test coin minting and stake stabilizing

cryptarchia/test_ledger_state_update.py

@@ -176,17 +176,78 @@ class TestLedgerStateUpdate(TestCase):
         # coin wins the first slot
         block_1 = mk_block(slot=0, parent=genesis.block, coin=coin)
         follower.on_block(block_1)
-
         assert follower.tip_id() == block_1.id()
 
         # coin can't be reused to win following slots:
         block_2_reuse = mk_block(slot=1, parent=block_1.id(), coin=coin)
         follower.on_block(block_2_reuse)
-
         assert follower.tip_id() == block_1.id()
 
         # but the evolved coin is eligible
         block_2_evolve = mk_block(slot=1, parent=block_1.id(), coin=coin.evolve())
         follower.on_block(block_2_evolve)
-
         assert follower.tip_id() == block_2_evolve.id()
+
+    def test_new_coins_becoming_eligible_after_stake_distribution_stabilizes(self):
+        coin = Coin(sk=0, value=100)
+        genesis = mk_genesis_state([coin])
+
+        # An epoch will be 10 slots long, with stake distribution snapshot taken at the start of the epoch
+        # and nonce snapshot before slot 7
+        config = Config(
+            k=1,
+            active_slot_coeff=1,
+            epoch_stake_distribution_stabilization=4,
+            epoch_period_nonce_buffer=3,
+            epoch_period_nonce_stabilization=3,
+            time=TimeConfig(slot_duration=1, chain_start_time=0),
+        )
+
+        follower = Follower(genesis, config)
+
+        # ---- EPOCH 0 ----
+
+        block_0_0 = mk_block(slot=0, parent=genesis.block, coin=coin)
+        follower.on_block(block_0_0)
+        assert follower.tip() == block_0_0
+
+        # mint a new coin to be used for leader elections in upcoming epochs
+        coin_new = Coin(sk=1, value=10)
+        follower.ledger_state[block_0_0.id()].commitments_spend.add(
+            coin_new.commitment()
+        )
+
+        # the new coin is not yet eligible for elections
+
+        block_0_1_attempt = mk_block(slot=1, parent=block_0_0.id(), coin=coin_new)
+        follower.on_block(block_0_1_attempt)
+        assert follower.tip() == block_0_0
+
+        # whereas the evolved coin from genesis can be spent immediately
+
+        block_0_1 = mk_block(slot=1, parent=block_0_0.id(), coin=coin.evolve())
+        follower.on_block(block_0_1)
+        assert follower.tip() == block_0_1
+
+        # ---- EPOCH 1 ----
+
+        # The newly minted coin is still not eligible in the following epoch since the
+        # stake distribution snapshot is taken at the beginning of the previous epoch
+
+        block_1_0 = mk_block(slot=10, parent=block_0_1.id(), coin=coin_new)
+        follower.on_block(block_1_0)
+        assert follower.tip() == block_0_1
+
+        # ---- EPOCH 2 ----
+
+        # The coin is finally eligible 2 epochs after it was first minted
+
+        block_2_0 = mk_block(slot=20, parent=block_0_1.id(), coin=coin_new)
+        follower.on_block(block_2_0)
+        assert follower.tip() == block_2_0
+
+        # And now the minted coin can freely use the evolved coin for subsequent blocks
+
+        block_2_1 = mk_block(slot=20, parent=block_2_0.id(), coin=coin_new.evolve())
+        follower.on_block(block_2_1)
+        assert follower.tip() == block_2_1