test tweak

test/EngineTest.cs

@@ -1028,11 +1028,13 @@ namespace Tests
             }
         }
 
+        static bool timeDilationActive;
         class ReadDilatedDeltaTimeEngine : Engine
         {
             public override void Update(double dt)
             {
                 dilatedDeltaTime = dt;
+                timeDilationActive = TimeDilationActive;
             }
         }
 
@@ -1051,10 +1053,12 @@ namespace Tests
             world.Update(0.5); // 0.3 and 0.375
 
             dilatedDeltaTime.Should().BeApproximately(0.3375, 0.01);
+            timeDilationActive.Should().BeTrue();
 
             world.Update(5);
 
             dilatedDeltaTime.Should().BeApproximately(5, 0.01);
+            timeDilationActive.Should().BeFalse();
         }
 
         static double undilatedDeltaTime;