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.
npx skills add aj-geddes/useful-ai-prompts --skill mocking-stubbinggit clone --depth 1 https://github.com/aj-geddes/useful-ai-promptsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/aj-geddes/useful-ai-prompts/mocking-stubbing)<a href="https://agentmods.dev/skills/aj-geddes/useful-ai-prompts/mocking-stubbing"><img src="https://agentmods.dev/badge/skills/aj-geddes/useful-ai-prompts/mocking-stubbing/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/aj-geddes/useful-ai-prompts/mocking-stubbing"><img src="https://agentmods.dev/badge/skills/aj-geddes/useful-ai-prompts/mocking-stubbing.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00047 | $0.00696 |
| Opus 5 | $0.00023 | $0.00348 |
| Sonnet 5 | $0.00009 | $0.00139 |
| Haiku 4.5 | $0.00005 | $0.00070 |
Grade A, and why
mocking-stubbing 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 9d 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.
How it starts
The opening of the file, as written. The whole thing — 100 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Mocking and Stubbing
Table of Contents
Overview
Mocking and stubbing are essential techniques for isolating units of code during testing by replacing dependencies with controlled test doubles. This enables fast, reliable, and focused unit tests that don't depend on external systems like databases, APIs, or file systems.
When to Use
- Isolating unit tests from external dependencies
- Testing code that depends on slow operations (DB, network)
- Simulating error conditions and edge cases
- Verifying interactions between objects
- Testing code with non-deterministic behavior (time, randomness)
- Avoiding expensive operations in tests
- Testing error handling without triggering real failures
Quick Start
Minimal working example:
// services/UserService.ts
import { UserRepository } from "./UserRepository";
import { EmailService } from "./EmailService";
export class UserService {
constructor(
private userRepository: UserRepository,
private emailService: EmailService,
) {}
async createUser(userData: CreateUserDto) {
const user = await this.userRepository.create(userData);
await this.emailService.sendWelcomeEmail(user.email, user.name);
return user;
}
async getUserStats(userId: string) {
const user = await this.userRepository.findById(userId);
if (!user) throw new Error("User not found");
const orderCount = await this.userRepository.getOrderCount(userId);
return { ...user, orderCount };
}
}
// ... (see reference guides for full implementation)
Reference Guides
Detailed implementations in the references/ directory:
| Guide | Contents |
|---|---|
| Jest Mocking (JavaScript/TypeScript) | Jest Mocking (JavaScript/TypeScript) |
| Python Mocking with unittest.mock | Python Mocking with unittest.mock |
| Mockito for Java | Mockito for Java |
| Advanced Mocking Patterns | Advanced Mocking Patterns |
What ships with it
6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 9d ago First seen · 100 lines · 47 tokens per session scan A dcff21893ca5
mocking-stubbing is a skill published in the GitHub repository aj-geddes/useful-ai-prompts (338 stars, last pushed 6mo ago), licensed MIT. It adds 47 tokens to every session and 696 once invoked, about $0.0002 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 2026-09-03.
Other skills, from other repositories
migrate-xunit-to-xunit-v3
Migrate .NET test projects from xUnit.net v2 to xunit.v3 and fix v3 breaks. Use for package/CPM conversion, OutputType=Exe, preserving the VSTest or MTP runner (including projects currently using YTest.MTP.XUnit2), incompatible TFMs, async void tests, string-to-Type attributes, custom Fact/Theory/BeforeAfterTest…
go-testing
Trigger: Go tests, go test coverage, Bubbletea teatest, golden files. Apply focused Go testing patterns.
nw-fp-clojure
Clojure language-specific patterns, data-first modeling, REPL-driven development, and spec.
mobiai-ios-testing
Use when writing or running tests in an iOS project — unit tests, UI tests, snapshot tests, choosing the right framework.
junit-5-skill
Generates production-grade JUnit 5 unit and integration tests in Java. Covers assertions, parameterized tests, lifecycle hooks, mocking with Mockito, and nested tests. Use when user mentions "JUnit", "JUnit 5", "@Test", "assertEquals", "Assertions", "Java unit test". Triggers on: "JUnit", "@Test", "assertEquals"…
restore-internals-seams-in-finally-blocks-after-each-test
When delegating a task affected by this skill, include.