feat: set Creation, LastAccess and LastWrite time for files

src/System.IO.Abstractions.TestingHelpers/MockFile.cs

@@ -542,7 +542,7 @@ private Stream OpenInternal(
             var mockFileData = mockFileDataAccessor.GetFile(path);
             mockFileData.CheckFileAccess(path, access);
             var timeAdjustments = TimeAdjustments.LastAccessTime;
-            if (access != FileAccess.Read)
+            if (access.HasFlag(FileAccess.Write))
             {
                 timeAdjustments |= TimeAdjustments.LastWriteTime;
             }

src/System.IO.Abstractions.TestingHelpers/MockFileData.cs

@@ -49,7 +49,10 @@ public class MockFileData
         /// </summary>
         private MockFileData()
         {
-            // empty
+            var now = DateTime.UtcNow;
+            LastWriteTime = now;
+            LastAccessTime = now;
+            CreationTime = now;
         }
 
         /// <summary>

src/System.IO.Abstractions.TestingHelpers/MockFileStream.cs

@@ -34,7 +34,8 @@ public MockFileStream(
                 fileData = mockFileDataAccessor.GetFile(path);
                 fileData.CheckFileAccess(path, access);
 
-                mockFileDataAccessor.AdjustTimes(fileData, TimeAdjustments.LastAccessTime);
+                var timeAdjustments = GetTimeAdjustmentsForFileStreamWhenFileExists(mode, access);
+                mockFileDataAccessor.AdjustTimes(fileData, timeAdjustments);
                 var existingContents = fileData.Contents;
                 var keepExistingContents =
                     existingContents?.Length > 0 &&
@@ -140,5 +141,30 @@ private void OnClose()
                 mockFileDataAccessor.FileInfo.FromFileName(path).Encrypt();
             }
         }
+
+        private TimeAdjustments GetTimeAdjustmentsForFileStreamWhenFileExists(FileMode mode, FileAccess access)
+        {
+            switch (mode)
+            {
+                case FileMode.Append:
+                case FileMode.CreateNew:
+                    if (access.HasFlag(FileAccess.Read))
+                    {
+                        return TimeAdjustments.LastAccessTime;
+                    }
+                    return TimeAdjustments.None;
+                case FileMode.Create:
+                case FileMode.Truncate:
+                    if (access.HasFlag(FileAccess.Write))
+                    {
+                        return TimeAdjustments.LastAccessTime | TimeAdjustments.LastWriteTime;
+                    }
+                    return TimeAdjustments.LastAccessTime;
+                case FileMode.Open:
+                case FileMode.OpenOrCreate:
+                default:
+                    return TimeAdjustments.None;
+            }
+        }
     }
 }