---
layout: page
published: true
noToc: false
noComments: false
noDate: false
title: Writing Tests
subtitle: How to author new tests for Fun and opcode components.
description: How to author new tests for Fun and opcode components.
permalink: /documentation/writing-tests/
lang: en
tags:
- author
- components
- new
- opcode
- tests
- writing
---

How to author tests for Fun and its opcode implementations.

## Test kinds

- VM/opcode tests: exercise bytecode operations and VM behavior (target: `test_opcodes`).
- Language/runtime tests: exercise user-visible features and stdlib behavior (target: `fun_test`).

See `documentation/testing.md` for how to build and run these targets with CTest.

## Adding new tests

The exact layout may evolve; generally:
- Add new test sources alongside existing ones used by `fun_test`.
- For opcode-focused tests, add cases where `test_opcodes` discovers them.

Aim for:

- Small, isolated test cases with clear assertions
- One behavior per test; descriptive names
- Minimal fixtures and setup

## Guidelines

- Prefer black-box testing via public APIs.
- When adding features, include both positive and negative cases.
- Keep tests deterministic; avoid non-deterministic timers or random sources unless seeded.