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Testing & modern typing

pytest basics, mocks, type hints, TypedDict, Protocol, and static-checking patterns.

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Testing & modern typing easy

Dependency Injection in Python for Testability

Inject a config dependency into a service so you can swap a real environment-based config for a fake one in tests.

dependency-injection testing mocking
Python 
import os


class Config:
    """Simple config loader that can be easily faked in tests."""
    def get(self, key, default=None):
        return os.environ.get(key, default)


class UserService:
    def __init__(self, config):
        self.config = config

    def get_timeout(self):
        return int(self.config.get(…
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