Why does it prefer build() over insert() in factories?

Using build/2 in factories is significantly faster and avoids unnecessary database writes when a persisted record isn't strictly required for the test logic.

Can it help with testing Phoenix LiveView?

Yes, it includes patterns for render_async, form submissions, and specialized helpers for testing async assigns and event handling in LiveView.

Does it support mocking external services?

Yes, it follows the 'Mock Only at Boundaries' principle, using Elixir behaviors and Mox to create reliable contracts for external APIs and file storage.

How does this skill handle database isolation?

It strictly enforces Ecto.Adapters.SQL.Sandbox for all database tests to ensure concurrent execution doesn't leak state between test cases.

Elixir & Phoenix Testing

Name: Elixir & Phoenix Testing
Author: oliver-kriska

byoliver-kriska

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Security & Testing

Implements robust Elixir testing patterns using ExUnit, Mox, and Phoenix LiveView test helpers for high-performance suites.

This skill equips Claude with specialized knowledge to write high-quality, asynchronous Elixir tests for Phoenix applications. It enforces industry-best 'Iron Laws' such as sandbox isolation, behavior-based mocking with Mox, and factory optimization with ExMachina to ensure test suites remain fast, reliable, and isolated. Whether you are debugging flaky tests, setting up LiveView assertions, or defining complex database factories, this skill provides the domain-specific guidance needed to maintain a production-grade testing environment without violating Elixir's concurrency model.

Key Features

01Optimizes database interactions using ExMachina build/2 and insert/2 patterns.

02Standardizes behavior-based mocking using Mox with mandatory contract verification.

0362 GitHub stars

04Identifies and fixes common anti-patterns like Process.sleep and global state leaks.

05Provides specialized assertions for Phoenix LiveView, ConnCase, and DataCase.

06Enforces 'Async by Default' and Ecto Sandbox isolation for high-performance test suites.

Use Cases

01Refactoring legacy or flaky test suites to resolve sandbox errors and race conditions.

02Setting up mock behaviors and contracts for external API integrations and service boundaries.

03Developing unit and integration tests for Phoenix controllers, contexts, and LiveViews.

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add oliver-kriska/claude-elixir-phoenix testing

For use in Claude.ai and ChatGPT

Download Skill