python

pytest-substrate

pytest plugin for the substrate AWS emulator.

Installation

pip install pytest-substrate
# or, from source:
pip install -e /path/to/substrate/python

Usage

Add the substrate fixture to any test that needs AWS services:

import boto3

def test_s3_upload(substrate):
    s3 = boto3.client("s3")
    s3.create_bucket(Bucket="my-bucket")
    s3.put_object(Bucket="my-bucket", Key="hello.txt", Body=b"hello")
    obj = s3.get_object(Bucket="my-bucket", Key="hello.txt")
    assert obj["Body"].read() == b"hello"

The substrate fixture:

• Starts a substrate server once per test session (via substrate_server)
• Resets all state before each test
• Sets AWS_ENDPOINT_URL, AWS_DEFAULT_REGION, and dummy credentials via monkeypatch

Fixtures

substrate_server (session-scoped)

Manages the substrate process lifecycle. Starts once, stops after all tests complete.

substrate (function-scoped)

Resets state and configures env vars. Yields the SubstrateServer instance.

Configuration

Set SUBSTRATE_BINARY to override the binary path. Otherwise, the plugin looks for:

1. ~/src/substrate/bin/substrate
2. substrate on PATH