Fix read-only write protection check and enhance precompiled contract tests

Author: Frozen

core/vm/contracts.go

@@ -293,7 +293,7 @@ func RunPrecompiledContract(p WriteCapablePrecompiledContract, evm *EVM, contrac
 		//return RunPrecompiledContract(p, evm, input, contract, readOnly)
 	}
 	// immediately error out if readOnly
-	if readOnly && !p.IsWrite() {
+	if readOnly && p.IsWrite() {
 		return nil, 0, errWriteProtection
 	}
 	gasCost, err := p.RequiredGas(evm, contract, input)

core/vm/contracts_write_test.go

@@ -210,9 +210,12 @@ func TestStakingPrecompiles(t *testing.T) {
 }
 
 func TestWriteCapablePrecompilesReadOnly(t *testing.T) {
-	p := &stakingPrecompile{}
-	expectedError := errWriteProtection
-	res, _, err := RunPrecompiledContract(p, nil, nil, []byte{}, 0, true)
+	var (
+		p             = &stakingPrecompile{}
+		expectedError = errWriteProtection
+		env           = NewEVM(BlockContext{ShardID: 1}, TxContext{}, nil, params.TestChainConfig, Config{})
+		res, _, err   = RunPrecompiledContract(p, env, nil, []byte{}, 0, true)
+	)
 	if err != nil {
 		if err.Error() != expectedError.Error() {
 			t.Errorf("Expected error %v, got %v", expectedError, err)

core/vm/evm_test.go

@@ -20,16 +20,12 @@ func TestEpochPrecompile(t *testing.T) {
 		CodeAddr: &precompileAddr,
 		Gas:      GasQuickStep,
 	}
-	result, err := run(evm,
-		&contract,
-		input,
-		true,
-	)
+	result, _, err := RunPrecompiledContract(&epoch{}, evm, &contract, input, GasQuickStep, true)
 	if err != nil {
 		t.Fatalf("Got error%v\n", err)
 	}
 	resultingEpoch := new(big.Int).SetBytes(result)
 	if resultingEpoch.Cmp(targetEpoch) != 0 {
-		t.Error("Epoch did not match")
+		t.Errorf("Epoch did not match, expected %d, got %d", targetEpoch.Int64(), resultingEpoch.Int64())
 	}
 }