diff --git a/hatch.py b/hatch.py
index fd6ec0b..384ed8a 100644
--- a/hatch.py
+++ b/hatch.py
@@ -26,13 +26,14 @@ def hatch_raise_split_pools(total_hatch_raise, hatch_tribute) -> Tuple[float, fl
     collateral_pool = total_hatch_raise * (1-hatch_tribute)
     return funding_pool, collateral_pool
 
-def contributions_to_token_batches(hatcher_contributions: List[int], initial_token_supply: int, vesting_80p_unlocked: int) -> List[float]:
+def contributions_to_token_batches(hatcher_contributions: List[int], desired_token_price: float, vesting_80p_unlocked: int) -> Tuple[List[float], float]:
     """
-    hatcher_contributions: a list of hatcher contributions
-    initial_token_supply: NOT denominated in millions
+    hatcher_contributions: a list of hatcher contributions in DAI/ETH/whatever
+    desired_token_price: used to determine the initial token supply
     vesting_80p_unlocked: vesting parameter - the number of days after which 80% of tokens will be unlocked, including the cliff period
     """
     total_hatch_raise = sum(hatcher_contributions)
+    initial_token_supply = total_hatch_raise / desired_token_price
 
     # In the hatch, everyone buys in at the same time, with the same price. So just split the token supply amongst the hatchers proportionally to their contributions
     tokens_per_hatcher = [(x / total_hatch_raise) * initial_token_supply for x in hatcher_contributions]
@@ -40,7 +41,7 @@ def contributions_to_token_batches(hatcher_contributions: List[int], initial_tok
     cliff_days, halflife_days = convert_80p_to_cliff_and_halflife(vesting_80p_unlocked)
 
     token_batches = [TokenBatch(x, cliff_days, halflife_days, hatch=True) for x in tokens_per_hatcher]
-    return token_batches
+    return token_batches, initial_token_supply
 
 class TokenBatch:
     def __init__(self, value: float, cliff_days: int, halflife_days: int, hatch = False):
@@ -51,16 +52,18 @@ class TokenBatch:
         self.halflife_days = halflife_days
         self.spent = 0
 
+        self.current_date = datetime.today()  # to be set externally before each spend check
+
     def __repr__(self):
-        o = "TokenBatch {} {}, Unlocked: {}".format("Hatch" if self.hatch_tokens else "", self.value, self.unlocked_fraction(datetime.today()))
+        o = "TokenBatch {} {}, Unlocked: {}".format("Hatch" if self.hatch_tokens else "", self.value, self.unlocked_fraction())
         return o
 
-    def unlocked_fraction(self, day: datetime = datetime.today()) -> float:
+    def unlocked_fraction(self) -> float:
         """
         returns what fraction of the TokenBatch is unlocked to date
         """
         if self.hatch_tokens:
-            days_delta = day - self.creation_date
+            days_delta = self.current_date - self.creation_date
             u = vesting_curve(days_delta.days, self.cliff_days, self.halflife_days)
             return u if u > 0 else 0
         else:
@@ -72,7 +75,7 @@ class TokenBatch:
         returns the argument if successful for your convenience
         """
         if x > self.spendable():
-            raise Exception("Not so many tokens are available for you to spend yet!")
+            raise Exception("Not so many tokens are available for you to spend yet ({})".format(self.current_date))
 
         self.value -= x
         self.spent += x
@@ -98,7 +101,7 @@ class Commons:
 
         # Options
         self.exit_tribute = exit_tribute
-    
+
     def deposit(self, dai):
         """
         Deposit DAI after the hatch phase. This means all the incoming deposit goes to the collateral pool.
@@ -118,8 +121,8 @@ class Commons:
         money_returned = dai
 
         if self.exit_tribute:
-            self._funding_pool += commons.exit_tribute * dai
-            money_returned = (1-commons.exit_tribute) * dai 
+            self._funding_pool += self.exit_tribute * dai
+            money_returned = (1-self.exit_tribute) * dai
 
         return money_returned, realized_price
     
diff --git a/hatch_test.py b/hatch_test.py
index 944d173..a173b28 100644
--- a/hatch_test.py
+++ b/hatch_test.py
@@ -2,7 +2,7 @@ from hatch import *
 import unittest
 import datetime
 
