tests: continue the climb to comprehensive test coverage

src/StevesBot.Worker.Tests/Unit/ActivityTests.cs

@@ -0,0 +1,14 @@
+namespace StevesBot.Worker.Tests.Unit;
+
+public class ActivityTests
+{
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldCreateAnInstance()
+  {
+    var activity = new Activity();
+
+    activity.Name.Should().Be(string.Empty);
+    activity.Type.Should().Be(ActivityType.Custom);
+    activity.State.Should().BeNull();
+  }
+}

src/StevesBot.Worker.Tests/Unit/UpdatePresenceDataTests.cs

@@ -2,5 +2,36 @@ namespace StevesBot.Worker.Tests.Unit;
 
 public class UpdatePresenceDataTests
 {
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldCreateAnInstance()
+  {
+    var updatePresenceData = new UpdatePresenceData();
 
+    updatePresenceData.Since.Should().BeNull();
+    updatePresenceData.Activities.Should().BeEmpty();
+    updatePresenceData.Status.Should().Be(PresenceStatus.Online);
+    updatePresenceData.Afk.Should().BeFalse();
+  }
+  
+  [Fact]
+  public void Constructor_WhenCalledAndPropertiesAreInitialized_ItShouldCreateAnInstance()
+  {
+    var since = 1;
+    var activities = new List<Activity>();
+    var status = "some_made_up_status";
+    var afk = true;
+    
+    var updatePresenceData = new UpdatePresenceData()
+    {
+      Since = since,
+      Activities = activities,
+      Status = status,
+      Afk = afk,
+    };
+    
+    updatePresenceData.Since.Should().Be(since);
+    updatePresenceData.Activities.Should().BeSameAs(activities);
+    updatePresenceData.Status.Should().Be(status);
+    updatePresenceData.Afk.Should().Be(afk);
+  }
 }

src/StevesBot.Worker/Handlers/WelcomeMessageHandler.cs

@@ -1,6 +1,4 @@
 using System.Globalization;
-using System.Text;
-
 namespace StevesBot.Worker.Handlers;
 
 internal static class WelcomeMessageHandler