Update conversion

BritishHorseRacingApi.Tests/DataConverterHelperTests.cs

@@ -35,6 +35,19 @@ namespace BritishHorseRacingApi.Tests
             Assert.Equal(totalMilliseconds, expectedValue);
         }
 
+        [Theory()]
+        [InlineData("1m 15.39s(+0.34s)", 340)]
+        [InlineData(null, null)]
+        [InlineData(" ", null)]
+        public void TestStopwatchStringDifferenceToMilliseconds(string time, double? expectedValue)
+        {
+            //Arrange
+            //Act
+            var totalMilliseconds = DataConverterHelper.StopwatchStringDifferenceToMilliseconds(time);
+            //Assert
+            Assert.Equal(totalMilliseconds, expectedValue);
+        }
+
         [Theory()]
         [InlineData("1m 1f 104y ", 2084)]
         [InlineData("1f 104y", 324)]

BritishHorseRacingApi/Helpers/DataConverterHelper.cs

@@ -58,10 +58,13 @@ namespace BritishHorseRacingApi.Helpers
             return (T)Convert.ChangeType(group.Value, typeof(T));
         }
 
-        public static int StopwatchStringDifferenceToMilliseconds(string timeDifferenceString)
+        public static int? StopwatchStringDifferenceToMilliseconds(string timeDifferenceString)
         {
+            if (String.IsNullOrWhiteSpace(timeDifferenceString))
+                return null;
+
             var match = _stopwatchTimeRegex.Match(timeDifferenceString);
-            var lossDifference = GetComponent(match, "lossDifference", 0);
+            var lossDifference = GetComponent(match, "lossDifference", 0d);
             return (int)TimeSpan.FromSeconds(lossDifference).TotalMilliseconds;
         }
     }