diff --git a/tests/test_config.py b/tests/test_config.py
new file mode 100644
index 0000000..0143fda
--- /dev/null
+++ b/tests/test_config.py
@@ -0,0 +1,89 @@
+"""Тесты модуля конфигурации."""
+
+from __future__ import annotations
+
+from selectel_ml_tui.config import (
+    Credentials,
+    Settings,
+    load_credentials,
+    load_settings,
+    save_credentials,
+    save_settings,
+)
+
+
+def test_settings_defaults() -> None:
+    settings = load_settings()
+    assert settings.api_base_url == "https://api.selectel.ru"
+    assert settings.refresh_interval >= 10
+
+
+def test_save_settings_roundtrip(tmp_path, monkeypatch) -> None:
+    cfg_file = tmp_path / "config.toml"
+    monkeypatch.setattr("selectel_ml_tui.config._config_file", lambda: cfg_file)
+    settings = Settings(router_id="gw-test", refresh_interval=30)
+    save_settings(settings)
+    loaded = load_settings()
+    assert loaded.router_id == "gw-test"
+    assert loaded.refresh_interval == 30
+
+
+def test_load_settings_repairs_small_interval(tmp_path, monkeypatch) -> None:
+    cfg_file = tmp_path / "config.toml"
+    cfg_file.write_text("refresh_interval = 5\n", encoding="utf-8")
+    monkeypatch.setattr("selectel_ml_tui.config._config_file", lambda: cfg_file)
+    settings = load_settings()
+    assert settings.refresh_interval == 10
+
+
+def test_load_settings_repairs_garbage_interval(tmp_path, monkeypatch) -> None:
+    cfg_file = tmp_path / "config.toml"
+    cfg_file.write_text('refresh_interval = "abc"\n', encoding="utf-8")
+    monkeypatch.setattr("selectel_ml_tui.config._config_file", lambda: cfg_file)
+    settings = load_settings()
+    assert settings.refresh_interval == 60
+
+
+def test_load_settings_ignores_bad_env_interval(tmp_path, monkeypatch) -> None:
+    cfg_file = tmp_path / "config.toml"
+    monkeypatch.setattr("selectel_ml_tui.config._config_file", lambda: cfg_file)
+    monkeypatch.setenv("SELCTEL_REFRESH_INTERVAL", "5")
+    settings = load_settings()
+    assert settings.refresh_interval == 60
+
+
+def test_credentials_defaults() -> None:
+    creds = Credentials()
+    assert creds.service_user == ""
+    assert creds.static_token == ""
+
+
+def test_settings_env_api_url(monkeypatch, tmp_path) -> None:
+    cfg_file = tmp_path / "config.toml"
+    monkeypatch.setattr("selectel_ml_tui.config._config_file", lambda: cfg_file)
+    monkeypatch.setenv("SELCTEL_API_URL", "https://api.example.test")
+    settings = load_settings()
+    assert settings.api_base_url == "https://api.example.test"
+
+
+def test_credentials_env(monkeypatch, tmp_path) -> None:
+    cred_file = tmp_path / "credentials.json"
+    monkeypatch.setattr("selectel_ml_tui.config._credentials_file", lambda: cred_file)
+    monkeypatch.setenv("SELCTEL_TOKEN", "tok123")
+    monkeypatch.setenv("SELCTEL_SERVICE_USER", "svc-user")
+    monkeypatch.setenv("SELCTEL_DOMAIN_ID", "239633")
+    creds = load_credentials()
+    assert creds.static_token == "tok123"
+    assert creds.service_user == "svc-user"
+    assert creds.domain_id == "239633"
+
+
+def test_credentials_file_precedence(monkeypatch, tmp_path) -> None:
+    cred_file = tmp_path / "credentials.json"
+    monkeypatch.setattr("selectel_ml_tui.config._credentials_file", lambda: cred_file)
+    save_credentials(Credentials(static_token="from-file", service_user="file-user"))
+    monkeypatch.setenv("SELCTEL_TOKEN", "from-env")
+    creds = load_credentials()
+    # env имеет приоритет над файлом
+    assert creds.static_token == "from-env"
+    assert creds.service_user == "file-user"