NoSuchTrialException when accessing trials that do not exist

Author: jackbrookes

Assets/UXF/Scripts/Session.cs

@@ -618,8 +618,17 @@ Trial GetPrevTrial()
         /// </summary>
         /// <returns></returns>
         Trial GetFirstTrial()
-        {
-            var firstBlock = blocks[0];
+        {   
+            Block firstBlock;
+            try
+            {
+                firstBlock = blocks[0];
+            }
+            catch (ArgumentOutOfRangeException)
+            {
+                throw new NoSuchTrialException("There is no first trial because no blocks have been created!");
+            }
+
             try
             {
                 return firstBlock.trials[0];
@@ -636,7 +645,16 @@ Trial GetFirstTrial()
         /// <returns></returns>
         Trial GetLastTrial()
         {
-            var lastBlock = blocks[blocks.Count - 1];
+            Block lastBlock;
+            try
+            {
+                lastBlock = blocks[0];
+            }
+            catch (ArgumentOutOfRangeException)
+            {
+                throw new NoSuchTrialException("There is no last trial because no blocks have been created!");
+            }
+            
             try
             {
                 return lastBlock.trials[lastBlock.trials.Count - 1];

Assets/UXF/Scripts/Tests/Editor/TestSessionBuilding.cs

@@ -129,6 +129,35 @@ public void SwapTrials()
             session.blocks = new List<Block>();
 
 		}
+
+		[Test]
+		public void InvalidTrialAccess()
+		{
+			Block block = session.CreateBlock();
+
+			Assert.Throws<NoSuchTrialException>(
+				delegate { Trial t = session.FirstTrial; }
+			);
+
+			Assert.Throws<NoSuchTrialException>(
+				delegate { Trial t = session.LastTrial; }
+			);
+
+			// reset blocks
+            session.blocks = new List<Block>();
+		}
+
+		[Test]
+		public void InvalidBlockAccess()
+		{
+			Assert.Throws<NoSuchTrialException>(
+				delegate { Trial t = session.FirstTrial; }
+			);
+
+			Assert.Throws<NoSuchTrialException>(
+				delegate { Trial t = session.LastTrial; }
+			);
+		}
 
 	}