Statistics
MockFileSystem.Statistics records every call made through the mock - which property was accessed, which method was invoked, with what arguments. Use it to assert what a system under test did, not just what it produced.
MockFileSystem fileSystem = new();
fileSystem.File.WriteAllText("a.txt", "hi");
fileSystem.File.ReadAllText("a.txt");
IFileSystemStatistics stats = fileSystem.Statistics;
await Expect.That(stats.TotalCount).IsEqualTo(2);
await Expect.That(stats.File.Methods).Contains(m => m.Name == nameof(IFile.WriteAllText));
What is recorded
IFileSystemStatistics exposes one property per IFileSystem sub-property:
| Property | Type |
|---|---|
Directory | IStatistics<IDirectory> |
DirectoryInfo | IPathStatistics<IDirectoryInfoFactory, IDirectoryInfo> |
DriveInfo | IPathStatistics<IDriveInfoFactory, IDriveInfo> |
File | IStatistics<IFile> |
FileInfo | IPathStatistics<IFileInfoFactory, IFileInfo> |
FileStream | IPathStatistics<IFileStreamFactory, FileSystemStream> |
FileSystemWatcher | IPathStatistics<IFileSystemWatcherFactory, IFileSystemWatcher> |
FileVersionInfo | IPathStatistics<IFileVersionInfoFactory, IFileVersionInfo> |
Path | IStatistics<IPath> |
IStatistics<T> exposes Methods and Properties collections. Each entry carries the call's name, parameters and a stack-frame counter so you can correlate concurrent activity. IPathStatistics<TFactory, TItem> adds an indexer keyed by the path that the factory produced - stats.FileInfo["a.txt"] returns just the calls made on that specific IFileInfo.
TotalCount returns the sum across every sub-property - handy for "did anything touch the file system at all?" assertions.
What is not recorded
Calls inside the testing helpers themselves (Initialize, InitializeFromRealDirectory, SetCurrentDirectoryToEmptyTemporaryDirectory, …) are excluded from the statistics so seeding does not pollute your assertions. The same goes for any code that explicitly opts out via IgnoreStatistics().