A guide to RSpec, a Ruby testing framework used to describe expected program behavior with examples and assertions. It covers test structure, setup helpers, test doubles, and matchers.

Use it when writing or fixing RSpec tests, editing Ruby spec files, or using describe blocks, expectations, doubles, and matchers.

It helps developers write readable Ruby tests and diagnose or correct failing specifications.

rspec — Skill for Claude Code by hoblin

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.

Any agent

npx skills add hoblin/claude-ruby-marketplace --skill rspec

Clone the repo

git clone --depth 1 https://github.com/hoblin/claude-ruby-marketplace

Made for: Claude Code.

Or install rspec, the plugin that ships this one along with the rest of its 1 skill.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/hoblin/claude-ruby-marketplace/rspec.svg)](https://agentmods.dev/skills/hoblin/claude-ruby-marketplace/rspec)

Your own site

<a href="https://agentmods.dev/skills/hoblin/claude-ruby-marketplace/rspec"><img src="https://agentmods.dev/badge/skills/hoblin/claude-ruby-marketplace/rspec.svg" alt="Measured on agentmods" height="20"></a>

Per session 125 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,672 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector pass 7 Sept 2026

How audits are shown

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.

Model	Per session	Once invoked
Fable 5.1	$0.00125	$0.02672
Opus 5	$0.00063	$0.01336
Sonnet 5	$0.00025	$0.00534
Haiku 4.5	$0.00013	$0.00267

Measured 8d ago against content hash 1c70348ca326, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

rspec 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 8d ago.

The scan reads SKILL.md. This mod also ships 49 executable files (examples/core/basic_structure.rb, examples/core/configuration.rb, examples/core/hooks.rb, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

plugins/rspec/skills/rspec/SKILL.md · 350 lines

How it starts

The opening of the file, as written. The whole thing — 350 lines — stays where its author put it; the contents beside it link to each section on GitHub.

RSpec Testing

This skill provides comprehensive guidance for writing effective RSpec tests in Ruby and Rails applications. Use for writing new specs, fixing failing tests, understanding matchers, using test doubles, and following RSpec best practices.

Quick Reference

Basic Structure

RSpec.describe Order do
  subject(:order) { described_class.new(items) }
  let(:items) { [item1, item2] }
  let(:item1) { double("item", price: 10) }
  let(:item2) { double("item", price: 20) }

  describe "#total" do
    it "sums item prices" do
      expect(order.total).to eq(30)
    end
  end

  context "with discount" do
    let(:order) { described_class.new(items, discount: 5) }

    it "applies discount" do
      expect(order.total).to eq(25)
    end
  end
end

Key Concepts

Concept	Purpose
`describe` / `context`	Group related examples
`it` / `specify`	Define individual test cases
`let`	Lazy-evaluated, memoized helper
`let!`	Eager-evaluated helper (runs before each example)
`subject`	Primary object under test
`before` / `after`	Setup and teardown hooks
`expect`	Make assertions

Writing Good Specs

Use Named Subject for Method Tests

describe "#calculate_total" do
  subject(:total) { order.calculate_total }

  it "returns sum of items" do
    expect(total).to eq(100)
  end
end

Context Blocks for Different States

describe "#withdraw" do
  context "with sufficient funds" do
    let(:account) { build(:account, balance: 100) }

    it "reduces balance" do
      expect { account.withdraw(50) }.to change(account, :balance).by(-50)
    end
  end

  context "with insufficient funds" do
    let(:account) { build(:account, balance: 10) }

    it "raises error" do
      expect { account.withdraw(50) }.to raise_error(InsufficientFunds)
    end
  end
end

Common Matchers

Equality

expect(x).to eq(y)          # ==
expect(x).to eql(y)         # eql? (type-sensitive)
expect(x).to be(y)          # equal? (identity)

Read the full file on GitHub · 350 lines

Files

What ships with it

54 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.

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.

8d ago First seen · 350 lines · 125 tokens per session scan A 1c70348ca326

Subscribe to this mod's changes

rspec is a skill published in the GitHub repository hoblin/claude-ruby-marketplace (37 stars, last pushed today), licensed MIT. It adds 125 tokens to every session and 2,672 once invoked, about $0.0006 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.

Claude Code Languages Ruby Testing Unit testing activerecord ai-tools claude-plugins code-quality developer-productivity

testing

Authoring Ruby/Rails/Grape/Sidekiq tests: request specs, factories, anti-flake. Triggers: "RSpec patterns", "factory setup", "flaky test". Do NOT use for: running tests, executing rspec.

slbug/claude-ruby-grape-rails · 52 tokens

util-function

Creates a well-typed, tested utility function from a description.

berkcangumusisik/claude-code-practices · 15 tokens

rspec-conventions

Rootstrap RSpec conventions. Use when writing, reviewing, or editing RSpec test files (spec//spec.rb, spec/railshelper.rb, spec/spechelper.rb, spec/support//.rb) or factories. Covers describe/context structure, let/subject, matchers, factories, mocking/stubbing, shared examples, and spec types (model, request…

rootstrap/rails_api_base · 82 tokens

ruby

Ruby development guidelines covering idiomatic code style, Ruby 3.x features, testing with RSpec, and best practices for building maintainable Ruby applications.

Mindrally/skills · 32 tokens

rspec

RSpec testing best practices for Ruby and Rails applications, covering test organization, data management, and isolation patterns.

Mindrally/skills · 24 tokens

testunit-skill

Generates Test::Unit tests in Ruby. Classic xUnit-style testing with assert methods and test case classes. Use when user mentions "Test::Unit", "assertequal Ruby", "Ruby test-unit". Triggers on: "Test::Unit", "Ruby test-unit", "assertequal Ruby" (not RSpec).

LambdaTest/agent-skills · 70 tokens

rspec

Getting it into your agent

Wrote this? Show the measurements

What it costs to keep this loaded

Grade A, and why

Nothing flagged

How it starts

RSpec Testing

Quick Reference

Basic Structure

Key Concepts

Writing Good Specs

Use Named Subject for Method Tests

Context Blocks for Different States

Common Matchers

Equality

What ships with it

What this file has done since we first saw it

Other skills, from other repositories

testing

util-function

rspec-conventions

ruby

rspec

testunit-skill