Added File Access check to MockFileStream

Author: roketworks

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

@@ -76,6 +76,46 @@ public void MockFileStream_Constructor_ReadTypeNotWritable()
             Assert.IsFalse(stream.CanWrite);
             Assert.Throws<NotSupportedException>(() => stream.WriteByte(1));
         }
+        
+        [Test]
+        [TestCase(FileShare.None, MockFileStream.StreamType.READ)]
+        [TestCase(FileShare.None, MockFileStream.StreamType.WRITE)]
+        [TestCase(FileShare.None, MockFileStream.StreamType.APPEND)]
+        [TestCase(FileShare.None, MockFileStream.StreamType.TRUNCATE)]
+        [TestCase(FileShare.Read, MockFileStream.StreamType.WRITE)]
+        [TestCase(FileShare.Read, MockFileStream.StreamType.APPEND)]
+        [TestCase(FileShare.Read, MockFileStream.StreamType.TRUNCATE)]
+        [TestCase(FileShare.Write, MockFileStream.StreamType.READ)]
+        public void MockFileStream_Constructor_Insufficient_FileShare_Throws_Exception(FileShare allowedFileShare, MockFileStream.StreamType streamType)
+        {
+            var filePath = @"C:\locked.txt";            
+            var fileSystem = new MockFileSystem(new Dictionary<string, MockFileData>
+            {
+                { filePath, new MockFileData("cannot access") { AllowedFileShare = allowedFileShare } }
+            });
+            
+            Assert.Throws<IOException>(() => new MockFileStream(fileSystem, filePath, streamType));
+        }
+        
+        [Test]
+        [TestCase(FileShare.Read, MockFileStream.StreamType.READ)]
+        [TestCase(FileShare.Read | FileShare.Write, MockFileStream.StreamType.READ)]
+        [TestCase(FileShare.Read | FileShare.Write, MockFileStream.StreamType.APPEND)]
+        [TestCase(FileShare.Read | FileShare.Write, MockFileStream.StreamType.TRUNCATE)]
+        [TestCase(FileShare.ReadWrite, MockFileStream.StreamType.READ)]
+        [TestCase(FileShare.ReadWrite, MockFileStream.StreamType.WRITE)]
+        [TestCase(FileShare.ReadWrite, MockFileStream.StreamType.APPEND)]
+        [TestCase(FileShare.ReadWrite, MockFileStream.StreamType.TRUNCATE)]
+        public void MockFileStream_Constructor_Sufficient_FileShare_Does_Not_Throw_Exception(FileShare allowedFileShare, MockFileStream.StreamType streamType)
+        {
+            var filePath = @"C:\locked.txt";       
+            var fileSystem = new MockFileSystem(new Dictionary<string, MockFileData>
+            {
+                { filePath, new MockFileData("cannot access") { AllowedFileShare = allowedFileShare } }
+            });
+            
+            Assert.DoesNotThrow(() => new MockFileStream(fileSystem, filePath, streamType));
+        }
 
         [Test]
         public void MockFileStream_Close_MultipleCallsDontThrow()

System.IO.Abstractions.TestingHelpers/MockFileStream.cs

@@ -39,11 +39,14 @@ public MockFileStream(
             this.mockFileDataAccessor = mockFileDataAccessor ?? throw new ArgumentNullException(nameof(mockFileDataAccessor));
             this.path = path;
             this.options = options;
-
+            
             if (mockFileDataAccessor.FileExists(path))
             {
+                var fileData = mockFileDataAccessor.GetFile(path);
+                fileData.CheckFileAccess(path, streamType != StreamType.READ ? FileAccess.Write : FileAccess.Read);
+                
                 /* only way to make an expandable MemoryStream that starts with a particular content */
-                var data = mockFileDataAccessor.GetFile(path).Contents;
+                var data = fileData.Contents;
                 if (data != null && data.Length > 0 && streamType != StreamType.TRUNCATE)
                 {
                     Write(data, 0, data.Length);
@@ -60,7 +63,7 @@ public MockFileStream(
                 }
                 mockFileDataAccessor.AddFile(path, new MockFileData(new byte[] { }));
             }
-
+            
             canWrite = streamType != StreamType.READ;
         }