key undefined when using validateAt

[yuenhy]

In my actual implementation code, I use testContext from validate to retrieve key, which enables me to access something in the context object.
However when writing unit tests, I can't access the key key with validateAt.

const nameValidation = yup.string().test('isOk', ({label}) => `${label} is not ok`, (value, testContext) => {
    const field = testContext.options.key;
    return field !== undefined;
});
const accountSchema = yup.object({
    name: nameValidation,
});

const account = {
    name: 'schemer',
};

accountSchema.validate(account).then(console.log);
// "name"
accountSchema.validateAt('name', account).catch(console.log);
// undefined

Am I doing something wrong?
(I hope not to parse path... but let me know )