Principle:Farama Foundation Gymnasium Environment Validation

Knowledge Sources	Gymnasium Env Checker Create Custom Env
Domains	Reinforcement_Learning, Testing
Last Updated	2026-02-15 03:00 GMT

Overview

A validation pattern that systematically checks whether an RL environment implementation conforms to the Gymnasium API contract.

Description

Environment Validation ensures that custom environments correctly implement the Gymnasium interface before deployment. The validation process checks:

Space validity: observation_space and action_space are well-formed Space objects
Reset correctness: reset() returns (observation, info) with observation in observation_space
Step correctness: step() returns the 5-tuple with correct types
Seed determinism: reset(seed=X) produces deterministic results
Step determinism: Given the same seed and actions, step produces identical outputs
Render correctness: render() returns appropriate types for each declared render_mode
Close safety: close() can be called multiple times without error

This is an active validation that calls environment methods with various inputs, unlike the passive checker that validates during normal operation.

Usage

Run validation after implementing a custom environment and as part of continuous integration. Validate the unwrapped environment (without make() wrappers) for the most thorough checks.

Theoretical Basis

Validation follows a contract-based testing approach:

# Abstract validation algorithm
def validate(env):
    assert hasattr(env, 'action_space')
    assert hasattr(env, 'observation_space')

    obs, info = env.reset(seed=42)
    assert obs in env.observation_space

    obs2, info2 = env.reset(seed=42)
    assert obs == obs2  # Seed determinism

    action = env.action_space.sample()
    obs, reward, term, trunc, info = env.step(action)
    assert obs in env.observation_space
    assert isinstance(term, bool)
    assert isinstance(trunc, bool)

Related Pages

Implemented By

Implementation:Farama_Foundation_Gymnasium_Check_Env

Uses Heuristic

Page Connections

Double-click a node to navigate. Hold to expand connections.

Principle

Implementation

Heuristic

Environment