Bugnik

Beta · Free to start

Practise fixing broken repos before your coding assessment.

Real multi-file projects with seeded bugs. Fix them in the browser, run the tests, then submit against hidden ones.

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The editor with an example multi-file C++ project: one line is fixed and all tests pass.

Why this exists

Algorithm practice doesn't train you for a repo.

Online assessments now include a question where you get a whole project, a list of failing behaviour and limited time. It's a different skill from writing one function from scratch.

  • A codebase you've never seen

    The repo question hands you several files you didn't write. Every problem here is a real multi-file project: headers, services, tests and a build script.

  • Tests you can't see

    Passing the visible tests isn't enough. Submit runs hidden tests that check the edge cases, so you learn to look for them before they cost you.

  • The clock

    Each problem has a suggested time and a stopwatch you control, so you can practise at exam pace or slow down to learn.

What you can do

Everything the exam has, and the feedback it doesn't give you.

  • Code in the browser

    VS Code's editor with a file tree. Your code is saved as you type.

  • Run the visible tests

    As often as you like, with expected vs actual and a jump to the failing line.

  • Submit to hidden tests

    Graded in an isolated container. See your visible and hidden scores.

  • Review your fix

    Every submission keeps a diff of exactly what you changed.

  • Hints and editorials

    Hints that point to the bug, then the reference fix explained.

  • Track your progress

    Solved, in progress, and which problems changed since you started.

How it works

Three steps, no setup.

  1. 1

    Pick a problem

    A small multi-file project with seeded bugs, or a feature left for you to implement.

  2. 2

    Fix it in the browser

    Read the code, edit it in the built-in editor and run the visible tests until they pass.

  3. 3

    Submit against hidden tests

    Hidden tests check the cases you didn't see, like the real assessment. Then review your diff and move on to the next one.

Start here

Start with one of these.

See all 30 problems

Why not just LeetCode?

Different questions train different skills.

  • Starting point

    Algorithm sites
    An empty function

    Bugnik
    An existing project of several files

  • Main skill

    Algorithm sites
    Designing an algorithm

    Bugnik
    Reading code, finding and fixing bugs, adding a feature

  • Tests

    Algorithm sites
    Input/output cases

    Bugnik
    Unit tests in the project's own framework, plus hidden tests

  • Feedback

    Algorithm sites
    Pass or fail per case

    Bugnik
    Build errors and test output, like a real project

Both are worth practising: most assessments have algorithm questions too.

FAQ

Questions people ask first.

What is Bugnik?

A place to practise the code repository question that now appears in online assessments. Each problem is a small multi-file project with seeded bugs or a missing feature. You fix it in the browser and it's graded on visible and hidden tests.

Is this the real assessment?

No. Bugnik is an independent practice platform, not affiliated with any employer or assessment provider. Every problem is original and written in the format of repository-based assessments.

How is my code graded?

Run Tests runs the visible tests that come with the project, as often as you like. Submit runs those plus hidden tests that check cases you can't see. Your code is built and tested on our servers in an isolated container without network access.

Do I need to install anything?

No. You write code in the editor in your browser; the build and the tests run on our servers. You don't need a compiler, a JDK or Docker on your machine.

Is it free?

Yes. Every problem, hint and editorial is free while the site is in beta; you only need an account to start solving. If paid features come later, they will be announced in advance.

Fix your first repo today.

Pick a free problem, make the tests pass, and see how you do on the hidden ones.

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