Use Constructor / Dispose instead of [Before(Test)] / [After(Test)]

Note that this fails the two test with the [NotInParallel] attribute, i.e. FilterPropertyThrowing and ExceptionFormatterThrowing.

The [Test Set Ups][1] and [Test Clean Ups][2] documentation mentions respectively:

> Most setup for a test can be performed in the constructor (think setting up mocks, assigning fields.)

and

> TUnit supports having your test class implement `IDisposable` or `IAsyncDisposable`. These will be called after your test has finished executing.

So I'm not sure what's the difference between Custructor/Dispose and [Before(Test)] / [After(Test)] attributes.

[1]: https://thomhurst.github.io/TUnit/docs/tutorial-extras/setup
[2]: https://thomhurst.github.io/TUnit/docs/tutorial-extras/cleanup

tests/Log4NetTextFormatterTest.cs

@@ -13,10 +13,10 @@
 
 namespace Serilog.Formatting.Log4Net.Tests;
 
-public sealed class Log4NetTextFormatterTest
+public sealed class Log4NetTextFormatterTest : IDisposable
 {
-    private TextWriter? _selfLogWriter;
-    private string? SelfLogValue => _selfLogWriter?.ToString();
+    private readonly TextWriter _selfLogWriter;
+    private string? SelfLogValue => _selfLogWriter.ToString();
 
     /// <summary>
     /// Create a <see cref="DictionaryValue"/> containing two entries, mapping scalar values 1 to "one" and "two" to 2.
@@ -40,19 +40,16 @@ private static LogEvent CreateLogEvent(LogEventLevel level = Events.LogEventLeve
         );
     }
 
-    [Before(Test)]
-    public void EnableSelfLog()
+    public Log4NetTextFormatterTest()
     {
         _selfLogWriter = new StringWriter();
         Debugging.SelfLog.Enable(_selfLogWriter);
     }
 
-    [After(Test)]
-    public void DisableSelfLog()
+    public void Dispose()
     {
         Debugging.SelfLog.Disable();
-        _selfLogWriter?.Dispose();
-        _selfLogWriter = null;
+        _selfLogWriter.Dispose();
     }
 
     [Test]