diff --git a/app/ptxboa_functions.py b/app/ptxboa_functions.py
index 31e5989d..8184292a 100644
--- a/app/ptxboa_functions.py
+++ b/app/ptxboa_functions.py
@@ -7,13 +7,14 @@
 import streamlit as st
 
 from ptxboa.api import PtxboaAPI
+from ptxboa.utils import is_test
 
 
 def calculate_results_single(
     _api: PtxboaAPI,
     settings: dict,
     user_data: pd.DataFrame | None = None,
-    optimize_flh: bool = False,
+    optimize_flh: bool = True,
 ) -> pd.DataFrame:
     """Calculate results for a single set of settings.
 
@@ -88,6 +89,10 @@ def calculate_results_list(
     # copy settings from session_state:
     settings = {key: st.session_state[key] for key in setting_keys}
 
+    # in test environment: do not optimize by default
+    # NOTE: does not work in global, must be called here in a function
+    optimize_flh = not is_test()
+
     # update settings from session state with custom values
     if override_session_state is not None:
         if not set(override_session_state.keys()).issubset(set(setting_keys)):
@@ -109,10 +114,7 @@ def calculate_results_list(
     for parameter in parameter_list:
         settings.update({parameter_to_change: parameter})
         # only optimize when using actual chosen parameter set:
-        if st.session_state[parameter_to_change] == parameter:
-            optimize_flh = True
-        else:
-            optimize_flh = False
+
         res_single = calculate_results_single(
             api,
             settings,
diff --git a/ptxboa/__init__.py b/ptxboa/__init__.py
index dd395f09..4c1419a6 100644
--- a/ptxboa/__init__.py
+++ b/ptxboa/__init__.py
@@ -2,20 +2,13 @@
 """Common Paths and settings."""
 import logging
 import os
-import warnings
 from pathlib import Path
 
-# disable warnings for loading networks
-
-warnings.filterwarnings("ignore", category=DeprecationWarning)
-
-
-IS_TEST = "PYTEST_CURRENT_TEST" in os.environ  # TODO unused
 KEY_SEPARATOR = ","
 
+
 # PATHS
 _THIS_DIR = Path(__file__).parent.resolve()
-
 PROFILES_DIR = _THIS_DIR / ".." / "flh_opt" / "renewable_profiles"
 STATIC_DATA_DIR = _THIS_DIR / "static"
 DEFAULT_CACHE_DIR = Path(os.environ.get("PTXBOA_CACHE_DIR") or _THIS_DIR / "cache")
diff --git a/ptxboa/api.py b/ptxboa/api.py
index ce32cfaf..058c2f7e 100644
--- a/ptxboa/api.py
+++ b/ptxboa/api.py
@@ -121,7 +121,7 @@ def calculate(
         ship_own_fuel: bool,
         output_unit: OutputUnitType = "USD/MWh",
         user_data: pd.DataFrame | None = None,
-        optimize_flh: bool = False,
+        optimize_flh: bool = True,
     ) -> Tuple[pd.DataFrame, object]:
         """Calculate results based on user selection.
 
diff --git a/ptxboa/utils.py b/ptxboa/utils.py
index 6e47e9a3..c9975137 100644
--- a/ptxboa/utils.py
+++ b/ptxboa/utils.py
@@ -1,6 +1,8 @@
 # -*- coding: utf-8 -*-
 """Utilities."""
 
+import os
+
 
 def annuity(rate: float, periods: int, value: float) -> float:
     """Calculate annuity.
@@ -38,3 +40,10 @@ def __call__(cls, *args):
         if key not in cls._instances:
             cls._instances[key] = super().__call__(*args)
         return cls._instances[key]
+
+
+def is_test():
+    return (
+        "PYTEST_CURRENT_TEST" in os.environ
+        or "STREAMLIT_GLOBAL_UNIT_TEST" in os.environ
+    )
diff --git a/ptxboa_streamlit.py b/ptxboa_streamlit.py
index 12f79883..aa710229 100644
--- a/ptxboa_streamlit.py
+++ b/ptxboa_streamlit.py
@@ -8,7 +8,6 @@
 
 __version__ = "0.4.2"
 
-# TODO how do I use the treamlit logger?
 import logging
 import warnings
 
@@ -44,6 +43,11 @@
         r"through chained assignment using an inplace method.*"
     ),
 )
+warnings.filterwarnings(  # filter DeprecationWarning for read network
+    action="ignore",
+    category=DeprecationWarning,
+)
+
 
 # setup logging
 # level can be changed on strartup with: --logger.level=LEVEL
@@ -167,10 +171,7 @@
 
 # calculate results over different data dimensions:
 costs_per_region = calculate_results_list(
-    api,
-    parameter_to_change="region",
-    parameter_list=None,
-    optimize_flh=False,  # @markushal: use FLH optimizer disabled in region compare
+    api, parameter_to_change="region", parameter_list=None
 )
 costs_per_scenario = calculate_results_list(
     api,
diff --git a/tests/test_ptxboa_streamlit.py b/tests/test_ptxboa_streamlit.py
index 068ae94b..8bbb37cf 100644
--- a/tests/test_ptxboa_streamlit.py
+++ b/tests/test_ptxboa_streamlit.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 """Tests for the streamlit app."""
+
 import pytest
 from streamlit.testing.v1 import AppTest