amt.py: reimplement CoinAmt.to_unit(), add test

mmgen/amt.py

@@ -65,7 +65,12 @@ class CoinAmt(Decimal, Hilite, InitErrors): # abstract class
 			return cls.init_fail(e, num)
 
 	def to_unit(self, unit):
-		return int(Decimal(self) // getattr(self, unit))
+		if (u := getattr(self, unit)) == self.atomic:
+			return int(Decimal(self) // u)
+		else:
+			return Decimal('{:0.{w}f}'.format(
+				self / u,
+				w = (u/self.atomic).as_tuple().exponent))
 
 	@classmethod
 	def fmtc(cls, *args, **kwargs):
@@ -165,6 +170,7 @@ class BTCAmt(CoinAmt):
 	max_prec = 8
 	max_amt = 21000000
 	satoshi = Decimal('0.00000001')
+	atomic = satoshi
 	units = ('satoshi',)
 
 class BCHAmt(BTCAmt):
@@ -190,6 +196,7 @@ class ETHAmt(CoinAmt):
 	Gwei    = Decimal('0.000000001')
 	szabo   = Decimal('0.000001')
 	finney  = Decimal('0.001')
+	atomic  = wei
 	units   = ('wei', 'Kwei', 'Mwei', 'Gwei', 'szabo', 'finney')
 
 	def toWei(self):

test/modtest_d/ut_amt.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+
+"""
+test.modtest_d.ut_amt: CoinAmt unit tests for the MMGen suite
+"""
+
+from decimal import Decimal
+
+from mmgen.protocol import init_proto
+from mmgen.cfg import Config
+
+from ..include.common import cfg, vmsg
+
+def get_protos(data):
+	return {coin: init_proto(cfg, coin, need_amt=True) for coin in set(d[0] for d in data)}
+
+def test_to_unit(data):
+	protos = get_protos(data)
+	for proto, amt, unit, chk in data:
+		amt = protos[proto].coin_amt(amt)
+		res = amt.to_unit(unit)
+		vmsg(f'  {proto.upper()} {amt.fmt(8)} => {res:<14} {unit}')
+		if '.' in chk:
+			assert res == Decimal(chk), f'{res} != {Decimal(chk)}'
+		else:
+			assert res == int(chk), f'{res} != {int(chk)}'
+	return True
+
+class unit_tests:
+
+	altcoin_deps = ('to_unit_alt',)
+
+	def to_unit(self, name, ut, desc='CoinAmt.to_unit() (BTC)'):
+		return test_to_unit((
+			('btc', '0.00000001', 'satoshi', '1'),
+			('btc', '1.23456789', 'satoshi', '123456789')))
+
+	def to_unit_alt(self, name, ut, desc='CoinAmt.to_unit() (LTC, BCH, ETH, XMR)'):
+		return test_to_unit((
+			('ltc', '0.00000001',           'satoshi', '1'),
+			('ltc', '1.23456789',           'satoshi', '123456789'),
+			('bch', '0.00000001',           'satoshi', '1'),
+			('bch', '1.23456789',           'satoshi', '123456789'),
+			('eth', '1.234567890123456789', 'wei',     '1234567890123456789'),
+			('eth', '1.234567890123456789', 'Kwei',    '1234567890123456.789'),
+			('eth', '1.234567890123456789', 'Mwei',    '1234567890123.456789'),
+			('eth', '1.234567890123456789', 'finney',  '1234.567890123456789'),
+			('eth', '0.000000012345678901', 'Mwei',    '12345.678901'),
+			('eth', '0.000000000000000001', 'Kwei',    '0.001'),
+			('eth', '0.000000000000000001', 'Gwei',    '0.000000001'),
+			('eth', '0.00000001',           'Gwei',    '10'),
+			('eth', '1',                    'Gwei',    '1000000000'),
+			('eth', '1',                    'finney',  '1000'),
+			('xmr', '1',                    'atomic',  '1000000000000'),
+			('xmr', '0.000000000001',       'atomic',  '1'),
+			('xmr', '1.234567890123',       'atomic',  '1234567890123')))