com.unity.uiwidgets/Tests/Editor/EditorExampleTest.cs

using System.Collections;
using NUnit.Framework;
using UnityEngine.TestTools;

class EditorExampleTest {
    [Test]
    public void EditorSampleTestSimplePasses() {
        // Use the Assert class to test conditions.
    }

    // A UnityTest behaves like a coroutine in PlayMode
    // and allows you to yield null to skip a frame in EditMode
    [UnityTest]
    public IEnumerator EditorSampleTestWithEnumeratorPasses() {
        // Use the Assert class to test conditions.
        // yield to skip a frame
        yield return null;
    }
}