diff --git a/tests/test_scanners.py b/tests/test_scanners.py
new file mode 100644
index 0000000..68a3b0e
--- /dev/null
+++ b/tests/test_scanners.py
@@ -0,0 +1,131 @@
+"""Tests for string scanner."""
+
+import pytest
+
+from i18n_guardian.scanners.string_scanner import StringScanner, ScanResult
+
+
+class TestStringScanner:
+    """Tests for StringScanner."""
+
+    def test_scan_python_file(self, sample_python_file):
+        """Test scanning a Python file."""
+        scanner = StringScanner(min_length=3)
+        result = scanner.scan(sample_python_file.parent)
+
+        assert result.files_scanned >= 1
+        assert result.strings_found > 0
+        assert isinstance(result, ScanResult)
+
+    def test_scan_js_file(self, sample_js_file):
+        """Test scanning a JavaScript file."""
+        scanner = StringScanner(min_length=3)
+        result = scanner.scan(sample_js_file.parent)
+
+        assert result.files_scanned >= 1
+
+    def test_min_length_filter(self, temp_dir):
+        """Test minimum length filter."""
+        py_file = temp_dir / "test.py"
+        py_file.write_text('a = "x"\nb = "longer string here"', encoding="utf-8")
+
+        scanner = StringScanner(min_length=5)
+        result = scanner.scan(temp_dir)
+
+        assert result.strings_found >= 1
+
+    def test_url_exclusion(self, temp_dir):
+        """Test that URLs are excluded."""
+        py_file = temp_dir / "test.py"
+        py_file.write_text('url = "https://example.com/path"', encoding="utf-8")
+
+        scanner = StringScanner(min_length=3)
+        result = scanner.scan(temp_dir)
+
+        violations = [v for v in result.violations if "https://" in v.literal.value]
+        assert len(violations) == 0
+
+    def test_email_exclusion(self, temp_dir):
+        """Test that emails are excluded."""
+        py_file = temp_dir / "test.py"
+        py_file.write_text('email = "test@example.com"', encoding="utf-8")
+
+        scanner = StringScanner(min_length=3)
+        result = scanner.scan(temp_dir)
+
+        violations = [v for v in result.violations if "test@example.com" in v.literal.value]
+        assert len(violations) == 0
+
+    def test_regex_exclusion(self, temp_dir):
+        """Test that regex patterns are excluded."""
+        py_file = temp_dir / "test.py"
+        py_file.write_text('pattern = r"^test\\d+$"', encoding="utf-8")
+
+        scanner = StringScanner(min_length=3)
+        result = scanner.scan(temp_dir)
+
+        assert result.violations_count == 0
+
+    def test_exclude_patterns(self, temp_dir):
+        """Test exclusion patterns."""
+        node_modules = temp_dir / "node_modules"
+        node_modules.mkdir()
+        test_file = node_modules / "test.js"
+        test_file.write_text('message = "Hardcoded string"', encoding="utf-8")
+
+        src_dir = temp_dir / "src"
+        src_dir.mkdir()
+        src_file = src_dir / "test.js"
+        src_file.write_text('message = "Hardcoded string"', encoding="utf-8")
+
+        scanner = StringScanner(
+            min_length=3,
+            exclude_patterns=["**/node_modules/**"],
+        )
+        result = scanner.scan(temp_dir)
+
+        for violation in result.violations:
+            assert "node_modules" not in str(violation.literal.file_path)
+
+    def test_i18n_function_exclusion(self, sample_js_file):
+        """Test that i18n function calls are excluded."""
+        scanner = StringScanner(
+            min_length=3,
+            i18n_functions=["t", "formatMessage"],
+        )
+        result = scanner.scan(sample_js_file.parent)
+
+        for violation in result.violations:
+            if violation.literal.value.startswith("t("):
+                pytest.skip("Function call detected")
+
+    def test_key_generation(self, sample_python_file):
+        """Test that keys are generated for violations."""
+        scanner = StringScanner(min_length=3)
+        result = scanner.scan(sample_python_file.parent)
+
+        for violation in result.violations:
+            assert violation.suggested_key is not None
+            assert len(violation.suggested_key) > 0
+
+    def test_scan_result_structure(self, sample_python_file):
+        """Test ScanResult has correct structure."""
+        scanner = StringScanner(min_length=3)
+        result = scanner.scan(sample_python_file.parent)
+
+        assert hasattr(result, "violations")
+        assert hasattr(result, "files_scanned")
+        assert hasattr(result, "strings_found")
+        assert hasattr(result, "violations_count")
+        assert isinstance(result.violations, list)
+
+    def test_violation_structure(self, sample_python_file):
+        """Test Violation has correct structure."""
+        scanner = StringScanner(min_length=3)
+        result = scanner.scan(sample_python_file.parent)
+
+        if result.violations:
+            violation = result.violations[0]
+            assert hasattr(violation, "literal")
+            assert hasattr(violation, "suggested_key")
+            assert hasattr(violation, "reason")