[release/6.0] Make tests for FileLoggerProcessor system time independent (#42115)

* Fix conflicts

* Fixup

* Fixup

* Update src/Middleware/HttpLogging/test/FileLoggerProcessorTests.cs

Co-authored-by: Benedikt <benedikt.achatz@gmail.com>
Co-authored-by: Doug Bunting <6431421+dougbu@users.noreply.github.com>

src/Middleware/HttpLogging/src/FileLoggerProcessor.cs

@@ -30,7 +30,7 @@ namespace Microsoft.AspNetCore.HttpLogging
         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 @@ namespace Microsoft.AspNetCore.HttpLogging
         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 @@ namespace Microsoft.AspNetCore.HttpLogging
                 }
             });
 
+            _today = SystemDateTime.Now;
+
             // Start message queue processor
             _cancellationTokenSource = new CancellationTokenSource();
             _outputTask = Task.Run(ProcessLogQueue);
@@ -155,7 +160,7 @@ namespace Microsoft.AspNetCore.HttpLogging
         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;
 
             if (!TryCreateDirectory())
             {

src/Middleware/HttpLogging/src/ISystemDateTime.cs

+// 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 interface ISystemDateTime
+    {
+        /// <summary> 
+        /// Retrieves the date and time currently set for this machine.
+        /// </summary> 
+        DateTime Now { get; }
+    }
+}

src/Middleware/HttpLogging/src/SystemDateTime.cs

+// 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;
+    }
+}

src/Middleware/HttpLogging/test/MockSystemDateTime.cs

+// 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 MockSystemDateTime : ISystemDateTime
+    {
+        public DateTime Now { get; set; }
+    }
+}