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# Vitest integration

The `@mastra/evals/vitest` module integrates [`runEvals`](https://mastra.ai/reference/evals/run-evals) with [Vitest](https://vitest.dev/) so evaluations behave like regular tests. Fluent assertions fail the test when the eval doesn't pass, and a reporter prints a score table in the runner output.

To use it, install `@mastra/evals` and `vitest` (version 3 or 4):

```bash
npm install @mastra/evals vitest
```

## Configuring Vitest

Register the reporter and matchers in `vitest.config.ts`:

```typescript
import { defineConfig } from 'vitest/config'
import { MastraEvalsReporter } from '@mastra/evals/vitest'

export default defineConfig({
  test: {
    reporters: ['default', new MastraEvalsReporter()],
    setupFiles: ['@mastra/evals/vitest/setup'],
  },
})
```

The setup file registers the custom matchers on `expect`. Alternatively, call `registerEvalMatchers()` from `@mastra/evals/vitest` in your own setup file.

## Asserting on a dataset with `expectEvals`

`expectEvals` runs a `runEvals` evaluation inside a regular `test()` and asserts a minimum pass rate. It accepts the same configuration as `runEvals`: a `target` agent or workflow, `data` items, and `scorers`, `gates`, or thresholds. Gates score each item pass/fail, so `toPass(0.8)` requires at least 80% of items to pass every gate. Scorer thresholds still compare the average score across items and must pass regardless of the rate:

```typescript
import { test } from 'vitest'
import { expectEvals } from '@mastra/evals/vitest'
import { capitalsAgent } from './capitals-agent'
import { containsGroundTruth } from '../scorers'
import { createKeywordCoverageScorer } from '@mastra/evals/scorers/prebuilt'

test('capitals agent answers with the expected city', { timeout: 60_000 }, async () => {
  await expectEvals({
    target: capitalsAgent,
    data: [
      { input: 'What is the capital of France?', groundTruth: 'Paris' },
      { input: 'What is the capital of Japan?', groundTruth: 'Tokyo' },
      { input: 'What is the capital of Australia?', groundTruth: 'Canberra' },
    ],
    gates: [containsGroundTruth],
    scorers: [{ scorer: createKeywordCoverageScorer(), threshold: 0.4 }],
  }).toPass(0.8)
})
```

`toPass()` without an argument requires every item to pass every gate. Always await the assertion: it resolves with the full `RunEvalsResult` for further checks and attaches the run's scores to the current test so `MastraEvalsReporter` displays them.

LLM-backed evals are far slower than Vitest's default 5-second timeout, so pass a per-test `timeout` (or set `testTimeout` in the Vitest config).

## Matrix testing with `expectEval`

`expectEval` is the single-item variant: `data` is one item instead of an array. Combine it with `test.for` (or `test.each`) to get one test (and one reporter entry) per data item instead of one aggregated result per dataset:

```typescript
import { test } from 'vitest'
import { expectEval } from '@mastra/evals/vitest'
import { capitalsAgent } from './capitals-agent'
import { containsGroundTruth } from '../scorers'

test.for([
  { input: 'What is the capital of France?', groundTruth: 'Paris' },
  { input: 'What is the capital of Japan?', groundTruth: 'Tokyo' },
  { input: 'What is the capital of Australia?', groundTruth: 'Canberra' },
])('capitals agent: $input', { timeout: 60_000 }, async item => {
  await expectEval({
    target: capitalsAgent,
    data: item,
    gates: [containsGroundTruth],
  }).toPass()
})
```

Each item passes or fails independently, so a single regression shows up as one failing test instead of a lowered aggregate pass rate.

## Asserting on results with matchers

For finer-grained control, call `runEvals` directly inside a regular `test()` and use the custom matchers on the result:

```typescript
import { test, expect } from 'vitest'
import { runEvals } from '@mastra/core/evals'
import { supportAgent } from './support-agent'
import { relevancyScorer, noRefusalScorer } from '../scorers'

test('support agent quality', { timeout: 60_000 }, async () => {
  const result = await runEvals({
    target: supportAgent,
    data: [{ input: 'How do I update my payment method?' }],
    scorers: [relevancyScorer],
    gates: [noRefusalScorer],
  })

  expect(result).toHaveVerdict('passed')
  expect(result).toPassGates()
  expect(result).toHaveScoreAbove('relevancy', 0.7)
})
```

Available matchers:

- `toHaveVerdict(verdict)`: asserts the run's verdict (`"passed"`, `"scored"`, or `"failed"`).
- `toHaveScoreAbove(scorerName, min)` / `toHaveScoreBelow(scorerName, max)`: asserts a scorer's average score. Categorized scorer configs use dot-paths, for example `"agent.my-scorer"` or `"steps.step-1.my-scorer"`.
- `toPassGates()`: asserts all gates passed. Fails when no gates were configured.
- `toPassThresholds()`: asserts all scorer thresholds passed. Fails when no thresholds were configured.

## Reading the reporter output

`MastraEvalsReporter` prints a score table for every eval test after the run completes:

```text
Mastra Evals

✓ capitals agent answers with the expected city (3 items)
   contains-ground-truth (gate)                    1.0  ✓
   keyword-coverage-scorer (threshold: min 0.4)    1.0  ✓

 Eval runs: 1 (1 passed)
```

Each entry shows the run's verdict, gates, thresholds, and the average score per scorer. The reporter reads the metadata that `expectEval`/`expectEvals` attach to `task.meta.mastraEval`, so it works with parallel test files and any test that populates that field.

## Rate limits and concurrency

Vitest runs test files in parallel, and `runEvals` accepts its own `concurrency` option, so total LLM traffic is multiplied across both. If you hit provider rate limits, lower `concurrency` in your eval options or set `fileParallelism: false` in the Vitest config.