diff --git a/src/main/python/ddadevops/infrastructure/release_mixin/infrastructure_api.py b/src/main/python/ddadevops/infrastructure/release_mixin/infrastructure_api.py
index 9ab5253..3b0a5d6 100644
--- a/src/main/python/ddadevops/infrastructure/release_mixin/infrastructure_api.py
+++ b/src/main/python/ddadevops/infrastructure/release_mixin/infrastructure_api.py
@@ -2,11 +2,15 @@ import json
 import re
 import subprocess as sub
 from abc import ABC, abstractmethod
+from typing import Optional, Union
 from pathlib import Path
 from os import environ
 
 # TODO: jem, zam - 2023_04_18: Discuss if we can move more functionality to domain?
 class FileHandler(ABC):
+    def __init__(self) -> None:
+        self.config_file_path: Optional[Path | None] = None
+        self.config_file_type: Optional[Path | None] = None
 
     @classmethod
     def from_file_path(cls, file_path):
@@ -40,6 +44,8 @@ class FileHandler(ABC):
 class JsonFileHandler(FileHandler):
 
     def parse(self) -> tuple[list[int], bool]:
+        if self.config_file_path is None:
+            raise ValueError("No file name given.")
         with open(self.config_file_path, 'r') as json_file:
             json_version = json.load(json_file)['version']
             is_snapshot = False
@@ -61,6 +67,8 @@ class JsonFileHandler(FileHandler):
 class GradleFileHandler(FileHandler):
 
     def parse(self) -> tuple[list[int], bool]:
+        if self.config_file_path is None:
+            raise ValueError("No file name given.")
         with open(self.config_file_path, 'r') as gradle_file:
             contents = gradle_file.read()
             version_line = re.search("\nversion = .*", contents)
@@ -68,19 +76,19 @@ class GradleFileHandler(FileHandler):
             if version_line is None:
                 raise exception
 
-            version_line = version_line.group()
+            version_line_group = version_line.group()
             version_string = re.search(
-                '[0-9]*\\.[0-9]*\\.[0-9]*(-SNAPSHOT)?', version_line)
+                '[0-9]*\\.[0-9]*\\.[0-9]*(-SNAPSHOT)?', version_line_group)
             if version_string is None:
                 raise exception
 
-            version_string = version_string.group()
+            version_string_group = version_string.group()
             is_snapshot = False
-            if '-SNAPSHOT' in version_string:
+            if '-SNAPSHOT' in version_string_group:
                 is_snapshot = True
-                version_string = version_string.replace('-SNAPSHOT', '')
+                version_string_group = version_string_group.replace('-SNAPSHOT', '')
 
-            version = [int(x) for x in version_string.split('.')]
+            version = [int(x) for x in version_string_group.split('.')]
 
             return version, is_snapshot
 
@@ -97,6 +105,8 @@ class GradleFileHandler(FileHandler):
 class PythonFileHandler(FileHandler):
 
     def parse(self) -> tuple[list[int], bool]:
+        if self.config_file_path is None:
+            raise ValueError("No file name given.")
         with open(self.config_file_path, 'r') as python_file:
             contents = python_file.read()
             version_line = re.search("\nversion = .*\n", contents)
@@ -104,19 +114,19 @@ class PythonFileHandler(FileHandler):
             if version_line is None:
                 raise exception
 
-            version_line = version_line.group()
+            version_line_group = version_line.group()
             version_string = re.search(
-                '[0-9]*\\.[0-9]*\\.[0-9]*(-SNAPSHOT)?', version_line)
+                '[0-9]*\\.[0-9]*\\.[0-9]*(-SNAPSHOT)?', version_line_group)
             if version_string is None:
                 raise exception
 
-            version_string = version_string.group()
+            version_string_group = version_string.group()
             is_snapshot = False
-            if '-SNAPSHOT' in version_string:
+            if '-SNAPSHOT' in version_string_group:
                 is_snapshot = True
-                version_string = version_string.replace('-SNAPSHOT', '')
+                version_string_group = version_string_group.replace('-SNAPSHOT', '')
 
-            version = [int(x) for x in version_string.split('.')]
+            version = [int(x) for x in version_string_group.split('.')]
 
             return version, is_snapshot
 
@@ -133,6 +143,8 @@ class PythonFileHandler(FileHandler):
 class ClojureFileHandler(FileHandler):
 
     def parse(self) -> tuple[list[int], bool]:
+        if self.config_file_path is None:
+            raise ValueError("No file name given.")
         with open(self.config_file_path, 'r') as clj_file:
             contents = clj_file.read()
             version_line = re.search("^\\(defproject .*\n", contents)
@@ -140,19 +152,19 @@ class ClojureFileHandler(FileHandler):
             if version_line is None:
                 raise exception
 
-            version_line = version_line.group()
+            version_line_group = version_line.group()
             version_string = re.search(
-                '[0-9]*\\.[0-9]*\\.[0-9]*(-SNAPSHOT)?', version_line)
+                '[0-9]*\\.[0-9]*\\.[0-9]*(-SNAPSHOT)?', version_line_group)
             if version_string is None:
                 raise exception
 
-            version_string = version_string.group()
+            version_string_group = version_string.group()
             is_snapshot = False
-            if '-SNAPSHOT' in version_string:
+            if '-SNAPSHOT' in version_string_group:
                 is_snapshot = True
-                version_string = version_string.replace('-SNAPSHOT', '')
+                version_string_group = version_string_group.replace('-SNAPSHOT', '')
 
-            version = [int(x) for x in version_string.split('.')]
+            version = [int(x) for x in version_string_group.split('.')]
 
             return version, is_snapshot
 
@@ -185,8 +197,14 @@ class SystemApi():
                            stderr=sub.PIPE,
                            text=True,
                            encoding="UTF-8")
-        self.stdout = stream.stdout.readlines()
-        self.stderr = stream.stderr.readlines()
+        if stream.stdout is not None: 
+            self.stdout = stream.stdout.readlines()
+        else:
+            self.stdout = None
+        if stream.stderr is not None: 
+            self.stderr = stream.stderr.readlines()
+        else:
+            self.stderr = None
 
     def run_checked(self, *args):
         self.run(args)