IF + Pasado perfecto + would/could/ might + have + participio pasado
If you hadn't made that mistake, you'd have passed your test.
Si no hubieras cometido ese error, habrías aprobado el test).
If I had seen him, I would have told him about you.
Si lo hubiese visto, le habría contado acerca de ti.
If we had studied harder, we might have passed the test.
Si hubiésemos estudiado más duro, podríamos haber aprobado la prueba.
If I hadn't been so busy, I could have helped you.
Si no hubiese estado tan ocupado, te podría haber ayudado.
If they hadn't drunk so much last night, they wouldn't have felt sick today.
Si no hubiesen tomado tanto anoche, no se habrían sentido enfermos hoy.
If he had worked more, he could have saved more money.
Si él hubiese trabajado más, podría haber ahorrado más dinero.