From where does Environment.GetEnvironmentVariable pick its value in nunit and referenced blazor web assembly

I was actually trying this code section in NUnit .

using NUnit.Framework;namespace BlazorClientApp.Tests{    public class CounterTests    {        [Test]        public void CounterComponent_ShouldHaveInitialCountZero()        {            var envVariable = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT");            Assert.AreEqual("MyCheck", envVariable);        }    }}

I have already referenced this nunit project with my blazor wasm project.Here i was expecting that it will give me wasm environment variable but it's returning null what could be the reason.