What is the legal test for a sole shareholder of a corporation?

One starts with Salomon v. Salomon [1897] A.C. 22 which established the principle that the owner of all the shares of a corporation and the corporation are separate legal entities. The logical progression from this principle is that a sole shareholder can enter into contractual relations with his or her company. This is an accepted fact of commercial reality (or, if you will, commercial unreality). One can sell to one's company, buy from one's company, and lease to or from one's company. And one can be an employee of one's own company. I understand it to be generally accepted that a meeting of the minds is an essential ingredient in a contract. One might wonder how there can be a meeting of the minds when we have only one mind - in essence, an identity or fusion of minds. This seems, however, to bother no one.