Failure to follow K terms is breach. Calculate remedy by π's loss not ∆'s gain
Hawkins v McGee
The hairy hand case- What is said should be accepted at face value. Promises or Guarantees should be upheld to face value of oral agreement.
Bayliner Marine v Crow
Expressed warranties should be accepted for face value but mere opinions or commendations of a sellers product are not expressed warranties and thus are not bases for enforcement.