-class TestHatch(unittest.TestCase):
+class HatchTest(unittest.TestCase):
     def test_vesting_curve(self):
         self.assertEqual(vesting_curve(90, 90, 90), 0)  # At Day 90, the cliff has just ended and the vesting curve has begun at 0
         self.assertEqual(vesting_curve(180, 90, 90), 0.5)  # At Day 180, the cliff has ended and we are in the vesting curve, whose half-life is 90 as well, so at 180 we should get 0.5.
@@ -16,9 +16,11 @@ class TokenBatchTest(unittest.TestCase):
         tbh = TokenBatch(10000, 3, 3, True)
         tb = TokenBatch(10000, 5, 10, False)
 
+        self. assertEqual(tbh.unlocked_fraction(), 0)
+        tbh.current_date = datetime.datetime.today() + datetime.timedelta(days=3)
         self.assertEqual(tbh.unlocked_fraction(), 0)
-        self.assertEqual(tbh.unlocked_fraction(datetime.datetime.today() + datetime.timedelta(days=3)), 0)
-        self.assertEqual(tbh.unlocked_fraction(datetime.datetime.today() + datetime.timedelta(days=6)), 0.5)
+        tbh.current_date = datetime.datetime.today() + datetime.timedelta(days=6)
+        self.assertEqual(tbh.unlocked_fraction(), 0.5)
 
         self.assertEqual(tb.unlocked_fraction(), 1.0)
     
@@ -39,22 +41,30 @@ class TokenBatchTest(unittest.TestCase):
         with self.assertRaises(Exception):
             tb.spend(10000)
 
-class TestSystem(unittest.TestCase):
-    def test_system(self):
+class CommonsTest(unittest.TestCase):
+    def setUp(self):
         # 100,000 DAI invested for 1,000,000 tokens.
-        desired_token_price = 0.1
-        hatcher_contributions = [25000, 25000, 50000]
-        token_supply_initial = sum(hatcher_contributions) / desired_token_price
-        token_batches = contributions_to_token_batches(hatcher_contributions, token_supply_initial, 90)
+        self.desired_token_price = 0.1
+        self.hatcher_contributions = [25000, 25000, 50000]
+        self.token_batches, self.token_supply_initial = contributions_to_token_batches(self.hatcher_contributions, self.desired_token_price, 90)
 
         # Because of hatch_tribute, the collateral_pool is 0.7e6. This causes the token's post-hatch price to be 0.14.
-        o = Commons(sum(hatcher_contributions), token_supply_initial, hatch_tribute=0.3)
-        self.assertEqual(o._collateral_pool, 70000)
-        self.assertEqual(o._funding_pool, 30000)
-        self.assertEqual(o._token_supply, token_supply_initial)
+        self.commons = Commons(sum(self.hatcher_contributions), self.token_supply_initial, hatch_tribute=0.3)
 
-        self.assertEqual(o.token_price(), 0.14)
-        print(token_batches)
-        # print(o.deposit(100))
-        # print(o.token_price())
-        # print(o._collateral_pool)
\ No newline at end of file
+    def test_initialization(self):
+        self.assertEqual(self.commons._collateral_pool, 70000)
+        self.assertEqual(self.commons._funding_pool, 30000)
+        self.assertEqual(self.commons._token_supply, self.token_supply_initial)
+
+        self.assertEqual(self.commons.token_price(), 0.14)
+
+    def test_burn_without_exit_tribute(self):
+        old_token_supply = self.commons._token_supply
+        old_collateral_pool = self.commons._collateral_pool
+
+        money_returned, realized_price = self.commons.burn(50000)
+
+        self.assertEqual(money_returned, 6825.0)
+        self.assertEqual(realized_price, 0.1365)
+        self.assertEqual(self.commons._token_supply, old_token_supply-50000)
+        self.assertEqual(self.commons._collateral_pool, old_collateral_pool-money_returned)
\ No newline at end of file