What is the difference between el "examen fue largo" and "el examen estuvo largo"?
This really boils down to the difference in
Ser vs Estar
Fue largo el examen
just means... it was a long test
Estuvo largo el examen
means you're telling a story involving this long test. Consider these English differences.
How was the test? It was a long test.
Yesterday, I had to pick up my little sister after taking a test. It was a long test, and I was constantly distracted by the pretty teacher.
The first example is very passive, while the second example really emphasizes the length of the test.
Ayer assistía a mi clase y me sorprendió que hubo un examen. Estuvo un examen largo.
It can also mean that the test was unusually long