C# End-to-end automated integration testing for Web API. More infromation available at https://andypalmer.dev/end-to-end-testing-mvc-signalr-api

ApiHttpClientHelper.cs

using Newtonsoft.Json;
using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading.Tasks;

public class ApiHttpClientHelper
{
    public HttpClient Client { get; }

    public ApiHttpClientHelper(HttpClient httpClient)
    {
        Client = httpClient;
    }

    public async Task<string> LoginHttpRequest()
    {
        string clientId = Environment.ClientId;
        string clientSecret = Environment.ClientSecret;

        var data = new StringContent($"grant_type=password&username={Environment.UserName}&password={Environment.Password}");
        var authToken = Encoding.ASCII.GetBytes($"{clientId}:{clientSecret}");

        Client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(authToken));

        var response = await Client.PostAsync($"{Environment.APIUrl}/token", data);
        string result = await response.Content.ReadAsStringAsync();

        if (response.IsSuccessStatusCode)
        {
            var loginResonse = JsonConvert.DeserializeObject<LoginResponse>(result);
            return loginResonse.access_token;
        }
        else
        {
            throw new Exception(result);
        }
    }

    public async Task<HttpResponseMessage> PostHttpRequest(string url, string data, string token = null)
    {
        if (string.IsNullOrEmpty(token))
        {
            token = await LoginHttpRequest();
        }
        Client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("bearer", token);
        var response = await Client.PostAsync(url, new StringContent(data, Encoding.UTF8, "application/json"));
        return response;
    }

    public async Task<HttpResponseMessage> PutHttpRequest(string url, string data, string token = null)
    {
        if (string.IsNullOrEmpty(token))
        {
            token = await LoginHttpRequest();
        }
        Client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("bearer", token);
        var response = await Client.PutAsync(url, new StringContent(data, Encoding.UTF8, "application/json"));
        return response;
    }

    public async Task<HttpResponseMessage> PatchHttpRequest(string url, string data, string token = null)
    {
        if (string.IsNullOrEmpty(token))
        {
            token = await LoginHttpRequest();
        }
        Client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("bearer", token);

        var request = new HttpRequestMessage(new HttpMethod("PATCH"), url)
        {
            Content = new StringContent(data, Encoding.UTF8, "application/json")
        };

        var response = await Client.SendAsync(request);
        return response;
    }
    public async Task<HttpResponseMessage> GetHttpRequest(string url, string token = null)
    {

        if (string.IsNullOrEmpty(token))
        {
            token = await LoginHttpRequest();
        }
        Client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("bearer", token);
        var request = new HttpRequestMessage(new HttpMethod("GET"), url);
        var response = await Client.SendAsync(request);

        return response;
    }
}