diff --git a/athena_abi/core.go b/athena_abi/core.go
index 621c7b1e..3151afca 100644
--- a/athena_abi/core.go
+++ b/athena_abi/core.go
@@ -5,11 +5,9 @@ import (
 	"log"
 )
 
-type b256 [32]byte
-
 type StarknetABI struct {
 	ABIName               *string
-	ClassHash             b256
+	ClassHash             []byte
 	Functions             map[string]AbiFunction
 	Events                map[string]AbiEvent
 	Constructor           []AbiParameter
@@ -17,45 +15,47 @@ type StarknetABI struct {
 	ImplementedInterfaces map[string]AbiInterface
 }
 
+// Declare errors
+var (
+	errParseDefinedTypes          = errors.New("unable to parse defined types")
+	errParseInterfaces            = errors.New("unable to parse interfaces")
+	errParseFunctions             = errors.New("unable to parse functions")
+	errParseEvents                = errors.New("unable to parse events")
+	errParseConstructor           = errors.New("unable to parse constructor")
+	errParseL1Handler             = errors.New("unable to parse L1 handler")
+	errParseImplementedInterfaces = errors.New("unable to parse implemented interfaces")
+)
+
 // Parse Starknet ABI from JSON
 // @param abiJSON
 // @param abiname
 // @param classHash
-func StarknetAbiFromJSON(abiJson []map[string]interface{}, abiName string, classHash b256) (*StarknetABI, error) {
-	if abiJson == nil {
-		return nil, errors.New("unable to parse ABI")
-	}
+func StarknetAbiFromJSON(abiJson []map[string]interface{}, abiName string, classHash []byte) (*StarknetABI, error) {
 	groupedAbi := GroupAbiByType(abiJson)
 
 	// Parse defined types (structs and enums)
-	if groupedAbi["type_def"] == nil {
-		log.Println("No type definitions found in ABI")
-	}
 	definedTypes, err := ParseEnumsAndStructs(groupedAbi["type_def"])
 	if err != nil {
 		sortedDefs, errDef := TopoSortTypeDefs(groupedAbi["type_def"])
-		if errDef != nil {
-			return nil, errors.New("unable to parse types")
+		if errDef == nil {
+			defineTypes, errDtypes := ParseEnumsAndStructs(sortedDefs)
+			definedTypes = defineTypes
+			errDef = errDtypes
 		}
-		defineTypes, errDtypes := ParseEnumsAndStructs(sortedDefs)
-		definedTypes = defineTypes
-		if errDtypes != nil {
-			return nil, errors.New("unable to parse types")
+		if errDef != nil {
+			return nil, errParseDefinedTypes
 		}
 		log.Println("ABI Struct and Enum definitions out of order & required topological sorting")
 	}
 
 	// Parse interfaces
 	var definedInterfaces []AbiInterface
-	if groupedAbi["interface"] == nil {
-		log.Println("No interfaces found in ABI")
-	}
 	for _, iface := range groupedAbi["interface"] {
 		functions := []AbiFunction{}
 		for _, funcData := range iface["items"].([]interface{}) {
 			parsedAbi, errWhileParsing := ParseAbiFunction(funcData.(map[string]interface{}), definedTypes)
 			if errWhileParsing != nil {
-				return nil, errors.New("unable to parse interfaces")
+				return nil, errParseInterfaces
 			}
 			functions = append(functions, *parsedAbi)
 		}
@@ -66,21 +66,17 @@ func StarknetAbiFromJSON(abiJson []map[string]interface{}, abiName string, class
 	}
 
 	// Parse functions
-	if groupedAbi["function"] == nil {
-		log.Println("No functions found in ABI")
-	}
 	functions := make(map[string]AbiFunction)
 	for _, functionData := range groupedAbi["function"] {
 		funcName := functionData["name"].(string)
 		abiFunc, errParsingFunctions := ParseAbiFunction(functionData, definedTypes)
 		if errParsingFunctions != nil {
-			return nil, errors.New("unable to parse functions")
+			return nil, errParseFunctions
 		}
 		functions[funcName] = *abiFunc
 	}
 
 	// Add functions from interfaces
-
 	for _, iface := range definedInterfaces {
 		for _, function := range iface.functions {
 			functions[function.name] = function
@@ -89,19 +85,14 @@ func StarknetAbiFromJSON(abiJson []map[string]interface{}, abiName string, class
 
 	// Parse events
 	parsedAbiEvents := []AbiEvent{}
-	if groupedAbi["event"] == nil {
-		log.Println("No events found in ABI")
-	}
 	for _, eventData := range groupedAbi["event"] {
 		parsedEvent, errParsingEvent := ParseAbiEvent(eventData, definedTypes)
 		if errParsingEvent != nil {
-			return nil, errors.New("unable to parse events")
+			return nil, errParseEvents
 		}
 		parsedAbiEvents = append(parsedAbiEvents, *parsedEvent)
 	}
-	if len(parsedAbiEvents) == 0 {
-		log.Println("No events found in ABI")
-	}
+
 	events := make(map[string]AbiEvent)
 	for _, event := range parsedAbiEvents {
 		if event.name != "" {
@@ -116,7 +107,7 @@ func StarknetAbiFromJSON(abiJson []map[string]interface{}, abiName string, class
 			param := paramData.(map[string]interface{})
 			typed, errorParsingType := parseType(param["type"].(string), definedTypes)
 			if errorParsingType != nil {
-				return nil, errors.New("unable to parse constructor")
+				return nil, errParseConstructor
 			}
 			constructor = append(constructor, AbiParameter{
 				Name: param["name"].(string),
@@ -132,7 +123,7 @@ func StarknetAbiFromJSON(abiJson []map[string]interface{}, abiName string, class
 	if len(groupedAbi["l1_handler"]) == 1 {
 		handler, errorParsingFunction := ParseAbiFunction(groupedAbi["l1_handler"][0], definedTypes)
 		if errorParsingFunction != nil {
-			return nil, errors.New("unable to parse L1 handler")
+			return nil, errParseL1Handler
 		}
 		l1Handler = handler
 	} else {
@@ -143,7 +134,7 @@ func StarknetAbiFromJSON(abiJson []map[string]interface{}, abiName string, class
 	implementedInterfaces := make(map[string]AbiInterface)
 	implArray, ok := groupedAbi["impl"]
 	if !ok {
-		return nil, errors.New("unable to parse implemented interfaces")
+		return nil, errParseImplementedInterfaces
 	}
 	for _, implData := range implArray {
 		implMap := implData