This tutorial is concerned with repudiation of contracts. There are two ways to repudiate (see Restatement (Second) of Contracts ยง 250).
The first way: Make a statement that one is going to materially breach a contractual obligation. Call this a repudiating statement. The statement must be definite and unequivocal.
The second way: Voluntarily do something that means (or at least appears to mean) that one will materially breach a contractual obligation. Call this a repudiating action.
Hochster v. De La Tour illustrates a repudiating statement.