diff --git a/lib/dl_connector_bigquery/dl_connector_bigquery/testing/secrets.py b/lib/dl_connector_bigquery/dl_connector_bigquery/testing/secrets.py
index a17ae1fb2..e14c27b5d 100644
--- a/lib/dl_connector_bigquery/dl_connector_bigquery/testing/secrets.py
+++ b/lib/dl_connector_bigquery/dl_connector_bigquery/testing/secrets.py
@@ -36,11 +36,11 @@ class BigQuerySecretReader(BigQuerySecretReaderBase):
 
     @_project_config.default
     def _make_project_config(self) -> dict:
-        return self._env_param_getter.get_json_value(self.KEY_CONFIG)
+        return self._env_param_getter.get_json_value_strict(self.KEY_CONFIG)
 
     @property
     def project_config(self) -> dict:
         return self._project_config
 
     def get_creds(self) -> str:
-        return self._env_param_getter.get_str_value(self.KEY_CREDS)
+        return self._env_param_getter.get_str_value_strict(self.KEY_CREDS)
diff --git a/lib/dl_connector_snowflake/dl_connector_snowflake/core/testing/secrets.py b/lib/dl_connector_snowflake/dl_connector_snowflake/core/testing/secrets.py
index c35b87b50..4de19ca6b 100644
--- a/lib/dl_connector_snowflake/dl_connector_snowflake/core/testing/secrets.py
+++ b/lib/dl_connector_snowflake/dl_connector_snowflake/core/testing/secrets.py
@@ -64,17 +64,17 @@ class SnowFlakeSecretReader(SnowFlakeSecretReaderBase):
 
     @_project_config.default
     def _make_project_config(self) -> dict:
-        return self._env_param_getter.get_json_value(self.KEY_CONFIG)
+        return self._env_param_getter.get_json_value_strict(self.KEY_CONFIG)
 
     @property
     def project_config(self) -> dict:
         return self._project_config
 
     def get_client_secret(self) -> str:
-        return self._env_param_getter.get_str_value(self.KEY_CLIENT_SECRET)
+        return self._env_param_getter.get_str_value_strict(self.KEY_CLIENT_SECRET)
 
     def get_refresh_token_expired(self) -> str:
-        return self._env_param_getter.get_str_value(self.KEY_REFRESH_TOKEN_EXPIRED)
+        return self._env_param_getter.get_str_value_strict(self.KEY_REFRESH_TOKEN_EXPIRED)
 
     def get_refresh_token_x(self) -> str:
-        return self._env_param_getter.get_str_value(self.KEY_REFRESH_TOKEN_X)
+        return self._env_param_getter.get_str_value_strict(self.KEY_REFRESH_TOKEN_X)
diff --git a/lib/dl_testing/dl_testing/env_params/generic.py b/lib/dl_testing/dl_testing/env_params/generic.py
index 306555893..16e9c14e1 100644
--- a/lib/dl_testing/dl_testing/env_params/generic.py
+++ b/lib/dl_testing/dl_testing/env_params/generic.py
@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+from typing import Optional
+
 import attr
 import yaml
 
@@ -12,7 +14,7 @@ class GenericEnvParamGetter(EnvParamGetter):
     _loader: EnvParamGetterLoader = attr.ib(init=False, factory=EnvParamGetterLoader)
     _key_mapping: dict[str, tuple[str, str]] = attr.ib(init=False, factory=dict)  # key -> (getter_name, remapped_key)
 
-    def get_str_value(self, key: str) -> str:
+    def get_str_value(self, key: str) -> Optional[str]:
         getter_name, remapped_key = self._key_mapping[key]
         getter = self._loader.get_getter(getter_name)
         value = getter.get_str_value(remapped_key)
diff --git a/lib/dl_testing/dl_testing/env_params/getter.py b/lib/dl_testing/dl_testing/env_params/getter.py
index f97923050..a4d859ef3 100644
--- a/lib/dl_testing/dl_testing/env_params/getter.py
+++ b/lib/dl_testing/dl_testing/env_params/getter.py
@@ -2,26 +2,65 @@
 
 import abc
 import json
+from typing import (
+    NoReturn,
+    Optional,
+)
 
 import yaml
 
 
+def _raise_error_no_key(key: str) -> NoReturn:
+    raise ValueError(f"Key {key!r} is missing")
+
+
 class EnvParamGetter(abc.ABC):
     @abc.abstractmethod
-    def get_str_value(self, key: str) -> str:
+    def get_str_value(self, key: str) -> Optional[str]:
         raise NotImplementedError
 
