diff --git a/tests/NetVips.Tests/IoFuncsTests.cs b/tests/NetVips.Tests/IoFuncsTests.cs
index a7901f68..e4d83c83 100644
--- a/tests/NetVips.Tests/IoFuncsTests.cs
+++ b/tests/NetVips.Tests/IoFuncsTests.cs
@@ -9,8 +9,11 @@ namespace NetVips.Tests
 
     public class IoFuncsTests : IClassFixture<TestsFixture>
     {
+        private readonly ITestOutputHelper _testOutputHelper;
+
         public IoFuncsTests(TestsFixture testsFixture, ITestOutputHelper output)
         {
+            _testOutputHelper = output;
             testsFixture.SetUpLogging(output);
         }
 
@@ -235,14 +238,24 @@ public void TestSetProgress()
 
             var im = Image.NewFromFile(Helper.JpegFile, access: Enums.Access.Sequential);
 
-            var lastPercent = 0;
+            void EvalCallback(Image image, VipsProgress progressStruct)
+            {
+                _testOutputHelper.WriteLine($"   run = {progressStruct.Run} (seconds of run time)");
+                _testOutputHelper.WriteLine($"   eta = {progressStruct.Eta} (estimated seconds left)");
+                _testOutputHelper.WriteLine($"   tpels = {progressStruct.TPels} (total number of pels)");
+                _testOutputHelper.WriteLine($"   npels = {progressStruct.NPels} (number of pels computed so far)");
+                _testOutputHelper.WriteLine($"   percent = {progressStruct.Percent} (percent complete)");
+                _testOutputHelper.WriteLine($"   active = {progressStruct.Start.Active} (timer active)");
+            }
 
-            var progress = new Progress<int>(percent => lastPercent = percent);
-            im.SetProgress(progress);
+            im.SetProgress(true);
+            im.SignalConnect(Enums.Signals.PreEval, EvalCallback);
+            im.SignalConnect(Enums.Signals.Eval, EvalCallback);
+            im.SignalConnect(Enums.Signals.PostEval, EvalCallback);
 
-            var buf = im.DzsaveBuffer("image-pyramid");
+            var buf = im.DzsaveBuffer("image-pyramid", suffix: ".png");
             Assert.True(buf.Length > 0);
-            Assert.True(lastPercent <= 100);
+            Assert.True(false);
         }
 
         [Fact]