return "hello";
};

Test implementation

test("Check data url", async (t) => {
    const fastify = app();

    t.after(async () => await fastify.close());

    const res = await fastify.inject({
        url: "/dataurl",
        method: "POST",
    });

    console.log(res);
    t.equal(res.statusCode, 204);
});