OneTimeSetup method being called 4 times when tests have 4 TestFixtures

Question

I am having an issue where my Parallelizable UI Selenium tests are calling the [OneTimeSetup] method multiple times and as a result creating multiple Testrail test runs.

In my base class, my [OneTimeSetup] method, I am creating a testrun in Testrail. My tests contain 4 [TestFixtures] and all tests in each fixture call the [OneTimeSetup] method once per fixture.

I want the [OneTimeSetup] method to be called only once even if I have 4 (or more) [TestFixtures].

Is there an NUnit attribute that will run only once over multiple [TestFixtures]?

Code:

    public ThreadLocal<IWebDriver> driver = new ThreadLocal<IWebDriver>();

    [OneTimeSetUp]
    public async Task OneTimeSetUp()
    {
        RestRequest newRequest = new RestRequest($"index.php?/api/v2/add_run/{project_id}", Method.Post);
        string authInfo = Base64StringConverter.GetBase64String("email:password");
        newRequest.AddHeader("Authorization", "Basic " + authInfo);
        newRequest.AddHeader("Content-Type", "application/json");

        newRequest.RequestFormat = DataFormat.Json;
        newRequest.AddJsonBody(new { assignedto_id = 1, suite_id = 1111, name = "UI Nightly Regression Test Run", refs = "UI Auto Tests", description = "This is a description of the test", include_all = true });

        //act
        var newResponse = await restClient.ExecuteAsync(newRequest);
        HttpStatusCode statusCode = newResponse.StatusCode;
        JObject responseData = JObject.Parse(newResponse.Content);
        JToken jToken = responseData.SelectToken("id");
        string test = jToken.ToString();
        Console.WriteLine(test.ToString());

        //assert
        Console.WriteLine(newResponse.Content);
        Console.WriteLine(newResponse.Request);
        Console.WriteLine((int)statusCode);
        Assert.That((int)statusCode, Is.EqualTo(200));
    }

Example Test in Fixture:

    [TestFixture]
    [Parallelizable(ParallelScope.Self)]
    [Category("Dashboard")]
    public class DashboardTests : Base
    {

        [Test, TestCaseSource(nameof(LoginData), Category = "C1886640")]
        [Category("Smoke")]

Answer 1

I found the answer here: Is it possible to have a [OneTimeSetup] for ALL tests?

Adding the following check to my base class meant that this was run only once over multiple [TestFixtures].

private static bool FirstInitializationFlag = true;

[OneTimeSetUp]
public void PrepareTestsStart()
{
    if (FirstInitializationFlag)
    {
        FirstInitializationFlag = false;
        
        // Do actions before all test classes to run
    }
}