diff --git a/tests/test_detectors.py b/tests/test_detectors.py
new file mode 100644
index 0000000..9ce0a95
--- /dev/null
+++ b/tests/test_detectors.py
@@ -0,0 +1,139 @@
+"""Tests for detectors."""
+
+
+
+from i18n_guardian.detectors.base import get_default_registry
+
+
+class TestReactIntlDetector:
+    """Tests for React Intl detector."""
+
+    def test_detect_react_intl_in_package_json(self, temp_dir):
+        """Test detection of react-intl in package.json."""
+        package_json = temp_dir / "package.json"
+        package_json.write_text('{"dependencies": {"react-intl": "^5.0.0"}}', encoding="utf-8")
+
+        registry = get_default_registry()
+        detector = registry.get("react-intl")
+        assert detector is not None
+        assert detector.detect(temp_dir) == "react-intl"
+
+    def test_detect_react_intl_in_imports(self, temp_dir):
+        """Test detection of react-intl in source imports."""
+        js_file = temp_dir / "App.js"
+        js_file.write_text("import { defineMessages } from 'react-intl'", encoding="utf-8")
+
+        registry = get_default_registry()
+        detector = registry.get("react-intl")
+        assert detector is not None
+        assert detector.detect(temp_dir) == "react-intl"
+
+    def test_get_react_intl_functions(self, temp_dir):
+        """Test getting react-intl function names."""
+        registry = get_default_registry()
+        detector = registry.get("react-intl")
+        assert detector is not None
+        functions = detector.get_i18n_functions()
+        assert "formatMessage" in functions
+        assert "defineMessages" in functions
+
+
+class TestI18NextDetector:
+    """Tests for i18next detector."""
+
+    def test_detect_i18next_in_package_json(self, temp_dir):
+        """Test detection of i18next in package.json."""
+        package_json = temp_dir / "package.json"
+        package_json.write_text('{"dependencies": {"i18next": "^21.0.0"}}', encoding="utf-8")
+
+        registry = get_default_registry()
+        detector = registry.get("i18next")
+        assert detector is not None
+        assert detector.detect(temp_dir) == "i18next"
+
+    def test_detect_i18next_in_locales(self, temp_dir):
+        """Test detection of i18next via locale files."""
+        locales_dir = temp_dir / "locales"
+        locales_dir.mkdir()
+        en_json = locales_dir / "en.json"
+        en_json.write_text('{"greeting": "Hello"}', encoding="utf-8")
+
+        registry = get_default_registry()
+        detector = registry.get("i18next")
+        assert detector is not None
+        result = detector.detect(temp_dir)
+        assert result == "i18next"
+
+
+class TestVueI18nDetector:
+    """Tests for Vue I18n detector."""
+
+    def test_detect_vue_i18n_in_package_json(self, temp_dir):
+        """Test detection of vue-i18n in package.json."""
+        package_json = temp_dir / "package.json"
+        package_json.write_text('{"dependencies": {"vue-i18n": "^8.0.0"}}', encoding="utf-8")
+
+        registry = get_default_registry()
+        detector = registry.get("vue-i18n")
+        assert detector is not None
+        assert detector.detect(temp_dir) == "vue-i18n"
+
+
+class TestGettextDetector:
+    """Tests for Gettext detector."""
+
+    def test_detect_gettext_po_files(self, temp_dir):
+        """Test detection of gettext via .po files."""
+        po_file = temp_dir / "messages.po"
+        po_file.write_text('msgid "Hello"\nmsgstr "Hallo"', encoding="utf-8")
+
+        registry = get_default_registry()
+        detector = registry.get("gettext")
+        assert detector is not None
+        assert detector.detect(temp_dir) == "gettext"
+
+
+class TestPythonGettextDetector:
+    """Tests for Python gettext detector."""
+
+    def test_detect_python_gettext_imports(self, temp_dir):
+        """Test detection of Python gettext via imports."""
+        py_file = temp_dir / "app.py"
+        py_file.write_text("import gettext\n_ = gettext.gettext", encoding="utf-8")
+
+        registry = get_default_registry()
+        detector = registry.get("python-gettext")
+        assert detector is not None
+        assert detector.detect(temp_dir) == "python-gettext"
+
+
+class TestDetectorRegistry:
+    """Tests for detector registry."""
+
+    def test_list_detectors(self):
+        """Test listing all detectors."""
+        registry = get_default_registry()
+        detectors = registry.list_detectors()
+        assert "react-intl" in detectors
+        assert "i18next" in detectors
+        assert "vue-i18n" in detectors
+        assert "gettext" in detectors
+        assert "python-gettext" in detectors
+
+    def test_detect_library_auto(self, temp_dir):
+        """Test auto-detection of i18n library."""
+        package_json = temp_dir / "package.json"
+        package_json.write_text('{"dependencies": {"i18next": "^21.0.0"}}', encoding="utf-8")
+
+        registry = get_default_registry()
+        detected = registry.detect_library(temp_dir)
+        assert detected == "i18next"
+
+    def test_detect_no_library(self, temp_dir):
+        """Test when no i18n library is found."""
+        py_file = temp_dir / "app.py"
+        py_file.write_text("print('Hello')", encoding="utf-8")
+
+        registry = get_default_registry()
+        detected = registry.detect_library(temp_dir)
+        assert detected is None