Add some more tests detecting potential multiple transitions

Author: leeoades

FunctionalStateMachine.Core.Tests/StateMachineAnalysisTests.cs

@@ -257,6 +257,64 @@ public void Validate_DetectsMultipleTransitionToInSameTransition()
         Assert.Contains("TransitionTo", exception.Message, StringComparison.OrdinalIgnoreCase);
     }
 
+    [Fact]
+    public void Validate_DetectsTransitionToAfterConditionalChain()
+    {
+        var exception = Assert.Throws<InvalidOperationException>(() =>
+        {
+            var machine = StateMachine<State, Trigger, Data, CommandBase>.Create()
+                .StartWith(State.A)
+                .For(State.A)
+                    .On<Trigger.T1>()
+                        .If(data => data.Value > 5)
+                            .TransitionTo(State.B)
+                            .Else()
+                            .Execute(() => new Command.Noop())
+                            .Done()
+                        .TransitionTo(State.C)
+                .For(State.B)
+                    .On<Trigger.T1>()
+                        .TransitionTo(State.A)
+                .For(State.C)
+                    .On<Trigger.T1>()
+                        .TransitionTo(State.A)
+                .Build();
+        });
+
+        Assert.Contains("TransitionTo", exception.Message, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public void Validate_DetectsTransitionToInTwoConditionalChains()
+    {
+        var exception = Assert.Throws<InvalidOperationException>(() =>
+        {
+            var machine = StateMachine<State, Trigger, Data, CommandBase>.Create()
+                .StartWith(State.A)
+                .For(State.A)
+                    .On<Trigger.T1>()
+                        .If(data => data.Value > 5)
+                            .TransitionTo(State.B)
+                            .Else()
+                            .Execute(() => new Command.Noop())
+                            .Done()
+                        .If(data => data.Value > 1)
+                            .TransitionTo(State.C)
+                            .Else()
+                            .Execute(() => new Command.Noop())
+                            .Done()
+                .For(State.B)
+                    .On<Trigger.T1>()
+                        .TransitionTo(State.A)
+                .For(State.C)
+                    .On<Trigger.T1>()
+                        .TransitionTo(State.A)
+                .Build();
+        });
+
+        Assert.Contains("TransitionTo", exception.Message, StringComparison.OrdinalIgnoreCase);
+    }
+
     [Fact]
     public void Validate_AllowsComplexReachableStateMachine()
     {

docs/conditional-steps.md

@@ -78,6 +78,28 @@ var machine = StateMachine<State, Trigger, Data, Command>.Create()
 
 With multiple ElseIf conditions, only the first matching branch executes. If no condition matches and there's no Else, nothing happens.
 
+## Multiple conditional chains with TransitionTo
+
+If you use multiple conditional chains within the same transition, only one chain may contain a TransitionTo.
+
+```csharp
+var machine = StateMachine<State, Trigger, Data, Command>.Create()
+    .StartWith(State.Pending)
+    .For(State.Pending)
+        .On<Trigger.Submit>()
+            .If(data => data.IsValid)
+                .TransitionTo(State.Approved)
+                .Else()
+                .Execute(() => new Command.LogRejected())
+                .Done()
+            .If(data => data.IsHighPriority)
+                .TransitionTo(State.Escalated) // ❌ second TransitionTo in same transition
+                .Else()
+                .Execute(() => new Command.LogPriority())
+                .Done()
+    .Build();
+```
+
 ## Using with ModifyData
 
 Conditional data modifications work seamlessly: