vitest-expect-typeof

Vitest expectTypeOf API

Deprecated: toMatchTypeOf

The toMatchTypeOf() matcher has been deprecated in Vitest's expectTypeOf API.

Do not use:

expectTypeOf(plan).toMatchTypeOf<Plan<Row>>();

Use toExtend() instead

Use toExtend() to verify that a type extends or matches another type:

Correct usage:

expectTypeOf(plan).toExtend<Plan<Row>>();

When to use toExtend() vs toEqualTypeOf()

• toExtend<T>(): Verifies that the type extends T (allows subtypes). Use when checking that a value's type matches or is a subtype of the expected type.
• toEqualTypeOf<T>(): Verifies exact type equality. Use when checking for exact type matches.

For most cases where you're verifying that a plan or object has the correct type structure, toExtend() is the appropriate choice.

Anti-pattern: Manual type checks with conditional types

Do not use manual type checking patterns with conditional types:

// ❌ WRONG: Manual type check pattern
const _textTypeIdCheck: TextTypeId extends 'pg/text@1' ? true : false = true;
const _intTypeIdCheck: IntTypeId extends 'pg/int4@1' ? true : false = true;

Use Vitest's expectTypeOf instead:

// ✅ CORRECT: Use Vitest type helpers
expectTypeOf<TextTypeId>().toEqualTypeOf<'pg/text@1'>();
expectTypeOf<IntTypeId>().toEqualTypeOf<'pg/int4@1'>();

The manual pattern creates unnecessary variables and is less readable. Vitest's expectTypeOf provides clear, declarative type assertions that integrate with the test framework.