data-guarantee.md

Data Guarantee

A data guarantee is a function that throws an Error if the input doesn't meet whatever specification the data guarantee enforces.

For example:

export function mustBeUuidData(
    input: string,
    onError: OnError
): void {
    if (isUuidData(input)) {
        return true;
    }

    throw onError(new TypeError("input is not a value!!));
}

The key properties of a data guarantee are:

• it is asserting that the input passes a given test, ie that the data it contains is acceptable in some way
• there's no return value, so it doesn't matter if the caller forgets to check it