support gas estimates with block identifier

CHANGELOG

@@ -1,7 +1,9 @@
 Unreleased
 -------------
 
-None
+- Features
+
+	- Add support for gas estimate block identifiers
 
 v0.4.0-beta.2
 -------------

eth_tester/backends/base.py

@@ -91,7 +91,7 @@ def send_signed_transaction(self, transaction):
         raise NotImplementedError("Must be implemented by subclasses")
 
     @abstractmethod
-    def estimate_gas(self, transaction):
+    def estimate_gas(self, transaction, block_number="latest"):
         raise NotImplementedError("Must be implemented by subclasses")
 
     @abstractmethod

eth_tester/backends/pyevm/main.py

@@ -465,12 +465,26 @@ def _max_available_gas(self):
     @replace_exceptions({
         EVMInvalidInstruction: TransactionFailed,
         EVMRevert: TransactionFailed})
-    def estimate_gas(self, transaction):
-        evm_transaction = self._get_normalized_and_unsigned_evm_transaction(assoc(
-            transaction, 'gas', 21000))
+    def estimate_gas(self, transaction, block_number="latest"):
+        evm_transaction = self._get_normalized_and_unsigned_evm_transaction(
+            assoc(transaction, 'gas', 21000),
+            block_number
+        )
         spoofed_transaction = EVMSpoofTransaction(evm_transaction, from_=transaction['from'])
 
-        return self.chain.estimate_gas(spoofed_transaction)
+        if block_number == "latest":
+            return self.chain.estimate_gas(spoofed_transaction)
+        elif block_number == "earliest":
+            return self.chain.estimate_gas(
+                spoofed_transaction, self.chain.get_canonical_block_header_by_number(0)
+            )
+        elif block_number == "pending":
+            raise NotImplementedError('"pending" block identifier is unsupported in eth-tester')
+        else:
+            return self.chain.estimate_gas(
+                spoofed_transaction,
+                self.chain.get_canonical_block_header_by_number(block_number),
+            )
 
     def is_eip838_error(self, error):
         if not isinstance(error, EVMRevert):

eth_tester/main.py

@@ -428,10 +428,12 @@ def call(self, transaction, block_number="latest"):
         result = self.normalizer.normalize_outbound_return_data(raw_result)
         return result
 
-    def estimate_gas(self, transaction):
+    def estimate_gas(self, transaction, block_number="latest"):
         self.validator.validate_inbound_transaction(transaction, txn_type='estimate')
         raw_transaction = self.normalizer.normalize_inbound_transaction(transaction)
-        raw_gas_estimate = self.backend.estimate_gas(raw_transaction)
+        self.validator.validate_inbound_block_number(block_number)
+        raw_block_number = self.normalizer.normalize_inbound_block_number(block_number)
+        raw_gas_estimate = self.backend.estimate_gas(raw_transaction, raw_block_number)
         self.validator.validate_outbound_gas_estimate(raw_gas_estimate)
         gas_estimate = self.normalizer.normalize_outbound_gas_estimate(raw_gas_estimate)
         return gas_estimate

eth_tester/utils/backend_testing.py

@@ -686,6 +686,21 @@ def test_estimate_gas(self, eth_tester):
         # https://github.com/ethereum/py-evm/blob/f0276e684edebd7cd9e84cd04b3229ab9dd958b9/evm/estimators/__init__.py#L11
         assert receipt['gas_used'] >= gas_estimation - 21000
 
+    def test_estimate_gas_with_block_identifier(self, eth_tester):
+        self.skip_if_no_evm_execution()
+
+        math_address = _deploy_math(eth_tester)
+        estimate_call_math_transaction = _make_call_math_transaction(
+            eth_tester, math_address, "increment",
+        )
+        latest_gas_estimation = eth_tester.estimate_gas(
+            estimate_call_math_transaction, "latest"
+        )
+        earliest_gas_estimation = eth_tester.estimate_gas(
+            estimate_call_math_transaction, "earliest"
+        )
+        assert latest_gas_estimation != earliest_gas_estimation
+
     def test_can_call_after_exception_raised_calling(self, eth_tester):
         self.skip_if_no_evm_execution()