feat: test coverage more than 85%

internal/io/writer.go

@@ -11,7 +11,13 @@ type writer struct {
 	dirPath string
 }
 
+// WriteFile writes file into `w writer` directory.
+// Returns outputPath and error
 func (w writer) WriteFile(filename string, data []byte) (string, error) {
+	if filename == "" {
+		return "", fmt.Errorf("filename cannot be empty")
+	}
+
 	if w.dirPath == "" {
 		return "", fmt.Errorf("export directory cannot be empty")
 	}
@@ -27,6 +33,10 @@ func (w writer) WriteFile(filename string, data []byte) (string, error) {
 }
 
 func NewWriter(dirPath string) io.WriterIface {
+	return newWriter(dirPath)
+}
+
+func newWriter(dirPath string) *writer {
 	return &writer{
 		dirPath: dirPath,
 	}