Coding test platform to replace in-house tests_

Codility Screen gives each candidate a realistic engineering task and scores the output of selected task types against test cases. Your engineers no longer write the test by hand or mark the automatically scored tasks.

Request a free trial

verifiedOver 1,300 tasks, each designed by assessment engineers, reviewed by occupational psychologists and tested for AI solvability.

Backend engineer assessment

check_circleTask 1 Task 2 Task 3

schedule41:18 left Submit task

Task 2 of 3

Inventory reservation service

Java Spring Medium

An online store reserves stock when a customer starts checkout. Implement ReservationService so that concurrent reservations never oversell an item.

Requirements

reserve(sku, quantity) decrements available stock
Throw InsufficientStockException when stock is too low
release(id) returns stock to the inventory
Reservations expire after 15 minutes

$ mvn test

description search account_tree bug_report extension

Explorer

expand_moreinventory-service

folder_opensrc/main/java

codeInventory.java

codeReservationService.java

codeReservationController.java

folder_opensrc/test/java

scienceReservationServiceTest.java

data_objectpom.xml

articleREADME.md

ReservationService.java Inventory.java

1

package com.shop.inventory;

2

3

@Service

4

public class ReservationService {

5

6

    private final InventoryRepository inventory;

7

    private final ReservationRepository reservations;

8

9

    @Transactional

10

    public Reservation reserve(String sku, int quantity) {

11

        Inventory item = inventory.findBySkuForUpdate(sku)

12

            .orElseThrow(() -> new SkuNotFoundException(sku));

13

14

        if (item.available() < quantity) {

15

            throw new InsufficientStockException(sku, quantity);

16

}

17

18

        // TODO: expire reservations after 15 minutes

19

        item.decrement(quantity);

20

        return reservations.save(new Reservation(sku, quantity));

21

}

22

}

TerminalProblemsOutput

$ mvn test -q
[INFO] Running ReservationServiceTest
[ERROR] concurrentReserve_doesNotOversell
        expected: <0> but was: <-1>
[ERROR] expiredReservation_isReleased
[INFO] Tests run: 9, Failures: 2, Errors: 0
$ 

Test results play_arrowRun tests

7 of 9 passed0.84 s

check_circle reserve_decrementsStock 14 ms

check_circle reserve_unknownSku_throws 6 ms

check_circle reserve_insufficientStock_throws 5 ms

check_circle release_restoresStock 11 ms

check_circle release_twice_isIdempotent 9 ms

cancel concurrentReserve_doesNotOversell 212 ms

cancel expiredReservation_isReleased 31 ms

check_circle controller_returns201 48 ms

check_circle controller_returns409OnConflict 22 ms

Recognized by G2 in Fall 2026

Codility is rated 4.6 out of 5 on G2 and ranked #1 for Enterprise Technical Skills Screening. Rankings come from verified customer reviews.

Today’s failing approach: in-house coding tests that your engineers build and mark

schedule

Failing approach 1

Engineer time

Your engineers write the test, keep it up to date and mark each submission by hand. Every new candidate adds marking time to an engineer’s week.

public

Failing approach 2

Leaked questions

If your in-house test reuses the same questions, a posted solution can give later candidates the answer before they start.

smart_toy

Failing approach 3

AI-generated answers

A candidate can paste a take-home task into an AI chat tool and submit the generated answer. The final answer alone does not show how the candidate produced the code.

extension_off

Failing approach 4

Tasks unlike the role

Your engineers can write an algorithm exercise faster than a realistic task. HackerRank’s 2025 Developer Skills Report found that 78% of developers say assessments don’t align with real-world tasks.

Replace your in-house coding test with validated work simulations

Codility Screen is a coding test platform for the screening stage of engineering hiring. Candidates complete realistic engineering tasks. You can include tasks built for a full VS Code environment. Your talent team then builds the shortlist for each role from the scored results.

Choose ready-made tasks instead of writing your own

You choose the tasks for each role from Codility’s library. The library covers technologies including React, Spring, Kubernetes and Terraform. Codility removes leaked tasks from the library.

Build with MCP also lets your engineers create tasks for parts of your stack that the library does not cover. An engineer describes the task to an AI coding assistant such as Claude, Cursor or GitHub Copilot.

The assistant then builds the task, its test cases and a reference solution. The engineer reviews the task before publishing it. Most tasks take about ten minutes from description to publication.

The difference: Codility maintains the task library, so your engineers no longer keep the test up to date.

arrow_backBack Edit assessment

check_circleSelect tasks chevron_right 2Order tasks chevron_right 3Settings chevron_right 4Save

shopping_cart4 tasks · 105 min Continue

Backend engineer (Java)

4 tasks · 105 min total. Order tasks from easiest to hardest.

addAdd tasks

TaskTechnologyDifficultyTime

drag_indicator bug_report

Fix the payment retry bug

Find and fix a bug that charges a customer twice on retry.

Java

Easy 20 min close

drag_indicator database

Order history query

Write a query that returns a customer’s order history with totals.

SQL

Medium 25 min close

drag_indicator code

Inventory reservation service

Prevent overselling when customers check out at the same time.

Java + Spring

Medium 35 min close

drag_indicator code

Ledger reconciliation jobCompany task

Match payment provider records against the internal ledger.

