Merge #14964: test: Fix race in mempool_accept

faee591 test: Fix race in mempool_accept (MarcoFalke)

Pull request description:

  If we happen to pick the same random coin to spend, there would be mempool conflicts in some runs of the test. Fix that by popping from a static list of coins to spend from.

Tree-SHA512: f6fd37e43d919371aa8bc3a2c93b569f9169961fe702f3641bb63180c3a88f12ca1857e9ed4d3723d5f04ca8ab5ef009a90e679580f36246a10b987620a55bee

Author: MarcoFalke

test/functional/mempool_accept.py

@@ -58,14 +58,15 @@ def run_test(self):
         self.mempool_size = 0
         wait_until(lambda: node.getblockcount() == 200)
         assert_equal(node.getmempoolinfo()['size'], self.mempool_size)
+        coins = node.listunspent()
 
         self.log.info('Should not accept garbage to testmempoolaccept')
         assert_raises_rpc_error(-3, 'Expected type array, got string', lambda: node.testmempoolaccept(rawtxs='ff00baar'))
         assert_raises_rpc_error(-8, 'Array must contain exactly one raw transaction for now', lambda: node.testmempoolaccept(rawtxs=['ff00baar', 'ff22']))
         assert_raises_rpc_error(-22, 'TX decode failed', lambda: node.testmempoolaccept(rawtxs=['ff00baar']))
 
         self.log.info('A transaction already in the blockchain')
-        coin = node.listunspent()[0]  # Pick a random coin(base) to spend
+        coin = coins.pop()  # Pick a random coin(base) to spend
         raw_tx_in_block = node.signrawtransactionwithwallet(node.createrawtransaction(
             inputs=[{'txid': coin['txid'], 'vout': coin['vout']}],
             outputs=[{node.getnewaddress(): 0.3}, {node.getnewaddress(): 49}],
@@ -93,7 +94,7 @@ def run_test(self):
         )
 
         self.log.info('A final transaction not in the mempool')
-        coin = node.listunspent()[0]  # Pick a random coin(base) to spend
+        coin = coins.pop()  # Pick a random coin(base) to spend
         raw_tx_final = node.signrawtransactionwithwallet(node.createrawtransaction(
             inputs=[{'txid': coin['txid'], 'vout': coin['vout'], "sequence": 0xffffffff}],  # SEQUENCE_FINAL
             outputs=[{node.getnewaddress(): 0.025}],