in my main project, I am using MimeKit and MailKit to create MimeMessage object

public MimeMailClient()
  {
    mimeMessage = new MimeMessage();
  }

in my Unit test project, I am using Moq (https://www.moqthis.com/) and NUnit (https://nunit.org/).
when i create main project constructor, it throws exception

**Code **

  [TestFixture]
    public class TestMailSend
    {
        [Test]
        public void SendMailWithHtmlBody()
        {
            var xx = new MimeMailClient();
        }
    }

**Exception **
System.IO.FileNotFoundException: ‘Could not load file or assembly ‘System.Runtime.CompilerServices.Unsafe, Version=4.0.4.1, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’ or one of its dependencies. The system cannot find the file specified.’

enter image description here

How can i fix this issue?