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Vitest · supabase | DecimalAI

supabase/vitest

NewSkillScoreMaintained

Vitest API and config reference (Jest-compatible) — mocking with vi.*, spies, fake timers, coverage configuration, fixtures, snapshots, and test filtering. Use for Vitest API and configuration questions anywhere in the monorepo; for Studio-specific test strategy and component-test setup, start with studio-testing and studio-mock-api-tests.

Testingby supabase

Links this skill to your agents and keeps it current with the author’s updates.

Automatic

QA & Test Engineering pack

1 · One-time — install the CLI (docs ↗)

pip install decimalai

2 · Get the skill — writes .claude/skills/supabase-vitest/SKILL.md

decimalai skills pull supabase-vitest --out .claude/skills/

No CLI? Get the same file — curl · raw file

curl -fsSL --create-dirs -o .claude/skills/supabase-vitest/SKILL.md https://app.decimal.ai/s/supabase-vitest/SKILL.md

Raw file: /s/supabase-vitest/SKILL.md ↗ · machine-readable summary at /s/supabase-vitest.json ↗

In productionGlobal

how this skill behaves on real traffic · last 30 days

No production data for this skill yet — usage numbers appear here once agents start running it.

Anonymized aggregate across every org using this skill — proof from real production use, not a demo.

Does this skill help? · Benchmark: with vs. withoutsign in to run this on your agents

23 test cases from the publisher’s eval.yaml · each run twice on gemini-3.6-flash — with the skill injected, then without · last run 12h ago

No measurable change+26% tokens0% turns96% of whole cases pass with skill (22/23)

Test case	Without → With	Effect	Δ tokens	Δ turns
case-15	✗→✓	▲ Improved	4%	0%
case-19	✗→✓	▲ Improved	-39%	0%
case-11	✓→✗	▼ Worse	17%	0%
case-01	✓→✓	＝ Same ✓	31%	0%
case-02	✓→✓	＝ Same ✓	145%	0%

Showing 5 of 23 cases

SkillSafety

✓ 3 of 3 passed

Code scan15 of 15 checks clean

0 critical · 0 warning · 0 info — scanner v5 — 8/31/2026

live_secretremote_code_executionreverse_shelldata_exfiltrationssrf_metadataagent_snoopinganti_refusaldestructive_commandsobfuscated_unicodeunicode_homoglyphopaque_blobsuspicious_urltool_overreachtrigger_abuseprompt_injection_phrasing

IntentSafe

LLM judge · does the skill do what it claims

ContentClean

LLM judge · policy & harmful-content review

Source

Imported

supabase / supabase

.agents/skills/vitest/SKILL.md

View on GitHub ↗

License Apache-2.0Imported 8/31/2026Version v1Bundled 16 files

Skill contents

references/

SKILL.md

Vitest is a next-generation testing framework powered by Vite. It provides a Jest-compatible API with native ESM, TypeScript, and JSX support out of the box. Vitest shares the same config, transformers, resolvers, and plugins with your Vite app.

Key Features:

Vite-native: Uses Vite's transformation pipeline for fast HMR-like test updates
Jest-compatible: Drop-in replacement for most Jest test suites
Smart watch mode: Only reruns affected tests based on module graph
Native ESM, TypeScript, JSX support without configuration
Multi-threaded workers for parallel test execution
Built-in coverage via V8 or Istanbul
Snapshot testing, mocking, and spy utilities

> The skill is based on Vitest 3.x, generated at 2026-01-28.

Core

| Topic | Description | Reference | | ------------- | --------------------------------------------------------------- | -------------------------------------------- | | Configuration | Vitest and Vite config integration, defineConfig usage | core-config | | CLI | Command line interface, commands and options | core-cli | | Test API | test/it function, modifiers like skip, only, concurrent | core-test-api | | Describe API | describe/suite for grouping tests and nested suites | core-describe | | Expect API | Assertions with toBe, toEqual, matchers and asymmetric matchers | core-expect | | Hooks | beforeEach, afterEach, beforeAll, afterAll, aroundEach | core-hooks |

Features

| Topic | Description | Reference | | ------------ | -------------------------------------------------------------- | ---------------------------------------------------------- | | Mocking | Mock functions, modules, timers, dates with vi utilities | features-mocking | | Snapshots | Snapshot testing with toMatchSnapshot and inline snapshots | features-snapshots | | Coverage | Code coverage with V8 or Istanbul providers | features-coverage | | Test Context | Test fixtures, context.expect, test.extend for custom fixtures | features-context | | Concurrency | Concurrent tests, parallel execution, sharding | features-concurrency | | Filtering | Filter tests by name, file patterns, tags | features-filtering |

Advanced

| Topic | Description | Reference | | ------------ | ------------------------------------------------------- | ------------------------------------------------------------ | | Vi Utilities | vi helper: mock, spyOn, fake timers, hoisted, waitFor | advanced-vi | | Environments | Test environments: node, jsdom, happy-dom, custom | advanced-environments | | Type Testing | Type-level testing with expectTypeOf and assertType | advanced-type-testing | | Projects | Multi-project workspaces, different configs per project | advanced-projects |

Illustrative Want to see what supabase/vitest would put in front of your model? Preview the rendered body and check its trigger phrases — no LLM call, no signup.

