fix: MockFileInfo.Exists no longer returns stale cached data

In 5216e0d ("fix: make Mock{File,Directory}Info cache file attributes
(TestableIO#791)", 2022-01-09) a cache of the MockFileData was introduced, to mimic
the behaviour that a FileInfo object will not read the data from disk
but instead also remembers its internal state, which can be updated by
calling its `Refresh` method. This internal (or cached state) is
invalidated when calling the methods `Create`, `Delete` and `MoveTo`
methods, as can be seen by the `Invalidate` calls in
https://github.com/dotnet/runtime/blob/8766a1cf1ed6c3b69cef50154139699b72fb52c5/src/libraries/System.Private.CoreLib/src/System/IO/FileInfo.cs

In the PR TestableIO#791 it was overlooked to also invalidate the cached data
in these methods. This commit fixes it by invalidating the cached data
only for `Create`, `CreateText` and `Delete`.

The two `MoveTo` variants are not changed as I could not manage to find
any behaviour which is broken without that invalidation.
Most likely reason is that the  MockFileData is updated to represent the
destination file ofter the move, so invalidating is not needed.

Fixes TestableIO#822

Author: siprbaum

src/System.IO.Abstractions.TestingHelpers/MockFileInfo.cs

@@ -28,6 +28,7 @@ public MockFileInfo(IMockFileDataAccessor mockFileSystem, string path) : base(mo
         /// <inheritdoc />
         public override void Delete()
         {
+            refreshOnNextRead = true;
             mockFile.Delete(path);
         }
 
@@ -221,13 +222,17 @@ public override IFileInfo CopyTo(string destFileName, bool overwrite)
         /// <inheritdoc />
         public override Stream Create()
         {
-            return mockFile.Create(FullName);
+            var result = mockFile.Create(FullName);
+            refreshOnNextRead = true;
+            return result;
         }
 
         /// <inheritdoc />
         public override StreamWriter CreateText()
         {
-            return mockFile.CreateText(FullName);
+            var result = mockFile.CreateText(FullName);
+            refreshOnNextRead = true;
+            return result;
         }
 
         /// <inheritdoc />

tests/System.IO.Abstractions.TestingHelpers.Tests/MockFileInfoTests.cs

@@ -750,6 +750,49 @@ public void MockFileInfo_Exists_ShouldUpdateCachedDataOnRefresh()
             Assert.IsTrue(fileInfo.Exists);
         }
 
+        [Test]
+        public void MockFileInfo_Create_ShouldUpdateCachedDataAndReturnTrueForExists()
+        {
+            IFileSystem fileSystem = new MockFileSystem();
+            var path = XFS.Path(@"c:\temp\file1.txt");
+            IFileInfo fileInfo = fileSystem.FileInfo.FromFileName(path);
+
+            // Act
+            fileInfo.Create().Dispose();
+
+            // Assert
+            var result = fileInfo.Exists;
+            Assert.IsTrue(result);
+        }
+
+        [Test]
+        public void MockFileInfo_CreateText_ShouldUpdateCachedDataAndReturnTrueForExists()
+        {
+            IFileSystem fileSystem = new MockFileSystem();
+            var path = XFS.Path(@"c:\temp\file1.txt");
+            IFileInfo fileInfo = fileSystem.FileInfo.FromFileName(path);
+
+            // Act
+            fileInfo.CreateText().Dispose();
+
+            // Assert
+            Assert.IsTrue(fileInfo.Exists);
+        }
+
+        [Test]
+        public void MockFileInfo_Delete_ShouldUpdateCachedDataAndReturnFalseForExists()
+        {
+            var fileSystem = new MockFileSystem();
+            var path = XFS.Path(@"c:\temp\file1.txt");
+            IFileInfo fileInfo = fileSystem.FileInfo.FromFileName(path);
+
+            // Act
+            fileInfo.Delete();
+
+            // Assert
+            Assert.IsFalse(fileInfo.Exists);
+        }
+
         [Test]
         public void MockFileInfo_Delete_ShouldThrowIfFileAccessShareHasNoWriteOrDeleteAccess()
         {