Merge pull request #192 from carver/constant-block-gas

Make gas limit constant
ethereum · Jun 1, 2020 · 171dce6 · 171dce6
2 parents e7a3fbf + c140e63
commit 171dce6
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diff --git a/CHANGELOG b/CHANGELOG
@@ -1,10 +1,18 @@
 Unreleased
 -------------
 
+- Breaking changes
+
+  - Make gas limit constant for py-evm backend
+    https://github.com/ethereum/eth-tester/pull/192
+
 - Features
 
   - Add support for gas estimate block identifiers
+    https://github.com/ethereum/eth-tester/pull/189
   - Add support for custom virtual machine fork schedule in PyEVMBackend
+    https://github.com/ethereum/eth-tester/pull/191
+
 
 v0.4.0-beta.2
 -------------

diff --git a/eth_tester/backends/pyevm/main.py b/eth_tester/backends/pyevm/main.py
@@ -164,7 +164,15 @@ def setup_tester_chain(
         consensus_applier = ConsensusApplier(NoProofConsensus)
         no_proof_vms = consensus_applier.amend_vm_configuration(vm_configuration)
 
-    MainnetTesterNoProofChain = MiningChain.configure(vm_configuration=no_proof_vms)
+    class MainnetTesterNoProofChain(MiningChain):
+        vm_configuration = no_proof_vms
+
+        def create_header_from_parent(self, parent_header, **header_params):
+            # Keep the gas limit constant
+            return super().create_header_from_parent(
+                parent_header,
+                **assoc(header_params, 'gas_limit', parent_header.gas_limit)
+            )
 
     if genesis_params is None:
         genesis_params = get_default_genesis_params()

diff --git a/eth_tester/utils/backend_testing.py b/eth_tester/utils/backend_testing.py
@@ -244,6 +244,13 @@ def test_mine_multiple_blocks(self, eth_tester):
         assert is_integer(after_block_number)
         assert before_block_number == after_block_number - 10
 
+    def test_gas_limit_constant(self, eth_tester):
+        eth_tester.mine_blocks()
+        before_gas_limit = eth_tester.get_block_by_number('latest')['gas_limit']
+        eth_tester.mine_blocks()
+        after_gas_limit = eth_tester.get_block_by_number('latest')['gas_limit']
+        assert before_gas_limit == after_gas_limit
+
     #
     # Transaction Sending
     #

diff --git a/tests/backends/test_pyevm.py b/tests/backends/test_pyevm.py
@@ -146,7 +146,7 @@ def test_override_genesis_parameters(self):
 
         # Establish a custom gas limit
         param_overrides = {"gas_limit": 4750000}
-        block_one_gas_limit = 4745362
+        block_one_gas_limit = param_overrides['gas_limit']
 
         # Initialize PyEVM backend with custom genesis parameters
         genesis_params = PyEVMBackend._generate_genesis_params(