Latest benchmark · publisher runVerified

9/27/2026, 05:55 UTC · 23 cases

Lift

50% vs 50%

Agent turns

1.0 vs 1.0

Tokens

+26%

2,103.7 vs 1,668.78

fail → pass · 2pass → pass · 20pass → fail · 1

Per-case results (23)

Case	Status	Duration (ms)			Turns			Tokens			Tool calls
Case	Status	Without	With	Δ	Without	With	Δ	Without	With	Δ	Without	With	Δ
case-01 I am writing unit tests for a TypeScript ESM service in a Vite application. I need to mock the external module `axios` before it gets imported by the module under test. In Jest, I used `jest.mock('axios')`. How should I perform module mocking and hoisted variable declaration in Vitest?	pass→pass	13,001	11,629	-11%	1	1	0%	2,383	3,122	+31%	0	0	—
case-02 I need to spy on the `fetchData` method of a `userService` object in a TypeScript test file without replacing the implementation entirely, but tracking call arguments. What Vitest utility object and method should be used?	pass→pass	4,054	5,800	+43%	1	1	0%	604	1,482	+145%	0	0	—
case-03 In a JavaScript web application test, I have a delay function using `setTimeout`. I want to mock global timers and advance time by 1000 milliseconds to trigger the callback synchronously. Which Vitest utility handles fake timer initialization and advancing?	pass→pass	6,446	6,827	+6%	1	1	0%	1,080	1,790	+66%	0	0	—
case-04 I am building a TypeScript library and want to write tests that verify type definitions at compile time—specifically checking that a utility type returns `string` and asserting exact type compatibility without running runtime expectations. What built-in Vitest utilities perform type assertions?	pass→pass	14,377	9,780	-32%	1	1	0%	2,250	2,575	+14%	0	0	—
case-05 In a test suite, I want to define reusable test fixtures like a pre-authenticated database client passed directly into the test callback parameter using context extension, rather than declaring global `let` variables in `beforeEach`. What method on `test` should be used to define custom fixtures?	pass→pass	6,927	6,166	-11%	1	1	0%	817	1,699	+108%	0	0	—
case-06 I have 10 independent async API integration tests in a single file that can run in parallel to save execution time. How do I configure test execution for those specific test cases using the Vitest test API?	pass→pass	11,196	8,842	-21%	1	1	0%	1,970	2,278	+16%	0	0	—
case-07 I am setting up unit testing for a Vite project and want to configure test options alongside Vite config using TypeScript. I also want code coverage using the native V8 engine. What function and package should be imported for the configuration file, and what coverage provider option should be set?	pass→pass	7,278	5,610	-23%	1	1	0%	1,063	1,625	+53%	0	0	—
case-08 I am testing React UI components that rely on DOM APIs like `document.createElement`. By default Vitest runs in Node.js. What test environment options can be configured in Vitest for simulated browser DOM execution?	pass→pass	11,202	10,018	-11%	1	1	0%	1,865	2,551	+37%	0	0	—
case-09 I want to assert that an object emitted by an event contains a specific `id` property with value `'123'` and any string for `timestamp`, without requiring exact equality on all other properties. How should asymmetric matchers be written using the Vitest assertion API?	pass→pass	9,346	7,694	-18%	1	1	0%	1,640	2,047	+25%	0	0	—
case-10 I want to test that a rendered component structure or JSON output matches a previously saved reference file on disk, or alternatively maintain the snapshot inline inside the test file. What matchers does Vitest provide for snapshot testing?	pass→pass	14,135	11,644	-18%	1	1	0%	2,182	2,586	+19%	0	0	—
case-11 I have a monorepo with a frontend package needing DOM environment and a backend package needing Node.js environment. How does Vitest handle configuring multi-project workspaces with distinct configurations in a single run?	pass→fail	13,487	11,670	-13%	1	1	0%	2,571	3,002	+17%	0	0	—
case-12 In an integration test, an asynchronous state update occurs outside of a promise response. I need to repeatedly poll an assertion until it succeeds or times out within 2 seconds. Which `vi` utility helper simplifies waiting for a condition or assertion?	pass→pass	9,184	4,443	-52%	1	1	0%	1,387	1,525	+10%	0	0	—
case-13 I need to reset a mock database before every single test run in a suite, and clean up global resources once after all tests in the file finish. Which lifecycle hooks from Vitest perform these actions?	pass→pass	5,108	5,784	+13%	1	1	0%	854	1,568	+84%	0	0	—
case-14 I want to execute only the unit test files that match the pattern `auth` or run tests with a specific file filter from the command line without modifying any source files. How is filtering done using the Vitest CLI?	pass→pass	9,758	8,426	-14%	1	1	0%	1,536	2,090	+36%	0	0	—
case-15 I have a test that should only run when an environment variable `ENABLE_INTEGRATION` is set to `true`. If not set, the test runner should mark the test as skipped rather than failing or running it. What test API modifier or conditional skip method should be used?	fail→pass	9,866	6,937	-30%	1	1	0%	1,828	1,909	+4%	0	0	—
case-16 How can I group related tests for a `UserService` module into logical sub-suites in Vitest, and what hook or grouping API is available?	pass→pass	14,057	9,901	-30%	1	1	0%	2,405	2,709	+13%	0	0	—
case-17 I need to pass a dummy callback function into a component prop and assert how many times it was called and what arguments it received. What `vi` utility creates a mock function in Vitest?	pass→pass	6,296	6,038	-4%	1	1	0%	997	1,783	+79%	0	0	—
case-18 I am configuring GitHub Actions CI with 4 parallel runner nodes. I want Vitest to automatically partition the test suite into 4 execution shards so runner 1 executes shard 1/4, runner 2 executes shard 2/4, and so on. What CLI option does Vitest provide for this?	pass→pass	5,403	6,468	+20%	1	1	0%	883	1,641	+86%	0	0	—
case-19 When writing custom runner extensions or working inside test fixtures in Vitest, how can a fixture access the bound `expect` instance scoped specifically to the current running test context?	fail→pass	22,126	9,127	-59%	1	1	0%	3,487	2,135	-39%	0	0	—
case-20 I am writing a test where I need to spy on global `console.log` during test execution and restore the original implementation after the test completes. Which `vi` helper function restores all spied and mocked implementations to their original state?	pass→pass	7,600	13,677	+80%	1	1	0%	1,216	1,860	+53%	0	0	—
case-21 I am writing a full browser E2E test using Playwright. I need to navigate to `https://example.com`, locate a button with text 'Submit' using `page.getByRole`, click it, and wait for navigation. Provide the Playwright test code.	pass→pass	8,757	9,085	+4%	1	1	0%	1,402	2,159	+54%	0	0	—
case-22 I have a legacy Webpack 5 application using Babel and `jest-transform-stub` with `babel-jest` in `jest.config.js`. How do I configure `jest.config.js` `transform` regex map for `.tsx` files using `ts-jest`?	pass→pass	15,411	12,265	-20%	1	1	0%	2,500	2,389	-4%	0	0	—
case-23 I have a slow SQL query in my PostgreSQL database running on Supabase: `SELECT * FROM orders WHERE user_id = $1 AND status = 'pending'`. How can I create a composite B-tree index in PostgreSQL to optimize this query?	pass→pass	8,456	6,444	-24%	1	1	0%	1,462	1,860	+27%	0	0	—

