public async Task ReturnHelloWorld()
    {
        // arrange
        var app    = new WebApplication();
        var client = app.CreateClient();

        // act
        var response = await client.GetAsync("/");

        // assert
        response.EnsureSuccessStatusCode();
        string responseString = await response.Content.ReadAsStringAsync();

        Assert.Equal("Hello World!", responseString);
    }