tdd

A test-first workflow for Java, Python, and TypeScript code in OpenMetadata. Test-driven development (TDD) means writing a failing test, making the code pass it, and then improving the code without changing its behaviour.

In plain words
What is it for?
Use it when adding features, fixing bugs, creating API endpoints or connectors, or building interface components. It guides tests using JUnit, pytest, Jest, and Playwright.
Why use it?
It makes the intended behaviour explicit before implementation and helps prevent new features or bug fixes from working only for the case the developer happened to try.

Skill for Claude CodeCodex

Part of the openmetadata-skills plugin — 20 skills, 5 commands, 6 agents, 1 hook shipped together

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/open-metadata/openmetadata/tdd
Any agent
npx skills add open-metadata/OpenMetadata --skill tdd
Clone the repo
git clone --depth 1 https://github.com/open-metadata/OpenMetadata

Made for: Claude Code, Codex.

Or install openmetadata-skills, the plugin that ships this one along with the rest of its 20 skills, 5 commands, 6 agents, 1 hook.

Per session 50 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,171 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00050 $0.01171
Opus 5 $0.00025 $0.00585
Sonnet 5 $0.00010 $0.00234
Haiku 4.5 $0.00005 $0.00117

Measured 3d ago against content hash bd995ea9698e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

tdd scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/tdd/SKILL.md · 137 lines

How it starts

The opening of the file, as written. The whole thing — 137 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Test-Driven Development for OpenMetadata

Enforce RED-GREEN-REFACTOR discipline across all three language stacks.

When to Use

  • Implementing any new feature or behavior
  • Fixing bugs (write a test that reproduces the bug first)
  • Adding new API endpoints, connectors, or UI components

The Cycle

1. RED - Write a Failing Test

Write the smallest test that describes the desired behavior. Run it. It must fail. If it passes, your test isn't testing the new behavior.

Java (JUnit 5):

# Write test in openmetadata-service/src/test/ or openmetadata-integration-tests/
mvn test -pl openmetadata-service -Dtest=YourTestClass#yourTestMethod

Python (pytest):

source env/bin/activate
cd ingestion
# Write test using pytest style — plain assert, no unittest.TestCase
python -m pytest tests/unit/your_test.py::test_your_function -v

TypeScript (Jest):

cd openmetadata-ui/src/main/resources/ui
yarn test path/to/YourComponent.test.ts

Rules for RED:

  • Test one behavior per test
  • Use descriptive test names that explain what should happen
  • Assert on observable outcomes (API responses, database state, rendered output), not internal method calls
  • For Python: use assert x == y, not self.assertEqual(x, y)

2. GREEN - Write the Minimum Code to Pass

Write only the code needed to make the test pass. No more.

  • Don't add error handling for cases you haven't tested
  • Don't generalize — hardcode if that's what the test requires
  • Don't clean up or refactor yet

Run the test again. It must pass.

3. REFACTOR - Clean Up While Green

Now improve the code while keeping tests green:

  • Remove duplication
  • Improve naming
  • Extract methods if needed (but don't over-abstract)
  • Run the full test suite for the module to check for regressions
# Java — format then test
mvn spotless:apply
mvn test -pl openmetadata-service

# Python — format, lint, then test
cd ingestion && make py_format && make py_format_check
python -m pytest tests/unit/your_test.py -v

# TypeScript — lint then test
cd openmetadata-ui/src/main/resources/ui
yarn lint:fix
yarn test path/to/YourComponent.test.ts

Read the full file on GitHub · 137 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 137 lines · 50 tokens per session scan A bd995ea9698e

Subscribe to this mod's changes

tdd is a skill published in the GitHub repository open-metadata/OpenMetadata (15,059 stars, last pushed yesterday), licensed Apache-2.0. It adds 50 tokens to every session and 1,171 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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