Implementar clase Operation
Implementar tests de la clase Operations
Incluir clases hijas concretas de Operation
Implementar clase Operations
Move classes to their correct folder
Implementar test de multiplicación
Incluir reset() en el test de Operation
Implementar Multiplication
Implementar tests de Summation y Substraction
Rename Subtraction to substraction
Update tests
Add inheritance to tests
Add AllTests. Fix total() in Operations
Implement Summation and Substraction
Refactor OperationsTest