Matchers

LLMAssert provides 5 assertion matchers. All return { pass: boolean, score: number | null, reasoning: string } and support .not negation.

Matcher	What it checks	Score meaning
`toBeGroundedIn`	Every claim is supported by the context	1.0 = fully grounded, 0.0 = fabricated
`toBeFreeOfPII`	No personally identifiable information	1.0 = no PII, 0.0 = definite PII
`toMatchTone`	Matches a described tone/sentiment	1.0 = perfect match, 0.0 = opposite tone
`toBeFormatCompliant`	Conforms to a described structure	1.0 = fully compliant, 0.0 = wrong structure
`toSemanticMatch`	Semantically similar to reference text	1.0 = identical meaning, 0.0 = unrelated

Common patterns

All matchers accept an optional threshold override:

await expect(response).toBeGroundedIn(context, { threshold: 0.9 });

All matchers support .not negation:

await expect(creativeResponse).not.toBeGroundedIn(context);

A null score means the evaluation was inconclusive (judge unavailable) — the test passes rather than producing a false failure.

All matchers use 0.7 as the default threshold. Scores at or above the threshold pass.

Threshold sources (highest priority first):

See Thresholds for detailed guidance on choosing values per matcher.