Add D-MemFS: in-process virtual filesystem for testing

[nightmarewalker]

Description

Hello! I'd like to propose adding D-MemFS to the Mocks section (alongside pyfakefs).

While pyfakefs is excellent for patching global os/open() state, D-MemFS serves a different architectural need: it provides an explicit, isolated filesystem instance that you pass around via dependency injection. This means no monkey-patching and zero side effects on other code.

• Full FS Semantics: Hierarchical directories, hard quota enforcement, and file-level RW locking.
• Concurrency Ready: Fully thread-safe, including support for free-threaded Python 3.13 (PYTHON_GIL=0).
• Zero Dependencies: Relies purely on the Python standard library.
• Proven Stability: 369 tests, 97% coverage, tested across 3 OS × 3 Python versions in CI.
• Community Validated: Discussed on r/Python with positive reception.

I believe it provides a valuable, explicit alternative for testing I/O-heavy code. Thank you for maintaining this awesome list!

Summary by Sourcery

Documentation:

• Document D-MemFS as an in-memory virtual filesystem mock in the README mocks section.

[semanticdiff-com]

Review changes with  

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adds D-MemFS to the README’s Mocks section as an additional in-memory filesystem testing utility, including a short descriptive tagline clarifying its explicit-instance, zero-dependency design and hard quota support.

File-Level Changes

Change	Details	Files
Document D-MemFS as an additional mocking library in the README under the Mocks section.	Insert a new bullet in the Mocks list for D-MemFS with a GitHub link. Describe D-MemFS as a zero-dependency in-memory virtual filesystem with hard quotas. Clarify that D-MemFS provides an explicit, isolated filesystem instance instead of patching global state.	README.md

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[qodo-code-review]

Review Summary by Qodo

Add D-MemFS to Mock and Stub testing resources

✨ Enhancement

Walkthroughs

Description

• Add D-MemFS to Mock and Stub section
• Provides in-memory virtual filesystem alternative to pyfakefs
• Emphasizes explicit dependency injection over monkey-patching

Diagram

flowchart LR
  README["README.md<br/>Mock and Stub Section"]
  DMEMFS["D-MemFS Entry<br/>In-memory Virtual FS"]
  README -- "adds entry" --> DMEMFS

Loading

File Changes

1. README.md 📝 Documentation +1/-0

Add D-MemFS mock filesystem resource entry

• Added D-MemFS entry to the Mock and Stub section
• Positioned alphabetically between Cornell and doublex entries
• Includes description highlighting zero-dependency design and explicit instance approach

README.md

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[qodo-code-review]

Code Review by Qodo

🐞 Bugs (0) 📘 Rule violations (0) 📎 Requirement gaps (0) 📐 Spec deviations (0)

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Qodo reviewed your code and found no material issues that require review

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[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces D-MemFS, a zero-dependency, in-memory virtual filesystem, to the list of testing resources. D-MemFS distinguishes itself by offering an explicit, isolated filesystem instance, contrasting with traditional global state patching methods. The inclusion of D-MemFS aims to provide developers with a concurrency-ready and community-validated tool for I/O-heavy code testing.

Highlights

• Introduction of D-MemFS: This PR proposes adding D-MemFS to the list of mocking resources, offering an in-memory virtual filesystem for testing.
• Key Features of D-MemFS: D-MemFS provides full filesystem semantics, concurrency support, and zero dependencies, making it a robust alternative to patching global state.
• Community Validation: The addition of D-MemFS is backed by community discussion and positive reception, indicating its potential value to developers.

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[llamapreview]

Auto Pull Request Review from LlamaPReview

Review Status: Automated Review Skipped

Dear contributor,

Thank you for your Pull Request. LlamaPReview has analyzed your changes and determined that this PR does not require an automated code review.

Analysis Result:

PR only contains documentation changes (1 files)

Technical Context:

Documentation changes typically include:

• Markdown/RST file updates
• API documentation
• Code comments
• README updates
• Documentation in /docs directory
• License and contribution files

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[sourcery-ai]

Hey - I've reviewed your changes and they look great!

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[gemini-code-assist]

Code Review

This pull request adds D-MemFS, an in-memory virtual filesystem, to the 'Mock and Stub' section of the README. The new entry is placed correctly in alphabetical order and the description highlights its key features. The change is a straightforward addition to the list. The PR description also positions D-MemFS as an alternative to pyfakefs. Given that pyfakefs is a widely-used library for filesystem mocking but is not currently included in the list, you might consider adding it as well to enhance the comprehensiveness of this resource.

[nightmarewalker]

I've also added pyfakefs to the list, as the automated code review pointed out that it was missing. Since I mentioned it as a comparison in my description, it makes sense to have it in the same section for completeness!