diff --git a/BackendTests/Services/GameGroupTests.cs b/BackendTests/Services/GameGroupTests.cs
index 84fe963..70c70af 100644
--- a/BackendTests/Services/GameGroupTests.cs
+++ b/BackendTests/Services/GameGroupTests.cs
@@ -202,9 +202,24 @@ public class GameGroupTests
     public void SetAllInGame_SetsStateToInGame()
     {
         AddFullParty();
-        Assert.That(_gameGroup.Players, Has.All.Property(nameof(IPlayer.State)).Not.EqualTo(State.Ready));
-        _gameGroup.SetAllInGame();
-        Assert.That(_gameGroup.Players, Has.All.Property(nameof(IPlayer.State)).EqualTo(State.InGame));
+        _gameGroup.Players.ForEach(player => player.State = State.Ready);
+        Assert.That(_gameGroup.Players, Has.All.Property(nameof(IPlayer.State)).EqualTo(State.Ready));
+
+        var allInGame = _gameGroup.SetAllInGame();
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(allInGame, Is.True);
+            Assert.That(_gameGroup.Players, Has.All.Property(nameof(IPlayer.State)).EqualTo(State.InGame));
+        });
+    }
+
+    [Test]
+    public void SetAllInGame_SetStateToInGame_WhenNotAllReady()
+    {
+        AddFullParty();
+        var allInGame = _gameGroup.SetAllInGame();
+        Assert.That(allInGame, Is.False);
     }
 
     [Test]
diff --git a/pac-man-board-game/Services/GameGroup.cs b/pac-man-board-game/Services/GameGroup.cs
index 5428cbf..c1cbdec 100644
--- a/pac-man-board-game/Services/GameGroup.cs
+++ b/pac-man-board-game/Services/GameGroup.cs
@@ -32,8 +32,11 @@ public class GameGroup // TODO tests
         return Players;
     }
 
-    public void SetAllInGame()
+    public bool SetAllInGame()
     {
+        if (Players.Any(player => player.State != State.Ready)) return false;
+
         foreach (var player in Players) player.State = State.InGame;
+        return true;
     }
 }