These cases were also screened by the skill’s intent / safety pass.See the Trust review ↗Reproduce this benchmark in Colab ↗

How this skill was measured

DecimalAI ran this skill against gemini-3.6-flash twice over the same eval suite — once with the skill loaded and once without — and compared the two runs case by case. 23 cases were attempted. The headline lift of 0 percentage points is the difference between those two pass rates over the 23 comparable cases. 1 case got worse with the skill loaded, and it is included in that figure.

Model measured: gemini-3.6-flash
Graded by: gemini-3.6-flash
Grading method: judged
Verification: verified
Pass rate without the skill: 50%
Pass rate with the skill: 50%
Cases attempted: 23
Cases counted toward lift: 23
Cases that regressed: 1
Skill version measured: v1
Run completed: 9/27/2026, 05:55 UTC

Measured example — same prompt, with vs. without the skill · from the benchmark run · case case-15

Prompt

I have a test that should only run when an environment variable `ENABLE_INTEGRATION` is set to `true`. If not set, the test runner should mark the test as skipped rather than failing or running it. What test API modifier or conditional skip method should be used?

Without the skill loaded, the model failed this case. With it loaded, the same prompt on the same model passed. This is one improved case from the latest verified run; every case, including any that regressed, is in the table above.

Show both answers

SkillScore blends 4 signalsno signals yet

BenchmarkRun a verified benchmark with positive lift

Live evalNeeds ≥10 evaluated traces in 30 days

AI ratingNeeds ≥10 rated traces

AdoptionNeeds ≥10 serves across ≥2 orgs in 30 days

No signals yet — run a benchmark or collect evaluated traces to earn a score.

Verified on gemini-3.6-flash · re-tested today

Other measured skills in the registry, with their headline benchmark lift.