Stop calling real IO.Path.GetTempPath() when creating a MockFileSystem (#372)

* Stop calling real IO.Path.GetTempPath() when creating a MockFileSystem

* Ensure current directory of MockFileSystem exists on creation

* fix failing test on linux

Fixes #350

Author: tehmantra

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

@@ -1184,11 +1184,12 @@ public void MockDirectory_GetCurrentDirectory_ShouldReturnValueFromFileSystemCon
 
             Assert.AreEqual(directory, actual);
         }
-
-
+        
         [Test]
-        public void MockDirectory_GetCurrentDirectory_ShouldReturnDefaultPathWhenNotSet() {
-            string directory = Path.GetTempPath();
+        public void MockDirectory_GetCurrentDirectory_ShouldReturnDefaultPathWhenNotSet() 
+        {
+            string directory = XFS.Path(@"C:\");
+
             var fileSystem = new MockFileSystem();
 
             var actual = fileSystem.Directory.GetCurrentDirectory();

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

@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
 using System.Text;
@@ -292,5 +292,17 @@ public void MockFileSystem_GetFiles_ThrowsArgumentExceptionForInvalidCharacters(
             // Assert
             Assert.Throws<ArgumentException>(getFilesWithInvalidCharacterInPath);
         }
+
+        [Test]
+        [TestCase(null)]
+        [TestCase(@"C:\somepath")]
+        public void MockFileSystem_DefaultState_CurrentDirectoryExists(string currentDirectory)
+        {
+            var fs = new MockFileSystem(null, currentDirectory);
+
+            var actualCurrentDirectory = fs.DirectoryInfo.FromDirectoryName(".");
+
+            Assert.IsTrue(actualCurrentDirectory.Exists);
+        }
     }
 }

System.IO.Abstractions.TestingHelpers/MockFileSystem.cs

@@ -9,6 +9,8 @@ namespace System.IO.Abstractions.TestingHelpers
     [Serializable]
     public class MockFileSystem : IFileSystem, IMockFileDataAccessor
     {
+        private const string DEFAULT_CURRENT_DIRECTORY = @"C:\";
+
         private readonly IDictionary<string, MockFileData> files;
         [NonSerialized]
         private readonly PathVerifier pathVerifier;
@@ -19,7 +21,7 @@ public MockFileSystem(IDictionary<string, MockFileData> files, string currentDir
         {
             if (string.IsNullOrEmpty(currentDirectory))
             {
-                currentDirectory = IO.Path.GetTempPath();
+                currentDirectory = XFS.Path(DEFAULT_CURRENT_DIRECTORY);
             }
 
             pathVerifier = new PathVerifier(this);
@@ -42,6 +44,11 @@ public MockFileSystem(IDictionary<string, MockFileData> files, string currentDir
                     AddFile(entry.Key, entry.Value);
                 }
             }
+
+            if (!FileExists(currentDirectory))
+            {
+                AddDirectory(currentDirectory);
+            }
         }
 
         public FileBase File { get; }