Java

Hard 25 min close

Task library

searchSearch tasks

All Codility Company

Technologyexpand_more Job roleexpand_more Difficultyexpand_more

Deploy a service to Kubernetes

Medium40 min

Add

Terraform module for object storage

Easy30 min

Add

Checkout form validation

Medium45 min

Add

Screenchevron_rightBackend engineer (Java)

Backend engineer (Java) Active

tuneCut score: 70% Invite candidates

Candidates Analytics Tasks Settings

Assessments completed

48

Reached the cut score

17of 48 · 35%

Score distribution

At or above cut score Below cut score

1

2

3

4

6

8

7

8

6

3

Cut score 70%

0102030405060708090

CandidateCompletedScoreTest cases passedCut scoreATS

DO

Daniel Okafor

[email protected]

Sep 30

76%

68 of 90 check_circleAbove cut score syncGreenhouse

MT

Mei Tanaka

[email protected]

Sep 30

48%

41 of 90 remove_circleBelow cut score syncGreenhouse

LM

Lucas Moreau

[email protected]

Sep 29

91%

84 of 90 check_circleAbove cut score syncGreenhouse

SL

Sara Lindqvist

[email protected]

Sep 29

63%

55 of 90 remove_circleBelow cut score syncGreenhouse

AM

Arjun Mehta

[email protected]

Sep 28

84%

77 of 90 check_circleAbove cut score syncGreenhouse

EP

Elena Petrova

[email protected]

Sep 28

72%

64 of 90 check_circleAbove cut score syncGreenhouse

Score submissions automatically against test cases

Codility automatically scores the output of selected task types, including coding, bug-fixing, SQL and front-end tasks. Codility’s scoring is deterministic, so the same output always earns the same score.

You set the cut score, the minimum overall score that your team expects for the role. Your talent team then sees how many candidates reached the cut score. Codility connects with applicant tracking systems (ATS), including Greenhouse, Lever, Workday and SmartRecruiters. Codility stores each result in the candidate’s ATS record. Automatically scored tasks need no manual marking by your engineers.

The difference: Automatically scored tasks use the same scoring rules for every candidate.

Review how each candidate built the solution

Codility stores the submitted code and the test-case breakdown with each result, for the period set in your retention policy. Your engineers can open the Code Evolution Chart, a timeline of how the code changed during the assessment.

Codility can also collect integrity signals, which give reviewers evidence about how the candidate produced the submission. The signals include paste events, similarity checks against other candidates and identity verification.

You decide whether candidates can use the AI Assistant in each assessment. Where the AI Assistant is enabled, every candidate interaction is captured as reviewable AI activity.

The difference: Your reviewers see how the candidate reached the answer, in addition to the answer itself.

Request a free trial

PR

Priya RamanBackend engineer (Java)

Completed Sep 30, 2026 · Time spent 1 h 32 min

pendingAwaiting reviewer decision

linkCopy link picture_as_pdfExport PDF

Summary Candidate solution Integrity AI activity

77%Total score

Correctness

23 of 30 tests passed

Example tests2 / 2

Functional tests15 / 18

Performance tests6 / 10

Code Evolution Chart

Code size Paste event AI interaction

Integrity signalResult

content_paste

Paste events

2 pastes into ReservationService.java

2 found Show in timeline

difference

Similarity check

Compared with other candidates for this task

Not found

badge

Identity verification

ID document matched the candidate

Verified

AI activityAI Assistant enabled

3 interactions captured during the assessment

auto_awesomePrompt00:38

How do I lock a row for update in Spring Data JPA?

auto_awesomeResponse00:38

Suggested a pessimistic write lock on the repository query method.

auto_awesomePrompt01:14

Why would a reservation expiry test fail with a fixed clock?

View full transcript

Questions about coding test platforms

What is a coding test platform?

A coding test platform gives candidates programming tasks and records their solutions. Codility Screen scores selected task types against test cases. An online coding test platform also stores the results for your hiring team. Talent teams use a coding test platform in place of tests that engineers write and mark by hand.

What should replace take-home coding tests that candidates solve with AI?

Should we build our own coding tests or buy a platform?

Does Codility make automated hiring decisions?

Do candidates find the assessment fair?

Replace your in-house test on one engineering role_

Bring one engineering role that your team currently tests in-house. Codility will show you the tasks for that role and how your team would review the scored results.

"*" indicates required fields

Comments

This field is for validation purposes and should be left unchanged.

Business email*

First name*

Last name*

Job title*

Company*

Direct phone number

What can we help with? (select all that apply)*

Assess candidates (Screen)

Improve technical interviews (Interview)

Understand my team’s skills (Skills Intelligence)

Replace or evaluate your current platform

I’m an existing customer

Something else

Please tell us more*

Roughly how many hires do you expect this year?*

How many employees does your company have?*

Anything you'd like us to know? (optional)

How did you find us? (optional)

Please tell us how you found us*

utm_source

utm_medium

utm_campaign

utm_content

utm_term

landing_page

referring_page

First touch date

First touch source

First touch medium

First touch campaign

First touch content

First touch term

First touch click ID

First touch referrer

First touch landing page

Most recent touch date

Most recent touch source

Most recent touch medium

Most recent touch campaign

Most recent touch content

Most recent touch term

Most recent touch click ID

Most recent touch referrer

Most recent touch landing page

GCLID

AB variant