fix(runner): handle negative iteration index in getIterationData

lib/runner/util.js

@@ -315,12 +315,18 @@ module.exports = {
      * @return {Any} - The data for the iteration
      */
     getIterationData (data, iteration) {
-    // if iteration has a corresponding data element use that
+        if (!Array.isArray(data) || !data.length) {
+        return;
+        }
+
+        if (iteration < 0) {
+            return data[0];
+        }
+
         if (iteration < data.length) {
             return data[iteration];
         }
 
-        // otherwise use the last data element
         return data[data.length - 1];
     },
 

test/unit/runner-util.test.js

@@ -131,6 +131,16 @@ describe('runner util', function () {
     });
 
     describe('.getIterationData', function () {
+        it('should handle negative iteration index', function () {
+            var data = [
+                    { value: 'first' },
+                    { value: 'second' }
+                ],
+                result = runnerUtil.getIterationData(data, -1);
+
+            expect(result).to.equal(data[0]);
+        });
+
         it('should return data for the specified iteration', function () {
             var data = [
                     { iteration: 0, value: 'first' },