Which languages can I use in a coding interview?

Python, JavaScript, TypeScript, Java, C++, C#, Go, Rust and Kotlin. Every algorithm, object-oriented design and AI-assisted coding question offers all nine.

Yes, in Runnable Coding. Run executes your entry point and any test files that follow your language’s naming convention, such as test_*.py, *.test.ts, *Test.java or *_test.go.

Does the interviewer see my runs?

Yes. Each run’s output and test results reach the interviewer, who may ask about a failure or about cases you have not tested. The report also takes your runs into account.

Is there autocomplete?

Runnable Coding has basic, non-AI completion and import suggestions. Whiteboard Coding (No Run) has none, to match interviews held in a plain editor.

Nine languages · Runnable sandbox

Code in the language you will interview in

Answer algorithm, object-oriented design and AI-assisted coding questions in Python, JavaScript, TypeScript, Java, C++, C#, Go, Rust and Kotlin. Run your code in an isolated sandbox while the interviewer follows your results.

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Key facts

Every coding question (algorithm, object-oriented design and AI-assisted coding) can be answered in any of nine languages: Python, JavaScript, TypeScript, Java, C++, C#, Go, Rust and Kotlin.
You pick the language in the editor once the interview starts and can switch at any time; the interviewer follows along.
Algorithm questions use a single-file editor; object-oriented design and AI-assisted coding questions use a multi-file workspace with a file tree.
Runnable Coding: Run executes your entry point and your test files in an isolated sandbox with no network access, and the interviewer sees each run.
Whiteboard Coding (No Run): line numbers and syntax highlighting only, no autocomplete and no Run; you validate with written tests and a verbal walkthrough.
AI-assisted coding questions always use Runnable Coding.
The coding mode you choose stays fixed for the interview, including when you resume it.

Coding modes

Run your code, or practice without a Run button

Choose the mode that matches the interview you expect. It stays fixed for the interview.

Runnable Coding

Basic non-AI completion and common standard-library import suggestions. Run your main entrypoint and supported test files in the execution service. Not a full IDE outside JavaScript/TypeScript.

Whiteboard Coding (No Run)

Line numbers, syntax highlighting, and basic indentation. No autocomplete, snippets, auto-imports, live diagnostics, or Run. Validate with written tests and verbal walkthroughs.

Workspaces

One editor per kind of question

Algorithm questions

One file per language, with a main entry point you call your solution from. Each language keeps its own draft when you switch.

Object-oriented design

A multi-file workspace: create, rename and delete files, and build the classes and interfaces the design needs.

AI-assisted coding

A multi-file repository, sometimes an existing codebase, with EngMock’s coding assistant in a panel beside the code.

Tests

Test files that Run picks up

Run executes your entry point plus any file that follows your language’s test naming convention.

Language	Test files
Python	test_.py or _test.py
JavaScript	.test.js or .spec.js
TypeScript	.test.ts or .spec.ts
Java	Test.java or Tests.java
C++	.test.cpp or _test.cpp
C#	Test.cs or Tests.cs
Go	*_test.go
Rust	*_test.rs
Kotlin	Test.kt or Tests.kt

Limits

Sandbox and workspace limits

Each run gets up to 3 seconds of CPU time (8 seconds in total) for algorithm questions, and up to 8 seconds (15 seconds in total) for multi-file questions.
The sandbox has no network access: code cannot call external services or download packages.
A file can hold up to 50 KB, and a workspace up to 30 files and 1 MB.
Runnable Coding offers basic, non-AI completion and standard-library import suggestions; it is not a full IDE outside JavaScript and TypeScript.

Coding workspace FAQ

Which languages can I use in a coding interview?: Python, JavaScript, TypeScript, Java, C++, C#, Go, Rust and Kotlin. Every algorithm, object-oriented design and AI-assisted coding question offers all nine.
Can I run tests?: Yes, in Runnable Coding. Run executes your entry point and any test files that follow your language’s naming convention, such as test_*.py, *.test.ts, *Test.java or *_test.go.
Does the interviewer see my runs?: Yes. Each run’s output and test results reach the interviewer, who may ask about a failure or about cases you have not tested. The report also takes your runs into account.
Is there autocomplete?: Runnable Coding has basic, non-AI completion and import suggestions. Whiteboard Coding (No Run) has none, to match interviews held in a plain editor.

Try a coding interview

Pick a problem, choose your language in the editor, and run your code while you explain it.

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