Fixed test setup

tests/PixiEditor.Tests/PixiEditorTest.cs

@@ -35,11 +35,12 @@ public class PixiEditorTest
             IWindow window = app.CreateMainWindow();
             window.IsVisible = false;
             window.Initialize();
-            DrawingBackendApi.InitializeBackend(engine.RenderApi);
+            DrawingBackendApi.SetupBackend(new SkiaDrawingBackend(), new DrawieRenderingDispatcher());
         }
         catch (Exception ex)
         {
-            DrawingBackendApi.SetupBackend(new SkiaDrawingBackend(), new DrawieRenderingDispatcher());
+            if(!DrawingBackendApi.HasBackend)
+                DrawingBackendApi.SetupBackend(new SkiaDrawingBackend(), new DrawieRenderingDispatcher());
         }
     }
 }

tests/PixiEditor.Tests/SerializationTests.cs

@@ -12,19 +12,8 @@ using PixiEditor.Parser.Skia.Encoders;
 
 namespace PixiEditor.Tests;
 
-public class SerializationTests
+public class SerializationTests : PixiEditorTest
 {
-    public SerializationTests()
-    {
-        if (DrawingBackendApi.HasBackend)
-        {
-            return;
-        }
-
-        SkiaDrawingBackend skiaDrawingBackend = new SkiaDrawingBackend();
-        DrawingBackendApi.SetupBackend(skiaDrawingBackend, new DrawieRenderingDispatcher());
-    }
-
     [Fact]
     public void TestThatAllPaintablesHaveFactories()
     {