in packages/jest-mock/src/index.ts [446:473]
function isReadonlyProp(object: unknown, prop: string): boolean {
if (
prop === 'arguments' ||
prop === 'caller' ||
prop === 'callee' ||
prop === 'name' ||
prop === 'length'
) {
const typeName = getObjectType(object);
return (
typeName === 'Function' ||
typeName === 'AsyncFunction' ||
typeName === 'GeneratorFunction' ||
typeName === 'AsyncGeneratorFunction'
);
}
if (
prop === 'source' ||
prop === 'global' ||
prop === 'ignoreCase' ||
prop === 'multiline'
) {
return getObjectType(object) === 'RegExp';
}
return false;
}