Add Common test helper classes for file cleanup

Later one we can consolidate to these with the ones used in other test projects (and have additional test projects use these to avoid leaving straggling test files behind).

Author: stephentoub

src/Common/tests/System/IO/FileCleanupTestBase.cs

@@ -0,0 +1,61 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.Runtime.CompilerServices;
+
+namespace System.IO
+{
+    /// <summary>Base class for test classes the use temporary files that need to be cleaned up.</summary>
+    public abstract class TemporaryFilesCleanupTestBase : IDisposable
+    {
+        /// <summary>Initialize the test class base.</summary>
+        protected TemporaryFilesCleanupTestBase()
+        {
+            // Use a unique test directory per test class
+            TestDirectory = Path.Combine(Path.GetTempPath(), GetType().Name + "_" + Guid.NewGuid().ToString("N"));
+            try
+            {
+                Directory.CreateDirectory(TestDirectory);
+            }
+            catch
+            {
+                // Don't throw exceptions during test class construction.  Attempts to use paths
+                // under this directory will instead appropriately fail later.
+            }
+        }
+
+        ~TemporaryFilesCleanupTestBase()
+        {
+            Dispose(false);
+        }
+
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        protected void Dispose(bool disposing)
+        {
+            // No managed resources to clean up.
+
+            try { Directory.Delete(TestDirectory, recursive: true); }
+            catch { } // avoid exceptions from Dispose
+        }
+
+        /// <summary>Gets the test directory into which all files and directories created by tests should be stored.</summary>
+        protected string TestDirectory { get; private set; }
+
+        /// <summary>Generates a test file full path that is unique to the call site.</summary>
+        protected string GetTestFilePath([CallerMemberName]string fileName = null, [CallerLineNumber] int lineNumber = 0)
+        {
+            return Path.Combine(TestDirectory, GetTestFileName(fileName, lineNumber));
+        }
+
+        /// <summary>Generates a test file name that is unique to the call site.</summary>
+        protected string GetTestFileName([CallerMemberName]string fileName = null, [CallerLineNumber] int lineNumber = 0)
+        {
+            return string.Format("{0}_{1}", fileName ?? "TestBase", lineNumber);
+        }
+    }
+}

src/Common/tests/System/IO/TempFile.cs

@@ -0,0 +1,41 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace System.IO
+{
+    /// <summary>
+    /// Represents a temporary file.  Creating an instance creates a file at the specified path,
+    /// and disposing the instance deletes the file.
+    /// </summary>
+    public sealed class TempFile : IDisposable
+    {
+        /// <summary>Gets the created file's path.</summary>
+        public string Path { get; private set; }
+
+        public TempFile(string path, long length = 0)
+        {
+            Path = path;
+            using (FileStream fs = File.Create(path))
+            {
+                if (length > 0)
+                {
+                    // Fill with zeros up to the desired length.
+                    fs.Write(new byte[length], 0, (int)length);
+                }
+            }
+        }
+
+        ~TempFile() { DeleteFile(); }
+
+        public void Dispose()
+        {
+            GC.SuppressFinalize(this);
+            DeleteFile();
+        }
+
+        private void DeleteFile()
+        {
+            File.Delete(Path);
+        }
+    }
+}