def test_drop():
assert ZZ.drop(x) == ZZ
assert ZZ[x].drop(x) == ZZ
assert ZZ[x, y].drop(x) == ZZ[y]
assert ZZ.frac_field(x).drop(x) == ZZ
assert ZZ.frac_field(x, y).drop(x) == ZZ.frac_field(y)
assert ZZ[x][y].drop(y) == ZZ[x]
assert ZZ[x][y].drop(x) == ZZ[y]
assert ZZ.frac_field(x)[y].drop(x) == ZZ[y]
assert ZZ.frac_field(x)[y].drop(y) == ZZ.frac_field(x)
Ky = FiniteExtension(Poly(x**2-1, x, domain=ZZ[y]))
K = FiniteExtension(Poly(x**2-1, x, domain=ZZ))
assert Ky.drop(y) == K
raises(GeneratorsError, lambda: Ky.drop(x))
