Function expectToEqual

expectToEqual<T>(arg: unknown, expected: T): asserts arg is T

Equivalent to calling vitest.expect(arg).toEqual(expected) while also asserting arg to be the type of expected.

Type Parameters

T
The type of arg.

Parameters

arg: unknown
The variable to be asserted.
expected: T
The expected value.

Returns asserts arg is T

undefined.

Assert

arg is T.

Example: Basic

const parsed = JSON.parse('{"key": "val"}')
expectToEqual(parsed, {key: "val"} as const);
// parsed is of type {readonly key: "val"}.

Example: A more practically meaningful scenario

const inputs = ['{"key1": "val1"}', '{"key2": "val2"}'];
const expectedResults = [{ key1: "val1" }, { key2: "val2" }] as const;
inputs.forEach((input, index) => {
  const parsed = JSON.parse(input);
  expectToEqual(parsed, expectedResults[index]);
  // parsed is of type { readonly key1: "val1"; } | { readonly key2: "val2"; }
});