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Mocking Stubbing

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aj-geddes·vlatest·testing·MIT

Mocking Stubbing allows you to create simplified test doubles of dependencies for isolated unit testing, speeding up development and improving test reliability.

Repository

Install on your platform

Showing Claude Code. One command installs this skill into any of the agents below.

  1. 1

    Run this in your project

    terminal
    $ npx skills add aj-geddes/useful-ai-prompts --skill mocking-stubbing -a claude-code

  2. Uses the open-source skills CLI and needs Node.js. Add -g to install it for your user instead of this project.

What we know about this skill

Publisher

aj-geddes

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Live repository

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No human has reviewed this code. The checks below are a static scan of the files at one commit — nobody has run this skill or judged whether it works. A skill runs with whatever access you give your agent, so read the source before you install it.

Automated safety checks

scanned

This skill passed all 6 checks. We read its files at one commit and looked for the things that make a skill dangerous to run — not for whether it works.

  • Declares what it does: passed

    SKILL.md parses and declares a name and a description.

    SKILL.md exists, its frontmatter parses, and it declares a name and a description.

  • No undeclared network calls: passed

    Makes no network calls.

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  • Pinned to a commit: passed

    Scanned aj-geddes/useful-ai-prompts at 3f5182cfd7.

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Commit
3f5182cfd7
Manifest
skills/mocking-stubbing/SKILL.md
Scanned
7 files, 680 lines
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About this skill

The mocking-stubbing skill enables AI agents to generate code for creating test doubles, such as mocks and stubs, to isolate components during unit testing. It helps developers verify logic by simulating external dependencies like databases or APIs without executing them.

When to use it

  • Isolate specific functions or classes from their external dependencies to run fast, deterministic unit tests.
  • Simulate complex or slow external services (e.g., payment gateways, third-party APIs) during development.
  • Enforce expected behaviors in dependent objects by defining return values for specific method calls.
  • Prevent side effects like database writes or network requests when testing pure business logic.

Key capabilities

  • Generates mock objects that mimic the interface of real dependencies.
  • Creates stubs to define fixed return values for specific function inputs.
  • Produces code compatible with popular testing frameworks and languages.
  • Structures test scenarios to verify interactions between components.

Example prompts

  • "Write a Python unit test using unittest.mock to mock an external API call in my service class."
  • "Generate a Jest stub for a database query function that returns a specific user object when called with ID 123."
  • "Create a mock implementation of an email sender interface to test my notification logic without sending actual emails."

Tips & gotchas

Ensure you specify the programming language and testing framework (e.g., Jest, Pytest) to get syntactically correct code. Over-reliance on mocks can lead to tests that pass but fail to catch integration issues, so balance unit tests with occasional integration checks.