Write tests for the validateEmail function, which takes the email string and returns true for valid email, and false for invalid.

An email is a string (a subset of ASCII characters) separated into two parts by @ symbol, a "personal_info" and a domain, that is personal_info@domain.

The personal_info part contains the following ASCII characters.

• English letters (Aa-Zz)

• digits

• characters: - _

• character . ( period, dot or fullstop) provided that it is not the first or last character and it will not come one after the other.

• @ is required

• personal_info and domain can not start with dot .

• double dots are not allowed in personal_info part

• not allowed characters: ! $ % & ' * + / = ? ^ { | } ~

The domain name part contains letters, digits, hyphens, and dots.

The function does not check the uniqueness of the email (it happens during the request to DB) and the length of the email (it made by another function).

Examples:

validateEmail('test@mail.com') === true
validateEmail('t@q.c') === true
validateEmail('false@email') === false

Hint: focus on the most priority and realistic cases, do not focus on edge cases.

Guideline

Read more about Jest expectations