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Testing Vector Environment Wrapper Implementation in OpenAI Gym

This test suite validates the VectorEnvWrapper functionality in OpenAI Gym’s vectorized environment implementation. It focuses on testing wrapper inheritance and attribute management for vectorized environments, ensuring proper environment state handling and attribute propagation.

Test Coverage Overview

The test suite covers core functionality of the VectorEnvWrapper class with specific focus on inheritance patterns and attribute management.

Tests wrapper inheritance through reset functionality verification
Validates attribute forwarding between wrapped and base environments
Covers multiple environment instances with num_envs parameter
Tests synchronous and asynchronous environment configurations

Implementation Analysis

The testing approach implements a DummyWrapper class to verify the base VectorEnvWrapper functionality. It utilizes both synchronous and asynchronous environment configurations, demonstrating wrapper behavior with different environment types (FrozenLake and CartPole).

The implementation showcases NumPy array comparisons for attribute verification and proper environment state management through reset operations.

Technical Details

Testing Framework: Python’s built-in unittest/pytest
Dependencies: NumPy for array comparisons
Environment Types: FrozenLake-v1, CartPole-v1
Vector Environment Configuration: Supports both synchronous and asynchronous modes
Wrapper Implementation: Custom DummyWrapper class extending VectorEnvWrapper

Best Practices Demonstrated

The test suite demonstrates several testing best practices for environment wrappers.

Clear separation of concerns between inheritance and attribute testing
Proper environment cleanup and state management
Explicit attribute verification using numpy comparisons
Comprehensive testing of both single and multi-environment scenarios

openai/gym

tests/vector/test_vector_env_wrapper.py

            
import numpy as np

from gym.vector import VectorEnvWrapper, make


class DummyWrapper(VectorEnvWrapper):
    def __init__(self, env):
        self.env = env
        self.counter = 0

    def reset_async(self, **kwargs):
        super().reset_async()
        self.counter += 1


def test_vector_env_wrapper_inheritance():
    env = make("FrozenLake-v1", asynchronous=False)
    wrapped = DummyWrapper(env)
    wrapped.reset()
    assert wrapped.counter == 1


def test_vector_env_wrapper_attributes():
    """Test if `set_attr`, `call` methods for VecEnvWrapper get correctly forwarded to the vector env it is wrapping."""
    env = make("CartPole-v1", num_envs=3)
    wrapped = DummyWrapper(make("CartPole-v1", num_envs=3))

    assert np.allclose(wrapped.call("gravity"), env.call("gravity"))
    env.set_attr("gravity", [20.0, 20.0, 20.0])
    wrapped.set_attr("gravity", [20.0, 20.0, 20.0])
    assert np.allclose(wrapped.get_attr("gravity"), env.get_attr("gravity"))