Make tests always pass by ensuring there is only 1 coinbase utxo to shield

qa/rpc-tests/shieldcoinbase_donation.py

@@ -109,10 +109,6 @@ class ShieldCoinbaseDonationTest (BitcoinTestFramework):
         # sendAmount/donationAmount arithmetic leads to a situation where the
         # exact amount in satoshis must deal with truncation/rounding
 
-        # generate some new coinbase funds
-        rpc.generate(1)
-        self.sync_all()
-
         # shield funds to a new zaddr in this wallet with non-default fee
         fee = 0.00000001 # 1 puposhi fee will lead to some kind of rounding/truncation arithmetic
         response = rpc.z_shieldcoinbase('*', zaddr1, fee, 1, donation)
@@ -120,8 +116,9 @@ class ShieldCoinbaseDonationTest (BitcoinTestFramework):
         print("opid=" + opid)
 
         shieldingValue = response['shieldingValue']
-        # sanity check
-        assert_greater_than_or_equal( shieldingValue ,  3.0 )
+        # sanity check. None of the expected values below will be correct if
+        # this is different
+        assert_equal( str(shieldingValue) ,  "3.00010000" )
 
         # TODO: this might not be enough time for slow machines, better
         # solution would be to wait until the opid finishes
@@ -140,19 +137,18 @@ class ShieldCoinbaseDonationTest (BitcoinTestFramework):
 
         rpc.z_listunspent()
 
-        # (300000000 - 1)*.95
-        # 284999999.05
-        # (300000000 - 1)*.05
-        # 14999999.95
+        # (300010000 - 1)*.05
+        # 15000499.95
+        # (300010000 - 1) - 15000499
+        # 285009500
         # The above value will be truncated (not rounded) by casting from
-        # double to CAmount/int64_t which means the donation will be 14999999
-        # and the sendAmount will be 300000000 - 1 (the fee) - 14999999 = 285000000
+        # double to CAmount/int64_t which means the donation will be 15000499
+        # and the sendAmount will be 300010000 - 1 (the fee) - 15000499 = 285009500
 
-        expectedSendAmount     = 285000000
-        expectedDonationAmount = 14999999
 
-        # actually seeing this: 2.84990500 + 0.14999500 = 2.99990000
-        # logging: donation=5, sendAmount=299999999, donationAmount=14999999
+        # these values assume that 3.0001 was shielded
+        expectedSendAmount     = 285009500
+        expectedDonationAmount = 15000499
 
         # lookup txid
         rawtx1 = rpc.z_viewtransaction(txid)