Theorem.MockNet.Http

The package provides a friendly mocking framework to unit test the System.Net.Http namespace.

Main features:

• works with any .NET unit testing and mocking library
• convenient syntax to setup http request and response messages and their properties
• ability to validate request headers and content matching with lambda predicates
• ability to specify status code, headers and content to be returned from the HTTP call

Examples:

A quick and simple example. This sample mocks a call to the https://jsonplaceholder.typeicode.com/todos/1 resource to return a status code of 201 Created.

using Theorem.MockNet.Http;
using Xunit; // used here for Asserting.

...

var mock = new MockHttpClient();

mock.SetupGet("/todos/1").ReturnsAsync(201);

var result = await mock.Object.GetAsync("/todos/1");

Assert.Equal(201, (int)result.StatusCode);

Lets look at a more real life example:

Todo model

public class Todo
{
    public int UserId { get; set; }
    public int Id { get; set; }
    public string Title { get; set; }
    public bool Completed { get; set; }

    public Todo() {}

    public Todo(int id, int userId, string title) => (Id, UserId, Title) = (id, userId, title);
}

Service to consume the api

using System;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;
using SystemStringContent = System.Net.Http.StringContent;

public class TodoService
{
    private HttpClient _httpClient;

    public TodoService(HttpClient httpClient)
    {
        this._httpClient = httpClient;
    }

    public Task<Todo> GetAsync(int id) => GetAsync($"/todos/{id}");

    private async Task<Todo> GetAsync(string requestUri)
    {
        var response = await this._httpClient.GetAsync(requestUri);

        if (!response.IsSuccessStatusCode)
        {
            throw new Exception("Todo not found");
        }

        var json = await response.Content.ReadAsStringAsync();

        return JsonConvert.DeserializeObject<Todo>(json);
    }

    public async Task<Todo> CreateAsync(Todo todo)
    {
        var content = new SystemStringContent(JsonConvert.SerializeObject(todo), Encoding.UTF8, "application/json");

        var response = await this._httpClient.PostAsync("/todos", content);

        if (response.IsSuccessStatusCode &&
            response.Headers.Location is Uri uri)
        {
            return await GetAsync(uri.ToString());
        }

        throw new Exception("Error creating todo");
    }
}

And the unit test for the TodoService

using Theorem.MockNet.Http;
using Xunit;

public class TodoServiceTests
{
    private TodoService service;
    private MockHttpClient mock;

    public TodoServiceTests()
    {
        this.mock = new MockHttpClient();
        this.service = new TodoService(mock.Object);
    }

    [Fact]
    public async Task GetAsync_should_return_expected_todo()
    {
        var expected = new Todo(1, 456, "go shopping");

        mock.SetupGet("/todos/1").ReturnsAsync(201, expected);

        var actual = await service.GetAsync(1);

        Assert.Equal(expected.Id, actual.Id);
        Assert.Equal(expected.UserId, actual.UserId);
        Assert.Equal(expected.Title, actual.Title);
        Assert.Equal(expected.Completed, actual.Completed);
    }

    [Fact]
    public async Task GetAsync_should_throw_exception_when_invalid_status_code_is_returned()
    {
        mock.SetupGet("/todos/1").ReturnsAsync(404);

        await Assert.ThrowsAsync<Exception>(() => service.GetAsync(1));
    }

    [Fact]
    public async Task CreateAsync_should_create_and_return_new_todo()
    {
        var todo = new Todo(0, 456, "go shopping");
        var expected = new Todo(2, 456, "go shopping");

        var responseHeaders = new HttpResponseHeaders();
        responseHeaders.Add("Location", $"https://localhost/todos/{expected.Id}");

        // pass lambda predicate to validate request content
        // response from the HTTP Post method will have 201 status code and Location header
        mock.SetupPost<Todo>("/todos",
            content: x => x.UserId == todo.UserId &&
                x.Title == todo.Title &&
                x.Completed == todo.Completed).ReturnsAsync(201, responseHeaders);

        mock.SetupGet($"/todos/{expected.Id}").ReturnsAsync(expected);

        var actual = await service.CreateAsync(todo);

        Assert.Equal(expected.Id, actual.Id);
        Assert.Equal(expected.UserId, actual.UserId);
        Assert.Equal(expected.Title, actual.Title);
        Assert.Equal(expected.Completed, actual.Completed);
    }

    [Fact]
    public async Task CreateAsync_should_throw_exception_when_invalid_status_code_is_returned()
    {
        mock.SetupPost("/todos").ReturnsAsync(404);

        await Assert.ThrowsAsync<Exception>(() => service.CreateAsync(new Todo()));
    }

    [Fact]
    public async Task CreateAsync_should_throw_exception_when_missing_location_header()
    {
        mock.SetupPost("/todos").ReturnsAsync(200);

        await Assert.ThrowsAsync<Exception>(() => service.CreateAsync(new Todo()));
    }
}

For more examples on how to test other HttpClient aspects including testing headers and content body being sent to the endpoint as well as headers being returned please see tests/MockNet.Tests/Playground.cs

About TheoremOne

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