Make FileLoggerProcessTests systemtime independent

Author: benedikt257

src/Middleware/HttpLogging/src/FileLoggerProcessor.cs

@@ -30,7 +30,7 @@ internal partial class FileLoggerProcessor : IAsyncDisposable
         private bool _maxFilesReached;
         private TimeSpan _flushInterval;
         private W3CLoggingFields _fields;
-        private DateTime _today = DateTime.Now;
+        private DateTime _today;
         private bool _firstFile = true;
 
         private readonly IOptionsMonitor<W3CLoggerOptions> _options;
@@ -40,6 +40,9 @@ internal partial class FileLoggerProcessor : IAsyncDisposable
         private readonly Task _outputTask;
         private readonly CancellationTokenSource _cancellationTokenSource;
 
+        // Internal to allow for testing
+        internal ISystemDateTime SystemDateTime {get; set;} = new SystemDateTime();
+
         private readonly object _pathLock = new object();
 
         public FileLoggerProcessor(IOptionsMonitor<W3CLoggerOptions> options, IHostEnvironment environment, ILoggerFactory factory)
@@ -98,6 +101,8 @@ public FileLoggerProcessor(IOptionsMonitor<W3CLoggerOptions> options, IHostEnvir
                 }
             });
 
+            _today = SystemDateTime.Now;
+
             // Start message queue processor
             _cancellationTokenSource = new CancellationTokenSource();
             _outputTask = Task.Run(ProcessLogQueue);
@@ -155,7 +160,7 @@ private async Task ProcessLogQueue()
         private async Task WriteMessagesAsync(List<string> messages, CancellationToken cancellationToken)
         {
             // Files are written up to _maxFileSize before rolling to a new file
-            DateTime today = DateTime.Now;
+            DateTime today = SystemDateTime.Now;
             var fullName = GetFullName(today);
             // Don't write to an incomplete file left around by a previous FileLoggerProcessor
             if (_firstFile)

src/Middleware/HttpLogging/src/ISystemDateTime.cs

@@ -0,0 +1,6 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+internal interface ISystemDateTime {
+    DateTime Now { get; }
+}

src/Middleware/HttpLogging/src/SystemDateTime.cs

@@ -0,0 +1,10 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.AspNetCore.HttpLogging
+{
+    internal class SystemDateTime : ISystemDateTime
+    {
+        public DateTime Now => DateTime.Now;
+    }
+}