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Migration from TestableIO

Testably.Abstractions and TestableIO.System.IO.Abstractions share the same IFileSystem interface, so production code does not need to change when you switch testing libraries.

When to use which​

Use Testably.Abstractions when you need:

  • Advanced testing scenarios (FileSystemWatcher, SafeFileHandle, multiple drives)
  • Additional abstractions (ITimeSystem, IRandomSystem)
  • Cross-platform file system simulation (Linux, macOS, Windows)
  • More extensive and consistent behavioural validation
  • Active development and new features

Use TestableIO.System.IO.Abstractions when you need:

  • Basic file system mocking
  • Direct manipulation of stored file entities (MockFileData, MockDirectoryData)
  • An established codebase already integrated with TestableIO

How to migrate​

The migration only affects your test projects.

1. Swap the package​

<!-- Remove -->
<PackageReference Include="TestableIO.System.IO.Abstractions.TestingHelpers" />
<!-- Add -->
<PackageReference Include="Testably.Abstractions.Testing" />

2. Update the test code​

// Before (TestableIO)
var fileSystem = new MockFileSystem();
fileSystem.AddDirectory("some-directory");
fileSystem.AddFile("some-file.txt", new MockFileData("content"));

// After (Testably) - option A: imperative
var fileSystem = new MockFileSystem();
fileSystem.Directory.CreateDirectory("some-directory");
fileSystem.File.WriteAllText("some-file.txt", "content");

// After (Testably) - option B: fluent initialization
var fileSystem = new MockFileSystem();
fileSystem.Initialize()
    .WithSubdirectory("some-directory")
    .WithFile("some-file.txt").Which(f => f
        .HasStringContent("content"));

Production code keeps using IFileSystem exactly as before - no changes there.