The common idea of good faith and fair dealing is normally used when there are technical excuses for a breach of contract or specific wording. This principle may be used in different occasions such as fraud (McClain v Octagon Plaza), question of fact (Shah v Cover-it, Inc), unfair and unjust enrichment (Stainbrook v Low) and occasions such as reciprocal duties (Smith v. City and County of San Francisco).
When the question in common law is weather a contract is valid or voidable, the question of breach of contract comes to play. In different occasions such as oral contracts (Jannusch v Naffziger), fraud (McClain v Octagon Plaza), having a minor sign a contract(Yale Diagnostic Radiology v Estate of Harun Fountain) or simply making change at the bank(Barfield v Commerce Bank N. A.)a contract may be binding, breached, it may not be a contract or may be voided.
One of the most important principles in any common law case is the way a contract is performed and applied. The way agreements and rulings are performed and come to a conclusion. Many times a case may not be able to go to court, a decision in weather arbitration is needed or enforced has a heavy change in the final conclusion to the contract. In many cases, court will need to choose while parts of a contract are arbitrariable or not (NCR Corp v Korala Associates Ltd.) or simply lawful to be enforced(Simpson v MSA of Myrtle Beach