It is so unclear that most legislatures haven't even attempted to define it. As result we still must resort to the common law to attempt to determine this issue. The ESA definitions of employee and employer are inclusive but not determinative. The permanency test considers the duration of the employment and is usually applied when a person may be paid by one company but is all other respects an employee of another. The important thing to note about all of these tests is that little or no attention is paid to what a written contract between the parties may say or what sort of legal relationship the parties intended to create.
Frustration occurs where the employee dies or is permanently incapacitated.
It can also occur where by some act of God an employer's premises are destroyed. Economic difficulty caused by market forces has never been considered to be frustration of a contract. Cause for dismissal is conduct so as to fundamentally breach the employment contract. Mere incompetence is not usually cause for dismissal unless the employee has been given an opportunity to improve his or her performance. Serious offenses such as dishonesty or failure to attend work without good reason are cause for dismissal without the necessity for progressive discipline.