Fixes and missing tests

Author: LeeCampbell

src/HdrHistogram.UnitTests/HistogramTestBase.cs

@@ -1,4 +1,6 @@
 using System;
+using System.IO;
+using System.Threading;
 using NUnit.Framework;
 
 namespace HdrHistogram.UnitTests
@@ -21,7 +23,7 @@ public void ConstructorShouldRejectInvalidParameters(
             Assert.AreEqual(errorParamName, ex.ParamName);
             StringAssert.StartsWith(errorMessage, ex.Message);
         }
-        
+
 
         [TestCase(2, 2)]
         [TestCase(HighestTrackableValue, NumberOfSignificantValueDigits)]
@@ -123,6 +125,23 @@ public void RecordAction_increments_TotalCount()
             Assert.AreEqual(1, longHistogram.TotalCount);
         }
 
+        [Test]
+        public void RecordAction_records_in_correct_units()
+        {
+            var pause = TimeSpan.FromSeconds(1);
+            var longHistogram = Create(HighestTrackableValue, NumberOfSignificantValueDigits);
+
+            longHistogram.Record(() => Thread.Sleep(pause));
+
+            var stringWriter = new StringWriter();
+            longHistogram.OutputPercentileDistribution(stringWriter, 5, OutputScalingFactor.TimeStampToMilliseconds, true);
+            //First column of second row.
+            var recordedMilliseconds = GetCellValue(stringWriter.ToString(), 0, 1);
+            var actual = double.Parse(recordedMilliseconds);
+            var expected = pause.TotalMilliseconds;
+            var delta = expected * 0.1;   //10% Variance to allow for slack in transitioning from Thread.Sleep
+            Assert.AreEqual(expected, actual, delta);
+        }
 
         [Test]
         public void Reset_sets_counts_to_zero()
@@ -265,5 +284,10 @@ private static int GetBucketsNeededToCoverValue(int subBucketSize, long value)
         protected abstract int WordSize { get; }
         protected abstract HistogramBase Create(long highestTrackableValue, int numberOfSignificantValueDigits);
         protected abstract HistogramBase Create(long lowestTrackableValue, long highestTrackableValue, int numberOfSignificantValueDigits);
+
+        private static string GetCellValue(string csvData, int col, int row)
+        {
+            return csvData.Split('\n')[row].Split(',')[col];
+        }
     }
 }

src/HdrHistogram/HistogramExtensions.cs

@@ -72,7 +72,18 @@ public static long HighestEquivalentValue(this HistogramBase histogram, long val
             return histogram.NextNonEquivalentValue(value) - 1;
         }
 
-
+        /// <summary>
+        /// Copy this histogram into the target histogram, overwriting it's contents.
+        /// </summary>
+        /// <param name="source">The source histogram</param>
+        /// <param name="targetHistogram">the histogram to copy into</param>
+        public static void CopyInto(this HistogramBase source, HistogramBase targetHistogram)
+        {
+            targetHistogram.Reset();
+            targetHistogram.Add(source);
+            targetHistogram.StartTimeStamp = source.StartTimeStamp;
+            targetHistogram.EndTimeStamp = source.EndTimeStamp;
+        }
 
         /// <summary>
         /// Provide a means of iterating through histogram values according to percentile levels. 
@@ -193,7 +204,7 @@ public static void Record(this IRecorder recorder, Action action)
             var start = Stopwatch.GetTimestamp();
             action();
             var elapsed = Stopwatch.GetTimestamp() - start;
-            histogram.RecordValue(elapsed);
+            recorder.RecordValue(elapsed);
         }
     }
 }