garrytan/resend_robot

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Latest recorded source activity: March 17, 2026 at 23:24

SkillsMP catalog refreshed: October 26, 2026 at 11:37

skills collected: 2

GitHub stars: 14
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# Resend Robot **letter_opener for the [Resend](https://resend.com) gem.** Intercepts Resend API calls in development, stores emails as JSON on disk, and provides a web UI to browse, preview, and simulate replies. Production code runs unchanged — same pipeline in dev and prod. ## Installation Add to your Gemfile: ```ruby gem "resend_robot", group: :development ``` Run `bundle install`, then run the install generator: ```bash bin/rails generate resend_robot:install ``` This creates: - `config/initializers/resend_robot.rb` — configuration (reply domain, mount path, etc.) - `.claude/skills/resend-robot-read/skill.md` — Claude skill for reading dev emails - `.claude/skills/resend-robot-send/skill.md` — Claude skill for simulating inbound emails The generator is safe to re-run — it will ask before overwriting existing files. Resend Robot automatically: - Installs shims that intercept `Resend::Emails.send`, `Resend::Batch.send`, etc. - Sets a dummy API key so `Resend::Mailer` doesn't raise - Injects routes at `/dev/email` for the web UI - Provides rake tasks for CLI interaction ## Web UI Visit `http://localhost:3000/dev/email` to browse your dev mailbox: - **Outbox** — all intercepted emails, newest first, with search/filter - **Preview** — inline HTML rendering with sanitization (no iframes) - **Reply** — simulate inbound email through your real webhook pipeline ## Configuration ```ruby # config/initializers/resend_robot.rb ResendRobot.configure do |config| config.reply_domain = "reply.example.com" # required for inbound simulation config.webhook_path = "/webhooks/resend" # default config.dev_port = 3000 # auto-detected from action_mailer config.open_in_browser = true # auto-open emails in browser config.mount_path = "/dev/email" # change to mount UI elsewhere end ``` ### Bypass the shim To send real emails via the Resend API in development: ```bash RESEND_IN_DEV=1 bin/dev ``` ### Suppress auto-open ```bash OPEN_EMAILS=0 bin/dev ``` ## Test Helpers Resend Robot includes Minitest assertions for verifying emails in your test suite: ```ruby class UserSignupTest < ActiveSupport::TestCase include ResendRobot::TestHelper test "sends welcome email on signup" do clear_emails User.create!(email: "alice@example.com") assert_email_sent_to "alice@example.com" assert_email_sent_to "alice@example.com", subject: /Welcome/ assert_equal 1, emails_sent.count assert_equal "Welcome", last_email[:subject] end test "does not send email without signup" do clear_emails assert_no_emails_sent end end ``` ### Available assertions | Method | Description | |--------|-------------| | `clear_emails` | Clear all stored emails (call in setup) | | `emails_sent` | All outbound emails as symbol-keyed hashes | | `last_email` | Most recent outbound email | | `assert_email_sent_to(addr, subject: nil)` | Assert email was sent to address, optionally matching subject (String or Regexp) | | `assert_no_emails_sent` | Assert no emails were sent | ## JSON API For E2E tests (Playwright, Capybara), the web UI also serves JSON: ``` GET /dev/email.json → array of all emails GET /dev/email/:id.json → single email object ``` ## Claude Skills The install generator adds two [Claude Code](https://claude.ai/claude-code) skills: | Skill | Description | |-------|-------------| | `/resend-robot-read` | List, search, and inspect dev emails from the CLI | | `/resend-robot-send` | Simulate inbound emails through your webhook pipeline | These let Claude interact with your dev mailbox conversationally: - "Show me the last email sent" → runs `/resend-robot-read` - "Simulate a reply to the welcome email" → runs `/resend-robot-send` Skills are plain markdown files in `.claude/skills/` — customize them for your app (e.g., add app-specific models or webhook details). ## Rake Tasks ```bash bin/rails resend_robot:outbox # List recent emails bin/rails resend_robot:show[rl_xxx] # Show specific email bin/rails resend_robot:receive[from,to,subject,body] # Simulate inbound bin/rails resend_robot:reply[index,body] # Reply to Nth most recent bin/rails resend_robot:clear # Clear all emails ``` ## How It Works Resend Robot monkey-patches 5 Resend gem methods in development: | Method | Shimmed behavior | |--------|-----------------| | `Resend::Emails.send` | Stores email as JSON on disk | | `Resend::Batch.send` | Stores each email individually | | `Resend::Emails::Receiving.get` | Returns stored inbound email | | `Resend::Emails::Receiving::Attachments.get` | Returns stub attachment | | `Resend::Webhooks.verify` | Returns `true` (bypasses signature validation) | Your production code (mailers, webhook controllers, inbound email handlers) runs unchanged. The shim operates at the Resend gem boundary — everything downstream is real. ## vs letter_opener | | letter_opener | Resend Robot | |-|---------------|--------------| | Works with | SMTP delivery | Resend API client | | Storage | Rendered HTML files | JSON (preserves all metadata) | | Inbound simulation | No | Yes — POSTs to your real webhook endpoint | | Test helpers | No | Yes (`assert_email_sent_to`, etc.) | | JSON API | No | Yes (for E2E tests) | | Web UI | Basic | Search, filter, reply simulation | ## Requirements - Ruby >= 3.1 - Rails >= 7.0 - [resend](https://github.com/resendlabs/resend-ruby) gem >= 1.0 ## Documentation - [ARCHITECTURE.md](ARCHITECTURE.md) — System design, component overview, data flow diagrams - [CONTRIBUTING.md](CONTRIBUTING.md) — Dev setup, running tests, project structure - [CHANGELOG.md](CHANGELOG.md) — Release history - [TODOS.md](TODOS.md) — Planned future work ## License MIT

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Skills in this repository

Software Developers Software Quality Assurance Analysts & Testers

2 occupation categories · 100% classified

skill

occupation

description

updated

resend-robot-read

Software Developers

Read dev mailbox. Lists sent emails, shows email details, searches by recipient or subject. Uses Resend Robot's local Resend shim.

2026-03-17

resend-robot-send

Software Quality Assurance Analysts & Testers

Simulate receiving an inbound email in dev. Sends through the app's webhook pipeline via Resend Robot's local shim.

2026-03-17

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