fix(tests): EIP-7883 minor fixes

tests/osaka/eip7883_modexp_gas_increase/conftest.py

@@ -60,14 +60,19 @@ def total_tx_gas_needed(
         fork.transaction_intrinsic_cost_calculator()
     )
     memory_expansion_gas_calculator = fork.memory_expansion_gas_calculator()
-    sstore_gas = fork.gas_costs().G_STORAGE_SET * (len(modexp_expected) // 32)
+    # `gas_measure_contract` does at most 4 SSTOREs to cold slots.
+    sstore_gas = (
+        fork.gas_costs().G_STORAGE_SET + fork.gas_costs().G_COLD_SLOAD
+    ) * 4
+    # Ensures that the precompile call is not starved by the 63/64 rule.
+    precompile_gas_with_margin = precompile_gas * 64 // 63
     extra_gas = 100_000
 
     return (
         extra_gas
         + intrinsic_gas_cost_calculator(calldata=bytes(modexp_input))
         + memory_expansion_gas_calculator(new_bytes=len(bytes(modexp_input)))
-        + precompile_gas
+        + precompile_gas_with_margin
         + sstore_gas
     )
 
@@ -219,11 +224,11 @@ def precompile_gas(
     Calculate gas cost for the ModExp precompile and verify it matches expected
     gas.
     """
-    spec = Spec if fork < Osaka else Spec7883
+    spec = Spec7883 if fork >= Osaka else Spec
     try:
         calculated_gas = spec.calculate_gas_cost(modexp_input)
         if gas_old is not None and gas_new is not None:
-            expected_gas = gas_old if fork < Osaka else gas_new
+            expected_gas = gas_new if fork >= Osaka else gas_old
             base_len = len(modexp_input.base)
             exp_len = len(modexp_input.exponent)
             mod_len = len(modexp_input.modulus)