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andydataguy
AI & SYSTEMS

Python tests and logs helped small teams trace failures

Typed data models and shared interfaces supported more than a dozen applications and pipelines.

One shared data model defines every record, and generated tests show bad data stopping at the rule it breaks.

Apps and AI agents pass records through one shared data model whose face has a socket for each shape. Generated tests fire odd records at it: a triangle that fits no socket bounces off, and a square with a bad core fits its socket but is caught by an orange rule test.
12+
applications and pipelines
Type-safe
data contracts
Observable
by default
Property-based
tests
Case Studies

Context

A dozen-plus Python applications and data pipelines built for scrappy teams across industries, internal tools, automations, and agent backends that needed to behave like "real" systems, not side-project scripts.

Problem

The teams I built for ran ad-hoc scripts, fragile unit tests and no observability, and now AI-generated code no one fully understood. Failures were silent.

Approach

I standardized a stack and workflow. Specs first: PRD-style requirement docs broken into task briefs. Data models next: Pydantic types as the single source of truth. APIs via FastAPI so humans and agents share the same interface. Logfire instrumentation for structured observability. Hypothesis property-based tests to explore weird inputs and edge-cases instead of brittle, hand-picked unit tests. Everything wired into CI/CD and, where useful, exposed through MCP.

Stack

  • Python
  • Pydantic
  • FastAPI
  • Hypothesis
  • Logfire
  • MCP/FastMCP
  • CI/CD pipelines

Result

12+
applications and pipelines reported shipped

More than a dozen applications and pipelines shipped on this stack: when something broke, logs and tests pointed to the cause instead of guesswork. Junior developers and agentic coding tools could contribute safely because invariants and data contracts were explicit.

Impact

A small team gets the logs, tests and data contracts a platform team would, without the headcount. I've built on this stack by default ever since.

Lessons

Observability, property-based testing, and type-safe data models are leverage for small teams rather than enterprise-only extras.

Who this is for

For founders and technical leads who want Python-based automations and agent infrastructure they can trust long after the first demo.

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