def test_insufficient_funds_2(generate_utxo_pool):
utxo_pool = generate_utxo_pool([])
selection = select_coins(CoinSelectionParams(utxo_pool, 1, 0, 0, 0, 0, 0))
assert selection.outcome == CoinSelection.Outcome.INSUFFICIENT_FUNDS
assert len(selection.outputs) == 0
assert selection.effective_value == 0
assert selection.change_value == 0
def test_makes_slightly_larger_than_dust_change(generate_utxo_pool):
short_term_fee_per_byte = 100
long_term_fee_per_byte = 100
change_output_size_in_bytes = 100
change_spend_size_in_bytes = 100
utxo_pool = generate_utxo_pool([1 * CENT], short_term_fee_per_byte,
long_term_fee_per_byte)
not_input_size_in_bytes = 100
fixed_fee = short_term_fee_per_byte * not_input_size_in_bytes
cost_of_creating_change = short_term_fee_per_byte * change_output_size_in_bytes
cost_of_spending_change = long_term_fee_per_byte * change_spend_size_in_bytes
cost_of_change = cost_of_creating_change + cost_of_spending_change
total_effective_value = sum(output_group.effective_value
for output_group in utxo_pool)
params = CoinSelectionParams(
utxo_pool=utxo_pool,
target_value=total_effective_value - fixed_fee - cost_of_change - 1,
short_term_fee_per_byte=short_term_fee_per_byte,
long_term_fee_per_byte=long_term_fee_per_byte,
change_spend_size_in_bytes=100,
change_output_size_in_bytes=100,
not_input_size_in_bytes=not_input_size_in_bytes)
selection = select_coins(params)
assert selection.outcome == CoinSelection.Outcome.SUCCESS
assert selection.change_value == params.cost_of_change + params.fixed_fee + 1
def test_invalid_spend(generate_utxo_pool):
utxo_pool = generate_utxo_pool([
1 * CENT,
2 * CENT,
3 * CENT,
4 * CENT,
])
selection = select_coins(CoinSelectionParams(utxo_pool, 0, 0, 0, 0, 0, 0))
assert selection.outcome == CoinSelection.Outcome.INVALID_SPEND
assert len(selection.outputs) == 0
assert selection.effective_value == 0
assert selection.change_value == 0
def test_insufficient_funds_after_fees(generate_utxo_pool):
utxo_pool = generate_utxo_pool([10 * CENT])
selection = select_coins(
CoinSelectionParams(
utxo_pool=utxo_pool,
target_value=10 * CENT,
short_term_fee_per_byte=100,
long_term_fee_per_byte=100,
change_spend_size_in_bytes=100,
change_output_size_in_bytes=100,
not_input_size_in_bytes=100,
))
assert selection.outcome == CoinSelection.Outcome.INSUFFICIENT_FUNDS_AFTER_FEES
assert len(selection.outputs) == 0
assert selection.effective_value == 0
assert selection.change_value == 0
def test_success(generate_utxo_pool):
utxo_pool = generate_utxo_pool([
1 * CENT,
2 * CENT,
3 * CENT,
4 * CENT,
])
selection = select_coins(
CoinSelectionParams(utxo_pool=utxo_pool,
target_value=5 * CENT,
short_term_fee_per_byte=100,
long_term_fee_per_byte=100,
change_spend_size_in_bytes=100,
change_output_size_in_bytes=100,
not_input_size_in_bytes=100))
assert selection.outcome == CoinSelection.Outcome.SUCCESS
assert len(selection.outputs) > 0
assert selection.effective_value >= 5 * CENT
assert selection.change_value > 0
def test_does_not_make_dust_change(generate_utxo_pool):
short_term_fee_per_byte = 100
long_term_fee_per_byte = 100
utxo_pool = generate_utxo_pool([1 * CENT], short_term_fee_per_byte,
long_term_fee_per_byte)
not_input_size_in_bytes = 100
fixed_fee = short_term_fee_per_byte * not_input_size_in_bytes
total_effective_value = sum(output_group.effective_value
for output_group in utxo_pool)
selection = select_coins(
CoinSelectionParams(utxo_pool=utxo_pool,
target_value=total_effective_value - fixed_fee - 1,
short_term_fee_per_byte=short_term_fee_per_byte,
long_term_fee_per_byte=long_term_fee_per_byte,
change_spend_size_in_bytes=100,
change_output_size_in_bytes=100,
not_input_size_in_bytes=not_input_size_in_bytes))
assert selection.outcome == CoinSelection.Outcome.SUCCESS
assert selection.change_value == 0
short_term_fee_per_byte = get_short_term_fee_rate(False)
# 2.3.2 Get long term fee rate per byte
# Sadly, I haven't found any public API's exposing this information
# If you find one or make one yourself, let me know! Would be a cool project.
# Otherwise, it's reasonable to come up with some heuristic method for your app
# Lacking better options, it's okay to use short_term_fee_per_byte,
# though this will cause inefficiencies when short_term_fees are anomalously low or high
long_term_fee_per_byte = short_term_fee_per_byte
# 3 At this point we are ready to select coins; suppose we want to spend 150000 satoshis
target_value = 150000
coin_selection = select_coins(
CoinSelectionParams(utxo_pool, target_value, short_term_fee_per_byte,
long_term_fee_per_byte, change_output_size_in_bytes,
change_spend_size_in_bytes, not_input_size_in_bytes))
# 4 Based on the CoinSelection.Outcome, you can raise different exceptions
# or surface different error text to your UI or whatever
if coin_selection.outcome != CoinSelection.Outcome.SUCCESS:
raise Exception("Coin selection failed")
# 5 Map the coin selection back to your app-specifc class, e.g.
def map_coin_selection_to_utxos(
coin_selection: CoinSelection,
utxo_pool: List[YourUTXOClass]) -> List[YourUTXOClass]:
selected_utxos = []
for selected_coin in coin_selection.outputs:
selected_utxo = next(utxo for utxo in utxo_pool
