Auto Testing .Net Core API Project

To automate the testing of a .NET Core API project, you can use a testing framework such as NUnit or xUnit, which are popular for .NET Core projects.

Here are some steps to get started,

1. Add a separate project to your solution for your tests.
2. Install the testing framework of your choice (e.g., NUnit, xUnit) using the NuGet Package Manager.
3. Write test cases for your API endpoints, including positive and negative scenarios.
4. Use the testing framework's assertions to ensure the API endpoints return the expected results.
5. Run the tests using the testing framework's test runner, which can be done from the command line or within Visual Studio.
6. Refine your tests as needed to cover more scenarios and edge cases.

Here's an example of a simple test using NUnit that checks that the API's "GetAll" endpoint returns a 200 OK status code:

using System;
using System.Net;
using NUnit.Framework;

[TestFixture]
public class ApiTests
{
    [Test]
    public void TestGetAll()
    {
        var client = new WebClient();
        var result = client.DownloadString("http://localhost:5000/api/items");

        Assert.That(result, Is.Not.Null);
        Assert.That(result, Is.Not.Empty);
        Assert.That(result.Contains("item1"));
        Assert.That(result.Contains("item2"));
        Assert.That(result.Contains("item3"));
        Assert.That(client.ResponseHeaders["Content-Type"], Is.EqualTo("application/json; charset=utf-8"));
        Assert.That(client.ResponseHeaders["Access-Control-Allow-Origin"], Is.EqualTo("*"));
        Assert.That(client.ResponseHeaders["Access-Control-Allow-Methods"], Is.EqualTo("GET, POST, PUT, DELETE, OPTIONS"));
        Assert.That(client.ResponseHeaders["Access-Control-Allow-Headers"], Is.EqualTo("Origin, X-Requested-With, Content-Type, Accept"));
        Assert.That(client.ResponseHeaders["Access-Control-Expose-Headers"], Is.EqualTo("X-Pagination"));
        Assert.That(client.ResponseHeaders["Access-Control-Max-Age"], Is.EqualTo("600"));
        Assert.That(client.ResponseHeaders["X-Pagination-Total-Count"], Is.EqualTo("3"));
        Assert.That(client.ResponseHeaders["X-Pagination-Total-Pages"], Is.EqualTo("1"));
        Assert.That(client.ResponseHeaders["X-Pagination-Current-Page"], Is.EqualTo("1"));
        Assert.That(client.ResponseHeaders["X-Pagination-Page-Size"], Is.EqualTo("10"));
    }
}

This test uses the WebClient class to make a GET request to the API's "/api/items" endpoint and then checks that the response includes the expected items and the expected HTTP headers. This is just one example of a test you could write, and you'll likely want to write more tests to cover more scenarios.