Remove repetitive assert_tx_failed

examples/stock/test_company.py

@@ -3,6 +3,7 @@
 from ethereum.tools import tester as t
 from ethereum import utils
 
+from tests.setup_transaction_tests import assert_tx_failed
 from viper import compiler
 
 @pytest.fixture
@@ -18,14 +19,7 @@ def tester():
             args=[tester.company_address, 1000, 10**6])
     return tester
 
-@pytest.fixture
-def assert_tx_failed(function_to_test, exception = t.TransactionFailed):
-    initial_state = tester.s.snapshot()
-    with pytest.raises(exception):
-        function_to_test()
-    tester.s.revert(initial_state)
-
-def test_overbuy(tester):
+def test_overbuy(tester, assert_tx_failed):
     # If all the stock has been bought, no one can buy more
     test_shares = int(tester.c.get_total_shares() / 2)
     test_value = int(test_shares * tester.c.get_price())
@@ -37,7 +31,7 @@ def test_overbuy(tester):
     assert_tx_failed(lambda: tester.c.buy_stock(sender=t.k1, value=one_stock))
     assert_tx_failed(lambda: tester.c.buy_stock(sender=t.k2, value=one_stock))
 
-def test_sell_without_stock(tester):
+def test_sell_without_stock(tester, assert_tx_failed):
     # If you don't have any stock, you can't sell
     assert_tx_failed(lambda: tester.c.sell_stock(1, sender=t.k1))
     assert_tx_failed(lambda: tester.c.sell_stock(1, sender=t.k2))
@@ -52,14 +46,14 @@ def test_sell_without_stock(tester):
     # But only until you run out
     assert_tx_failed(lambda: tester.c.sell_stock(1, sender=t.k1))
 
-def test_oversell(tester):
+def test_oversell(tester, assert_tx_failed):
     # You can't sell more than you own
     test_shares = int(tester.c.get_total_shares())
     test_value = int(test_shares * tester.c.get_price())
     tester.c.buy_stock(sender=t.k1, value=test_value)
     assert_tx_failed(lambda: tester.c.sell_stock(test_shares + 1, sender=t.k1))
 
-def test_transfer(tester):
+def test_transfer(tester, assert_tx_failed):
     # If you don't have any stock, you can't transfer
     assert_tx_failed(lambda: tester.c.transfer_stock(t.a2, 1, sender=t.k1))
     assert_tx_failed(lambda: tester.c.transfer_stock(t.a1, 1, sender=t.k2))
@@ -75,7 +69,7 @@ def test_transfer(tester):
     # But the other person does
     tester.c.sell_stock(test_shares, sender=t.k2)
 
-def test_paybill(tester):
+def test_paybill(tester, assert_tx_failed):
     # Only the company can authorize payments
     assert_tx_failed(lambda: tester.c.pay_bill(t.a2, 1, sender=t.k1))
     # A company can only pay someone if it has the money