Table of Contents

Ploch.TestingSupport.FluentAssertions.IOAbstractions

FluentAssertions extensions for asserting on collections of System.IO.Abstractions file system objects.

Overview

Ploch.TestingSupport.FluentAssertions.IOAbstractions adds FluentAssertions-style assertion methods for working with the TestableIO.System.IO.Abstractions abstraction layer. When tests verify directory listings, file sets, or other file-system collections returned through IFileSystem, this library lets you write readable, failure-reporting assertions rather than manual LINQ comparisons.

The central type is FileSystemInfoAssertions<TItems>, which extends GenericCollectionAssertions<TItems> and adds name-based equivalence checks that handle path-separator normalisation automatically. The three Should() extension methods on IEnumerable<IFileSystemInfo>, IEnumerable<IDirectoryInfo>, and IEnumerable<IFileInfo> are the entry points.

The library targets netstandard2.0 and has two dependencies: FluentAssertions and TestableIO.System.IO.Abstractions.

Installation

dotnet add package Ploch.TestingSupport.FluentAssertions.IOAbstractions

Key Types

Type Namespace Description
FileSystemInfoAssertions<TItems> TestingSupport.FluentAssertions.IOAbstractions Extends GenericCollectionAssertions<TItems> for IFileSystemInfo collections. Provides HaveNamesEquivalentTo, HaveNamesEquivalentToIgnoringCase.
FileSystemInfoEnumerableExtensions TestingSupport.FluentAssertions.IOAbstractions Adds Should() to IEnumerable<IFileSystemInfo>, IEnumerable<IDirectoryInfo>, and IEnumerable<IFileInfo>.

Usage Examples

Asserting directory contents by name (case-insensitive)

IFileSystem fileSystem = new FileSystem(); // or a mock
var directory = fileSystem.DirectoryInfo.New("/my/project");

directory.GetDirectories()
         .Should()
         .HaveNamesEquivalentToIgnoringCase("src", "tests", "docs");

Trailing path separators are stripped automatically before comparison, so "src/" and "src" are treated as equal.

Asserting with a custom equality comparer

directory.GetFiles()
         .Should()
         .HaveNamesEquivalentTo(
             new[] { "Program.cs", "Startup.cs" },
             StringComparer.Ordinal,
             because: "the file names must match exactly");

Mixed IFileSystemInfo collection

IEnumerable<IFileSystemInfo> entries = directory.GetFileSystemInfos();

entries.Should()
       .HaveNamesEquivalentToIgnoringCase("README.md", "src", "tests");

Using with a mocked file system

The assertions integrate directly with MockFileSystem from System.IO.Abstractions.TestingHelpers, enabling fully in-memory file system tests:

var mockFs = new MockFileSystem(new Dictionary<string, MockFileData>
{
    { "/project/src/Program.cs", new MockFileData("// code") },
    { "/project/tests/MyTests.cs", new MockFileData("// tests") }
});

mockFs.DirectoryInfo.New("/project")
      .GetDirectories()
      .Should()
      .HaveNamesEquivalentToIgnoringCase("src", "tests");
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