Add tests

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Fixed
+- [#227](https://github.com/deviceinsight/kafkactl/issues/227) Incorrect handling of Base64-encoded values when producing from JSON
 
 ## 5.4.0 - 2024-11-28
 ### Added

internal/producer/MessageSerializer_test.go

@@ -0,0 +1,65 @@
+package producer
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestDecodeBytesBase64WhenInputIsNil(t *testing.T) {
+	got, err := decodeBytes(nil, "base64")
+	if got != nil {
+		t.Errorf("Expected nil, got %v", got)
+	}
+	if err != nil {
+		t.Errorf("Expected nil, got %v", err)
+	}
+}
+
+func TestDecodeBytesBase64WhenInputIsInvalid(t *testing.T) {
+	got, err := decodeBytes([]byte("..this..is..not..base64.."), "base64")
+	if got != nil {
+		t.Errorf("Expected nil, got %v", got)
+	}
+	if err == nil {
+		t.Errorf("Expected error, got nil")
+	}
+}
+
+func TestDecodeBytesBase64WithRegularInput(t *testing.T) {
+	// length 4
+	got, err := decodeBytes([]byte("dGVzdA=="), "base64")
+	if string(got) != "test" {
+		t.Errorf("Expected hello, got %v", string(got))
+	}
+	if err != nil {
+		t.Errorf("Expected nil, got %v", err)
+	}
+	// length 5
+	got, err = decodeBytes([]byte("aGVsbG8="), "base64")
+	if string(got) != "hello" {
+		t.Errorf("Expected hello, got %v", string(got))
+	}
+	if err != nil {
+		t.Errorf("Expected nil, got %v", err)
+	}
+
+	// length 6
+	got, err = decodeBytes([]byte("aGVsbG8h"), "base64")
+	if string(got) != "hello!" {
+		t.Errorf("Expected hello, got %v", string(got))
+	}
+	if err != nil {
+		t.Errorf("Expected nil, got %v", err)
+	}
+}
+
+func TestDecodeBytesBase64WithZeroPaddedInput(t *testing.T) {
+	got, err := decodeBytes([]byte("AAAAAAAD"), "base64")
+	expected := []byte{0, 0, 0, 0, 0, 3}
+	if !reflect.DeepEqual(got, expected) {
+		t.Errorf("Expected hello, got %v", got)
+	}
+	if err != nil {
+		t.Errorf("Expected nil, got %v", err)
+	}
+}