Ensure temp directory in MockFileSystem exists

Fixes #588 

Co-authored-by: Iris Classon <iris@greenbyte.com>

Author: IrisClasson

System.IO.Abstractions.TestingHelpers.Tests/MockFileSystemTests.cs

@@ -292,7 +292,8 @@ public void MockFileSystem_AllNodes_ShouldReturnAllNodes()
                 XFS.Path(@"c:\something\demo.txt"),
                 XFS.Path(@"c:\something\other.gif"),
                 XFS.Path(@"d:\foobar"),
-                XFS.Path(@"d:\foo\bar")
+                XFS.Path(@"d:\foo\bar"),
+                XFS.Path(@"C:\temp")
             };
 
             var result = fileSystem.AllNodes;
@@ -340,6 +341,18 @@ public void MockFileSystem_DefaultState_CurrentDirectoryExists(string currentDir
             Assert.IsTrue(actualCurrentDirectory.Exists);
         }
 
+        [Test]
+        public void MockFileSystem_DefaultState_DefaultTempDirectoryExists()
+        {
+            var tempDirectory = XFS.Path(@"C:\temp");
+
+            var mockFileSystem = new MockFileSystem();
+            var mockFileSystemOverload = new MockFileSystem(null, string.Empty);
+            
+            Assert.IsTrue(mockFileSystem.Directory.Exists(tempDirectory));
+            Assert.IsTrue(mockFileSystemOverload.Directory.Exists(tempDirectory));
+        }
+
         [Test]
         public void MockFileSystem_FileSystemWatcher_PathShouldBeAssignable()
         {

System.IO.Abstractions.TestingHelpers.Tests/MockPathTests.cs

@@ -372,6 +372,49 @@ public void GetTempPath_Called_ReturnsStringLengthGreaterThanZero()
             Assert.IsTrue(result.Length > 0);
         }
 
+        [Test]
+        [TestCase(null)]
+        [TestCase("")]
+        [TestCase(@"C:\temp")]
+        public void GetTempPath_Called_ReturnsStringLengthGreaterThanZero(string tempDirectory) {
+            //Arrange
+            var mockPath = new MockPath(new MockFileSystem(), string.IsNullOrEmpty(tempDirectory)? tempDirectory: XFS.Path(tempDirectory));
+
+            //Act
+            var result = mockPath.GetTempPath();
+
+            //Assert
+            Assert.IsTrue(result.Length > 0);
+        }
+
+        [Test]
+        public void GetTempPath_Called_WithNonNullVirtualTempDirectory_ReturnsVirtualTempDirectory() {
+            //Arrange
+            var tempDirectory = XFS.Path(@"C:\temp");
+
+            var mockPath = new MockPath(new MockFileSystem(), tempDirectory);
+
+            //Act
+            var result = mockPath.GetTempPath();
+
+            //Assert
+            Assert.AreEqual(tempDirectory,result);
+        }
+
+        [Test]
+        [TestCase(null)]
+        [TestCase("")]
+        public void GetTempPath_Called_WithNullOrEmptyVirtualTempDirectory_ReturnsFallbackTempDirectory(string tempDirectory) {
+            //Arrange
+            var mockPath = new MockPath(new MockFileSystem(), tempDirectory);
+
+            //Act
+            var result = mockPath.GetTempPath();
+
+            //Assert
+            Assert.IsTrue(result.Length > 0);
+        }
+
         [Test]
         public void HasExtension_PathSentIn_DeterminesExtension()
         {

System.IO.Abstractions.TestingHelpers/MockFileSystem.cs

@@ -11,6 +11,7 @@ namespace System.IO.Abstractions.TestingHelpers
     public class MockFileSystem : IFileSystem, IMockFileDataAccessor
     {
         private const string DEFAULT_CURRENT_DIRECTORY = @"C:\";
+        private const string TEMP_DIRECTORY = @"C:\temp";
 
         private readonly IDictionary<string, MockFileData> files;
         private readonly PathVerifier pathVerifier;
@@ -24,11 +25,13 @@ public MockFileSystem(IDictionary<string, MockFileData> files, string currentDir
                 currentDirectory = XFS.Path(DEFAULT_CURRENT_DIRECTORY);
             }
 
+            var defaultTempDirectory = XFS.Path(TEMP_DIRECTORY);
+
             StringOperations = new StringOperations(XFS.IsUnixPlatform());
             pathVerifier = new PathVerifier(this);
             this.files = new Dictionary<string, MockFileData>(StringOperations.Comparer);
 
-            Path = new MockPath(this);
+            Path = new MockPath(this,defaultTempDirectory);
             File = new MockFile(this);
             Directory = new MockDirectory(this, currentDirectory);
             FileInfo = new MockFileInfoFactory(this);
@@ -49,6 +52,11 @@ public MockFileSystem(IDictionary<string, MockFileData> files, string currentDir
             {
                 AddDirectory(currentDirectory);
             }
+
+            if (!FileExists(defaultTempDirectory)) 
+            {
+                AddDirectory(defaultTempDirectory);
+            }
         }
 
         public StringOperations StringOperations { get; }

System.IO.Abstractions.TestingHelpers/MockPath.cs

@@ -11,10 +11,14 @@ namespace System.IO.Abstractions.TestingHelpers
     public class MockPath : PathWrapper
     {
         private readonly IMockFileDataAccessor mockFileDataAccessor;
+        private readonly string defaultTempDirectory;
 
-        public MockPath(IMockFileDataAccessor mockFileDataAccessor) : base(mockFileDataAccessor?.FileSystem)
+        public MockPath(IMockFileDataAccessor mockFileDataAccessor) : this(mockFileDataAccessor,string.Empty) { }
+
+        public MockPath(IMockFileDataAccessor mockFileDataAccessor,string defaultTempDirectory) : base(mockFileDataAccessor?.FileSystem)
         {
             this.mockFileDataAccessor = mockFileDataAccessor ?? throw new ArgumentNullException(nameof(mockFileDataAccessor));
+            this.defaultTempDirectory = !string.IsNullOrEmpty(defaultTempDirectory) ? defaultTempDirectory : base.GetTempPath();
         }
 
         public override string GetFullPath(string path)
@@ -128,13 +132,15 @@ private string[] GetSegments(params string[] paths)
         public override string GetTempFileName()
         {
             string fileName = mockFileDataAccessor.Path.GetRandomFileName();
-            string tempDir = mockFileDataAccessor.Path.GetTempPath();
+            string tempDir = this.GetTempPath();
 
             string fullPath = mockFileDataAccessor.Path.Combine(tempDir, fileName);
 
             mockFileDataAccessor.AddFile(fullPath, new MockFileData(string.Empty));
 
             return fullPath;
         }
+
+        public override string GetTempPath() => defaultTempDirectory;
     }
-}
+}