Verify call to File.Delete with System.IO.Abstractions.TestingHelpers - unit-testing

Question

I use the System.IO.Abstractions.TestingHelpers to mock FileSystem. In my class, I inject IFileSystem and use the instance to call _fileSystem.File.Exists and _fileSystem.File.Delete. In my test class, I would like to verify that the "Delete" method was called. It's easy by mocking only the IFile, but since I already mocked the FileSystem, I don't want to have to mock the Directory, Path and File on top of it. Is it possible to call something like _fileRepository.FileMock.Verify(x => x.Delete(It.IsAny<string>()))...?
public class Downloader : IDownloader
{
public Downloader(HttpClient httpClient, IFileSystem fileSystem)
{
HttpClient = httpClient;
FileSystem = fileSystem;
}
public async Task DownloadConfigFileAsync(string updatedConfigBaseFolderPath, string configurationFileUrl, string personalAccessToken)
{
var newFilePath = FileSystem.Path.Combine(updatedConfigBaseFolderPath, "subfolder1", "myNewFile.txt");
if (FileSystem.File.Exists(newFilePath))
{
FileSystem.File.Delete(newFilePath);
}
// rest of implementation ommited for demo purpose
}
}
And my test is like :
[Fact]
public async void Given_MissingPathParts_ShouldThrow()
{
var handlerMock = GetMessageHandlerMock();
var mockFileSystem = new MockFileSystem(new Dictionary<string, MockFileData>
{
{ #"c:\Test\", new MockDirectoryData() },
{ #"c:\Test\subfolder1\myNewFile.txt", new MockFileData(string.Empty) }
});
var httpClient = new HttpClient(handlerMock.Object);
var sut = new Downloader(httpClient, mockFileSystem);
await sut.DownloadConfigFileAsync(BasePath, "http://fakeurl.com?path=%2Fconfiguration%2Flocal%2FTestFile.txt", _fixture.Create<string>());
handlerMock.Protected().Verify(
"SendAsync",
Times.Exactly(1),
ItExpr.Is<HttpRequestMessage>(req => req.Method == HttpMethod.Get),
ItExpr.IsAny<CancellationToken>());
mockFileSystem.File.Exists(FilePath).Should().BeTrue();
// Add assertion that the File.Delete has been called
}

Answer 1

The test freamwork has extensive unit tests itself.
Looking into ...tests\TestableIO.System.IO.Abstractions.TestingHelpers.Tests\MockFileDeleteTests.cs, it just counts the files, which I don't find overly satisying. If there would be a direct way, the creator would have used it.
var fileCount1 = fileSystem.Directory.GetFiles(directory, "*").Length;
fileSystem.File.Delete(path);
var fileCount2 = fileSystem.Directory.GetFiles(directory, "*").Length;
Assert.AreEqual(1, fileCount1, "File should have existed");
Assert.AreEqual(0, fileCount2, "File should have been deleted");