Improvements to If unit tests

test/unit/Elsa.Activities.UnitTests/Branching/IfTests.cs

@@ -1,6 +1,7 @@
 using Elsa.Extensions;
 using Elsa.Testing.Shared;
 using Elsa.Workflows;
+using Elsa.Workflows.Exceptions;
 
 namespace Elsa.Activities.UnitTests.Branching;
 
@@ -167,6 +168,145 @@ public class IfTests
         Assert.True(resultValue);
         Assert.False(context.HasScheduledActivity(elseActivity), "Else branch should not be scheduled when condition is true");
     }
+    
+    [Fact]
+    public async Task Should_Not_Throw_Error_When_Condition_Is_Not_Set()
+    {
+        // Arrange
+        var ifActivity = new If(); // no condition provided
+        var thenActivity = new WriteLine("then");
+        ifActivity.Then = thenActivity;
+
+        // Act
+        var context = await ExecuteAsync(ifActivity);
+        
+        // Assert
+        Assert.NotNull(context);
+    }
+    
+    [Fact]
+    public async Task Should_Bubble_Exception_From_Condition_And_Not_Schedule_Any_Branch()
+    {
+        // Arrange
+        var ifActivity = new If(() =>  throw new ApplicationException("boom"));
+        var thenActivity = new WriteLine("then");
+        var elseActivity = new WriteLine("else");
+        ifActivity.Then = thenActivity;
+        ifActivity.Else = elseActivity;
+
+        // Act - Throwing any kind of exception in the condition results in an InputEvaluationException
+        var ex = await Assert.ThrowsAsync<InputEvaluationException>(() => ExecuteAsync(ifActivity));
+
+        // Assert
+        Assert.Contains("Failed to evaluate", ex.Message);
+    }
+    
+    [Fact]
+    public async Task Should_Evaluate_Condition_Exactly_Once()
+    {
+        // Arrange
+        var count = 0;
+        var ifActivity = new If(() => { count++; return true; });
+        var thenActivity = new WriteLine("then");
+        ifActivity.Then = thenActivity;
+
+        // Act
+        var context = await ExecuteAsync(ifActivity);
+
+        // Assert
+        Assert.Equal(1, count);
+        Assert.True(context.HasScheduledActivity(thenActivity));
+    }
+    
+    [Fact]
+    public async Task Should_Use_Latest_Captured_State_When_Evaluating_Condition()
+    {
+        // Arrange
+        var flag = false;
+        // ReSharper disable once AccessToModifiedClosure
+        var ifActivity = new If(() => flag);
+        var thenActivity = new WriteLine("then");
+        var elseActivity = new WriteLine("else");
+        ifActivity.Then = thenActivity;
+        ifActivity.Else = elseActivity;
+
+        // Mutate after construction, before execution
+        flag = true;
+
+        // Act
+        var context = await ExecuteAsync(ifActivity);
+
+        // Assert
+        var resultValue = (bool)context.GetActivityOutput(() => ifActivity.Result)!;
+        Assert.True(resultValue);
+        Assert.True(context.HasScheduledActivity(thenActivity));
+        Assert.False(context.HasScheduledActivity(elseActivity));
+    }
+    
+    [Theory]           // outer, inner
+    [InlineData(true,  true)]
+    [InlineData(true,  false)]
+    [InlineData(false, true)]
+    [InlineData(false, false)]
+    public async Task Should_Schedule_Correct_Branches_For_Nested_If(bool outerCondition, bool innerCondition)
+    {
+        // Arrange inner
+        var innerThen = new WriteLine("inner-then");
+        var innerElse = new WriteLine("inner-else");
+        var innerIf = new If(() => innerCondition)
+        {
+            Then = innerThen,
+            Else = innerElse
+        };
+
+        // Arrange outer
+        var outerElse = new WriteLine("outer-else");
+        var outerIf = new If(() => outerCondition)
+        {
+            Then = innerIf,
+            Else = outerElse
+        };
+
+        // Act
+        var context = await ExecuteAsync(outerIf);
+
+        // Assert outer result & scheduling
+        var outerResult = (bool)context.GetActivityOutput(() => outerIf.Result)!;
+        Assert.Equal(outerCondition, outerResult);
+
+        if (outerCondition)
+        {
+            // When outer condition is true, the inner If should be scheduled
+            Assert.True(context.HasScheduledActivity(innerIf), 
+                "Inner If should be scheduled when outer condition is true");
+            
+            // The outer else should NOT be scheduled
+            Assert.False(context.HasScheduledActivity(outerElse), 
+                "Outer else should not be scheduled when outer condition is true");
+            
+            // The inner branches should NOT be scheduled yet because the inner If hasn't executed
+            Assert.False(context.HasScheduledActivity(innerThen), 
+                "Inner then should not be scheduled yet - inner If hasn't executed");
+            Assert.False(context.HasScheduledActivity(innerElse), 
+                "Inner else should not be scheduled yet - inner If hasn't executed");
+            
+            // Note: The inner If result won't be available until it executes, so we can't assert it
+        }
+        else
+        {
+            // When outer condition is false, outer else should be scheduled
+            Assert.True(context.HasScheduledActivity(outerElse), 
+                "Outer else should be scheduled when outer condition is false");
+            
+            // The inner If and its branches should NOT be scheduled
+            Assert.False(context.HasScheduledActivity(innerIf), 
+                "Inner If should not be scheduled when outer condition is false");
+            Assert.False(context.HasScheduledActivity(innerThen), 
+                "Inner then should not be scheduled when outer condition is false");
+            Assert.False(context.HasScheduledActivity(innerElse), 
+                "Inner else should not be scheduled when outer condition is false");
+        }
+    }
 
     private static Task<ActivityExecutionContext> ExecuteAsync(IActivity activity)
     {