fix/reinit (#8)

* test: reinit bug

* fix: reinit bug

contracts/VestingEscrowFactory.vy

@@ -1,4 +1,4 @@
-# @version 0.2.8
+# @version 0.2.16
 """
 @title Vesting Escrow Factory
 @author Curve Finance, Yearn Finance

contracts/VestingEscrowSimple.vy

@@ -1,4 +1,4 @@
-# @version 0.2.8
+# @version 0.2.16
 """
 @title Simple Vesting Escrow
 @author Curve Finance, Yearn Finance
@@ -35,14 +35,15 @@ cliff_length: public(uint256)
 total_locked: public(uint256)
 total_claimed: public(uint256)
 disabled_at: public(uint256)
+initialized: public(bool)
 
 admin: public(address)
 future_admin: public(address)
 
 @external
 def __init__():
     # ensure that the original contract cannot be initialized
-    self.admin = msg.sender
+    self.initialized = True
 
 
 @external
@@ -69,7 +70,8 @@ def initialize(
     @param end_time Time until everything should be vested
     @param cliff_length Duration after which the first portion vests
     """
-    assert self.admin == ZERO_ADDRESS  # dev: can only initialize once
+    assert not self.initialized  # dev: can only initialize once
+    self.initialized = True
 
     self.token = ERC20(token)
     self.admin = admin

contracts/test/ERC20.vy

@@ -2,7 +2,7 @@
 @notice Mock ERC20 for testing
 """
 
-# @version 0.2.8
+# @version 0.2.16
 
 event Transfer:
     _from: indexed(address)

tests/functional/VestingEscrow/test_init.py

@@ -0,0 +1,9 @@
+import brownie
+
+
+def test_reinit_impossible(vesting, accounts, token):
+    vesting.renounce_ownership({"from": accounts[0]})
+    with brownie.reverts("dev: can only initialize once"):
+        vesting.initialize(
+            accounts[1], token, accounts[1], 0, 0, 0, 0, {"from": accounts[1]}
+        )