diff --git a/pytest-plugin-settings/exasol/pytest_plugin_settings/__init__.py b/pytest-plugin-settings/exasol/pytest_plugin_settings/__init__.py
index 2ad83e4..b742fad 100644
--- a/pytest-plugin-settings/exasol/pytest_plugin_settings/__init__.py
+++ b/pytest-plugin-settings/exasol/pytest_plugin_settings/__init__.py
@@ -1,14 +1,10 @@
 import pytest
 from functools import singledispatch
-from collections.abc import Iterable
+from collections.abc import IterableABC as IterableABC
 from collections.abc import MappingView
 from collections import ChainMap
 from dataclasses import dataclass
-from typing import (
-    Generic,
-    Optional,
-    TypeVar,
-)
+from typing import Any, Dict, Generic, Optional, TypeVar, Iterable
 from enum import Enum, auto
 
 
@@ -105,7 +101,7 @@ def help(self) -> str:
 
 
 class Group:
-    def __init__(self, name: str, settings: Iterable[Setting]):
+    def __init__(self, name: str, settings: IterableABC[Setting]):
         group_name = Name.normalize(name)
         self._name = group_name
         self._settings = tuple(
@@ -137,12 +133,22 @@ class Category(Enum):
 
 class Resolver(MappingView):
     def __init__(
-        self, settings: Iterable[Setting], environment=None, cli_arguments=None
+        self,
+        settings: IterableABC[Setting],
+        cli_arguments=None,
+        environment=None,
+        config=None,
     ):
         self._settings = tuple(settings)
         self._default = {s.normalized_name: s.default for s in self._settings}
-        self._env = environment or {}
-        self._cli = cli_arguments or {}
+        self._config = {}
+        self._env = {}
+        self._cli = {}
+
+        self.update(config, Category.ConfigFile)
+        self.update(environment, Category.Environment)
+        self.update(cli_arguments, Category.CommandLine)
+
         self._kwargs = ChainMap(self._cli, self._env, self._default)
 
     def __len__(self):
@@ -158,7 +164,16 @@ def __iter__(self):
     def settings(self):
         return self._kwargs
 
-    def _environment(self, environment):
+    def _update_cli(self, cli_arguments):
+        cli = {
+            setting.normalized_name: getattr(cli_arguments, setting.pytest)
+            for setting in self.options
+            if hasattr(cli_arguments, setting.pytest)
+            and getattr(cli_arguments, setting.pytest) is not None
+        }
+        self._cli.update(cli)
+
+    def _update_environment(self, environment):
         env = {
             setting.normalized_name: setting.type(environment[setting.env])
             for setting in self._settings
@@ -166,24 +181,36 @@ def _environment(self, environment):
         }
         self._env.update(env)
 
-    def _cli(self, cli_arguments):
-        cli = {
-            setting.normalized_name: getattr(cli_arguments, setting.pytest)
-            for setting in self.options
-            if hasattr(cli_arguments, setting.pytest)
-            and getattr(cli_arguments, setting.pytest) is not None
+    def _update_config_file(self, config):
+        cfg = {
+            setting.normalized_name: setting.type(config[setting.ini])
+            for setting in self._settings
+            if setting.ini in config
         }
-        self._cli.update(cli)
+        self._config.update(cfg)
 
     def update(self, mapping, category):
         dispatcher = {
-            Category.Environment: self._environment,
-            Category.CommandLine: self._cli,
+            Category.CommandLine: self._update_cli,
+            Category.Environment: self._update_environment,
+            Category.ConfigFile: self._update_config_file,
         }
         method = dispatcher[category]
         method(mapping)
 
 
+def from_pytest(settings: Iterable[Setting]) -> Dict[str, Any]:
+    pass
+
+
+def from_env(settings: Iterable[Setting]) -> Dict[str, Any]:
+    pass
+
+
+def from_pytest_ini(settings: Iterable[Setting]) -> Dict[str, Any]:
+    pass
+
+
 @singledispatch
 def add_to_pytest_settings(obj, parser):
     raise TypeError("Unsupported type")
@@ -196,7 +223,7 @@ def _(setting: Setting, parser):
 
 
 @add_to_pytest_settings.register
-def _(settings: Iterable, parser):
+def _(settings: IterableABC, parser):
     for setting in settings:
         add_to_pytest_settings(setting, parser)
 
diff --git a/pytest-plugin-settings/test/unit/resolver_test.py b/pytest-plugin-settings/test/unit/resolver_test.py
index e69de29..501117d 100644
--- a/pytest-plugin-settings/test/unit/resolver_test.py
+++ b/pytest-plugin-settings/test/unit/resolver_test.py
@@ -0,0 +1,33 @@
+import pytest
+
+
+def test_constructor():
+    pass
+
+
+def test_default():
+    pass
+
+
+def test_config():
+    pass
+
+
+def test_env():
+    pass
+
+
+def test_cli():
+    pass
+
+
+def test_update_config():
+    pass
+
+
+def test_update_environment():
+    pass
+
+
+def test_update_cli():
+    pass