diff --git a/X10D.Tests/src/Time/TimeSpanParserTests.cs b/X10D.Tests/src/Time/TimeSpanParserTests.cs
index b671070..04149c5 100644
--- a/X10D.Tests/src/Time/TimeSpanParserTests.cs
+++ b/X10D.Tests/src/Time/TimeSpanParserTests.cs
@@ -7,9 +7,26 @@ namespace X10D.Tests.Time;
 public class TimeSpanParserTests
 {
     [TestMethod]
-    public void TryParse_ShouldThrow_GivenNullString()
+    public void TryParse_ShouldReturnTrue_GivenWellFormedTimeSpan()
     {
-        string? value = null;
-        Assert.ThrowsException<ArgumentNullException>(() => TimeSpanParser.TryParse(value!, out _));
+        bool result = TimeSpanParser.TryParse("3d6h", out TimeSpan timeSpan);
+        Assert.IsTrue(result);
+        Assert.AreEqual(TimeSpan.FromDays(3) + TimeSpan.FromHours(6), timeSpan);
+    }
+
+    [TestMethod]
+    public void TryParse_ShouldReturnFalse_GivenMalformedTimeSpan()
+    {
+        bool result = TimeSpanParser.TryParse("asdf", out TimeSpan timeSpan);
+        Assert.IsFalse(result);
+        Assert.AreEqual(default, timeSpan);
+    }
+
+    [TestMethod]
+    public void TryParse_ShouldReturnFalse_GivenNull()
+    {
+        bool result = TimeSpanParser.TryParse(null, out TimeSpan timeSpan);
+        Assert.IsFalse(result);
+        Assert.AreEqual(default, timeSpan);
     }
 }