How can I enable trace output in NUnit 3's Visual Studio adapter?

According to this discussion, they removed that because of technical reasons.

An alternative solution might be something like this:

using NUnit.Framework;

    namespace MyUnitTest {
        [TestFixture]
        public class UnitTest1 {
            [Test()]
            public void Test1() {
                var x = "Before Test";
                TestContext.Progress.WriteLine(x);
                x = "Hello";
                TestContext.Progress.WriteLine(x);
                Assert.IsTrue(x == "Hello");
                x = "After Test";
                TestContext.Progress.WriteLine(x);
            }
        }
    }

With the given result:

NUnit Adapter 3.4.1.0: Test execution started Running selected tests in C:\ProjectPath\MyUnitTest.dll NUnit3TestExecutor converted 1 of 1
NUnit test cases Before Test Hello After Test NUnit Adapter 3.4.1.0:
Test execution complete
========== Test execution complete: 1 run(0:00:00,7660762) ==========

Conclusion

You can't use Trace anymore on outputs for NUnit.