def test_non_listed_guest():
# a guest must be in the list of composers
with pytest.raises(ValueError):
list(operas_both_at_premiere("dvorak", "verdi"))
def test_wagner_verdi():
# materializing to list to support generator as return
wagner_verdi = list(operas_both_at_premiere("wagner", "verdi"))
assert len(wagner_verdi) == 10
assert "Otello" not in wagner_verdi
def test_non_listed_composer():
with pytest.raises(ValueError):
list(operas_both_at_premiere("verdi", "dvorak"))
def test_beethoven_mozart():
beethoven_mozart = list(operas_both_at_premiere("beethoven", "mozart"))
assert len(beethoven_mozart) == 5
assert "Apollo and Hyacinth" not in beethoven_mozart
def test_wagner_beethoven():
wagner_beethoven = list(operas_both_at_premiere("wagner", "beethoven"))
assert len(wagner_beethoven) == 0
def test_beethoven_wagner():
beethoven_wagner = list(operas_both_at_premiere("beethoven", "wagner"))
assert len(beethoven_wagner) == 0
def test_verdi_wagner():
verdi_wagner = list(operas_both_at_premiere("verdi", "wagner"))
assert len(verdi_wagner) == 11
# premiere after Wagner's death (composed in 1833)
assert "The Fairies" not in verdi_wagner