-    def get_int_value(self, key: str) -> int:
+    def get_str_value_strict(self, key: str) -> str:
+        str_value = self.get_str_value(key)
+        if str_value is None:
+            _raise_error_no_key(key)
+        return str_value
+
+    def get_int_value(self, key: str) -> Optional[int]:
         str_value = self.get_str_value(key)
-        return int(str_value)
+        if str_value is not None:
+            return int(str_value)
+        return None
 
-    def get_json_value(self, key: str) -> dict:
+    def get_int_value_strict(self, key: str) -> int:
+        int_value = self.get_int_value(key)
+        if int_value is None:
+            _raise_error_no_key(key)
+        return int_value
+
+    def get_json_value(self, key: str) -> Optional[dict]:
         str_value = self.get_str_value(key)
-        return json.loads(str_value)
+        if str_value is not None:
+            return json.loads(str_value)
+        return None
+
+    def get_json_value_strict(self, key: str) -> dict:
+        json_value = self.get_json_value(key)
+        if json_value is None:
+            _raise_error_no_key(key)
+        return json_value
 
-    def get_yaml_value(self, key: str) -> dict:
+    def get_yaml_value(self, key: str) -> Optional[dict]:
         str_value = self.get_str_value(key)
-        return yaml.safe_load(str_value)
+        if str_value is not None:
+            return yaml.safe_load(str_value)
+        return None
 
+    def get_yaml_value_strict(self, key: str) -> dict:
+        yaml_value = self.get_yaml_value(key)
+        if yaml_value is None:
+            _raise_error_no_key(key)
+        return yaml_value
+
+    @abc.abstractmethod
     def initialize(self, config: dict) -> None:
         pass
diff --git a/lib/dl_testing/dl_testing/env_params/loader.py b/lib/dl_testing/dl_testing/env_params/loader.py
index 21e1e02bb..83224cb31 100644
--- a/lib/dl_testing/dl_testing/env_params/loader.py
+++ b/lib/dl_testing/dl_testing/env_params/loader.py
@@ -1,6 +1,7 @@
 from typing import (
     ClassVar,
     Mapping,
+    Optional,
     Sequence,
 )
 
@@ -40,7 +41,7 @@ def _auto_add_getter(self, name: str) -> None:
         getter.initialize(config={})
         self._getters[name] = getter
 
-    def _resolve_setting_item(self, setting: dict, requirement_getter: EnvParamGetter) -> str:
+    def _resolve_setting_item(self, setting: dict, requirement_getter: EnvParamGetter) -> Optional[str]:
         if setting["type"] == "value":
             return setting["value"]
         if setting["type"] == "param":
diff --git a/lib/dl_testing/dl_testing/env_params/main.py b/lib/dl_testing/dl_testing/env_params/main.py
index 7d02f2acf..981fc20c7 100644
--- a/lib/dl_testing/dl_testing/env_params/main.py
+++ b/lib/dl_testing/dl_testing/env_params/main.py
@@ -1,4 +1,5 @@
 import os
+from typing import Optional
 
 import attr
 from dotenv import (
@@ -15,6 +16,9 @@ class DirectEnvParamGetter(EnvParamGetter):
     def get_str_value(self, key: str) -> str:
         return str(key)
 
+    def initialize(self, config: dict) -> None:
+        pass
+
 
 @attr.s
 class OsEnvParamGetter(EnvParamGetter):
@@ -26,7 +30,7 @@ def initialize(self, config: dict) -> None:
         env_file = os.environ.get("DL_TESTS_ENV_FILE") or find_dotenv(filename=".env")
         self._env_from_file = dotenv_values(env_file)
 
-    def get_str_value(self, key: str) -> str:
+    def get_str_value(self, key: str) -> Optional[str]:
         env_value = os.environ.get(key)
 
         if env_value is None:
diff --git a/lib/dl_testing/dl_testing/regulated_test.py b/lib/dl_testing/dl_testing/regulated_test.py
index 8bece74d4..081e99d78 100644
--- a/lib/dl_testing/dl_testing/regulated_test.py
+++ b/lib/dl_testing/dl_testing/regulated_test.py
@@ -193,7 +193,9 @@ def regulated_test_case(test_cls: type, /) -> type:
 
 
 @overload
-def regulated_test_case(*, test_params: RegulatedTestParams = RegulatedTestParams()) -> Callable[[type], type]:
+def regulated_test_case(
+    *, test_params: RegulatedTestParams = RegulatedTestParams()  # noqa B008
+) -> Callable[[type], type]:
     ...