def test_coin_amount_fail():
coin = Coin(amount=-5000, denom="uband")
with pytest.raises(NegativeIntegerError,
match="Expect amount more than 0"):
coin.validate()
def test_coin_success():
coin = Coin(amount=5000, denom="uband")
assert coin.as_json() == {"amount": "5000", "denom": "uband"}
assert coin.validate() == True