def test_can_measure_how_much_available():
b = ByteStream()
assert b.available() == 0
b.write(b"hello")
assert b.available() == 5
b.read(2)
assert b.available() == 3
b.read(2)
assert b.available() == 1
b.read(2)
assert b.available() == 1
b.read(1)
assert b.available() == 0
def test_reading_nothing_does_nothing():
b = ByteStream()
b.write(b"hello")
assert b.available() == 5
b.read(0)
assert b.available() == 5
