Add test

Author: Marcin_Osada

test/Serilog.Sinks.File.Tests/RollingFileSinkTests.cs

@@ -71,6 +71,28 @@ public void WhenRetentionCountIsSetOldFilesAreDeleted()
                 });
         }
 
+        [Fact]
+        public void WhenRetentionCountAndArchivingHookIsSetOldFilesAreCopiedAndOriginalDeleted()
+        {
+            const string archiveDirectory = "OldLogs";
+            LogEvent e1 = Some.InformationEvent(),
+                    e2 = Some.InformationEvent(e1.Timestamp.AddDays(1)),
+                    e3 = Some.InformationEvent(e2.Timestamp.AddDays(5));
+
+            TestRollingEventSequence(
+                (pf, wt) => wt.File(pf, retainedFileCountLimit: 2, rollingInterval: RollingInterval.Day, hooks: new ArchiveOldLogsHook(archiveDirectory)),
+                new[] {e1, e2, e3},
+                files =>
+                {
+                    Assert.Equal(3, files.Count);
+                    Assert.True(!System.IO.File.Exists(files[0]));
+                    Assert.True(System.IO.File.Exists(files[1]));
+                    Assert.True(System.IO.File.Exists(files[2]));
+
+                    Assert.True(System.IO.File.Exists(ArchiveOldLogsHook.AddTopDirectory(files[0], archiveDirectory)));
+                });
+        }
+
         [Fact]
         public void WhenSizeLimitIsBreachedNewFilesCreated()
         {

test/Serilog.Sinks.File.Tests/Support/ArchiveOldLogsHook.cs

@@ -0,0 +1,35 @@
+using System;
+using System.IO;
+using System.Text;
+
+namespace Serilog.Sinks.File.Tests.Support
+{
+    internal class ArchiveOldLogsHook : FileLifecycleHooks
+    {
+        private readonly string _relativeArchiveDir;
+
+        public ArchiveOldLogsHook(string relativeArchiveDir)
+        {
+            _relativeArchiveDir = relativeArchiveDir;
+        }
+
+        public override void OnFileDeleting(string path)
+        {
+            base.OnFileDeleting(path);
+            var newFile = AddTopDirectory(path, _relativeArchiveDir, true);
+            System.IO.File.Copy(path, newFile, false);
+        }
+
+        public static string AddTopDirectory(string path, string directoryToAdd, bool createOnNonExist = false)
+        {
+            string file = Path.GetFileName(path);
+            string directory = Path.Combine(Path.GetDirectoryName(path) ?? throw new InvalidOperationException(), directoryToAdd);
+
+            if (createOnNonExist && !Directory.Exists(directory))
+            {
+                Directory.CreateDirectory(directory);
+            }
+            return Path.Combine(directory, file);
+        }
+    }
+}