When an employer says, "Either you resign or we'll fire you", that's constructive termination.
Constructive resignation occurs when an employee "engages in conduct inconsistent with the continuation of the employee-employer relationship." For example, if you were to burn down your place of work such that it was impossible for you to continue performing your job, your employer could deem that a "constructive resignation", and you wouldn't have a prayer of claiming wrongful termination.

