r-testthat SKILL.md skillA
r-testthat from posit-dev/skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add posit-dev/skills/r-testthat@v1.1Pins v1.1 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- posit-dev/skills
- Path
r-lib/r-testthat/SKILL.md- Versions recorded
- 1
- Latest version
- v1.1, committed Oct 6, 2026
- Size
- 11,202 bytes
- Repository stars
- 556
- License
- MIT
Best practices for writing R package tests with testthat version 3+. Use this skill when writing or organizing tests for an R package or when improving existing tests that use testthat. It covers test structure and expectations, self-sufficient test design, proper cleanup with withr, fixtures, mocking external dependencies, snapshot testing, and BDD-style describe/it patterns.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Testing R Packages with testthat
Modern best practices for R package testing using testthat 3+.
## Initial Setup
Initialize testing with testthat 3rd edition:
```r
usethis::use_testthat(3)
```
This creates `tests/testthat/` directory, adds testthat to `DESCRIPTION` Suggests with `Config/testthat/edition: 3`, and creates `tests/testthat.R`.
## File Organization
**Mirror package structure:**
- Code in `R/foofy.R` → tests in `tests/testthat/test-foofy.R`
- Use `usethis::use_r("foofy")` and `usethis::use_test("foofy")` to create paired files
**Special files:**
- `helper-*.R` - Helper functions and custom expectations, sourced before tests
- `setup-*.R` - Run during `R CMD check` only, not during `load_all()`
- `fixtures/` - Static test data files accessed via `test_path()`
## Test Structure
Tests follow a three-level hierarchy: **File → Test → Expectation**
### Standard Syntax
```r
test_that("descriptive behavior", {
result <- my_function(input)
expect_equal(result, expected_value)
})
```
**Test descriptions** should read naturally and describe behavior, not implementation.
### BDD Syntax (describe/it)
For behavior-driven development, use `describe()` and `it()`:
…Read the whole file at its exact version.
How to install
mdr add posit-dev/skills/r-testthat@sha256:1ab412ca413fa9a1The line at the top of this page pins the label v1.1, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_yjwzwbn6lfh6f747)
3 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 1 version of this file, committed on Oct 6, 2026.
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (11202 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
posit-dev/skills · 556 stars · license MIT · pushed 2026-11-02 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_yjwzwbn6lfh6f747 GET https://markdownregistry.com/api/v1/resolve?ref=posit-dev/skills/r-testthat GET https://markdownregistry.com/api/v1/blob/1ab412ca413fa9a1420e74157af3828218dafe7d15fe560c19b11986264c0d02
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.