diff --git a/tests/test_keygen.py b/tests/test_keygen.py
new file mode 100644
index 0000000..e2ec4ec
--- /dev/null
+++ b/tests/test_keygen.py
@@ -0,0 +1,127 @@
+"""Tests for key generation."""
+
+from pathlib import Path
+
+
+from i18n_guardian.keygen.key_generator import KeyGenerator, analyze_existing_keys
+
+
+class TestKeyGenerator:
+    """Tests for KeyGenerator."""
+
+    def test_snake_case_conversion(self):
+        """Test snake_case key generation."""
+        generator = KeyGenerator(style="snake_case")
+        key = generator.generate_key("Hello World")
+        assert key == "hello_world"
+
+    def test_kebab_case_conversion(self):
+        """Test kebab-case key generation."""
+        generator = KeyGenerator(style="kebab-case")
+        key = generator.generate_key("Hello World")
+        assert key == "hello-world"
+
+    def test_camel_case_conversion(self):
+        """Test camelCase key generation."""
+        generator = KeyGenerator(style="camelCase")
+        key = generator.generate_key("Hello World")
+        assert key == "helloWorld"
+
+    def test_pascal_case_conversion(self):
+        """Test PascalCase key generation."""
+        generator = KeyGenerator(style="PascalCase")
+        key = generator.generate_key("hello world")
+        assert key == "HelloWorld"
+
+    def test_prefix_support(self):
+        """Test key prefix."""
+        generator = KeyGenerator(prefix="common")
+        key = generator.generate_key("Hello")
+        assert key.startswith("common_")
+
+    def test_max_length(self):
+        """Test max length constraint."""
+        generator = KeyGenerator(max_length=10)
+        key = generator.generate_key("This is a very long text that should be truncated")
+        assert len(key) <= 10
+
+    def test_special_characters(self):
+        """Test handling of special characters."""
+        generator = KeyGenerator(style="snake_case")
+        key = generator.generate_key("Hello! @#$ World")
+        assert "!" not in key
+        assert "@" not in key
+        assert "#" not in key
+        assert "$" not in key
+
+    def test_duplicate_key_handling(self):
+        """Test that duplicate keys get unique suffixes."""
+        generator = KeyGenerator(style="snake_case")
+        generator.set_existing_keys(["hello_world"])
+
+        key1 = generator.generate_key("Hello World")
+        key2 = generator.generate_key("Hello World")
+
+        assert key1 != key2
+        assert "hello_world" in key1 or "hello_world" in key2
+
+    def test_path_prefix(self, temp_dir):
+        """Test path-based prefix generation."""
+        generator = KeyGenerator(style="snake_case")
+        file_path = temp_dir / "components" / "Button.tsx"
+        key = generator.generate_key("Submit", file_path=file_path)
+        assert "button" in key.lower() or "submit" in key.lower()
+
+    def test_context_adding(self):
+        """Test context-based key generation."""
+        generator = KeyGenerator(style="snake_case")
+        key = generator.generate_key("Submit", context="button")
+        assert "submit" in key.lower()
+        assert "button" in key.lower()
+
+    def test_numeric_exclusion(self):
+        """Test that numeric-only strings are handled."""
+        generator = KeyGenerator(style="snake_case")
+        key = generator.generate_key("12345")
+        assert key.isdigit() or key == ""
+
+    def test_whitespace_handling(self):
+        """Test handling of whitespace."""
+        generator = KeyGenerator(style="snake_case")
+        key = generator.generate_key("  Hello   World  ")
+        assert "  " not in key
+        assert key == "hello_world"
+
+
+class TestAnalyzeExistingKeys:
+    """Tests for analyzing existing translation keys."""
+
+    def test_analyze_json_keys(self, temp_dir):
+        """Test analyzing JSON translation files."""
+        locales_dir = temp_dir / "locales"
+        locales_dir.mkdir()
+
+        en_json = locales_dir / "en.json"
+        en_json.write_text('{"greeting": "Hello", "farewell": "Goodbye"}', encoding="utf-8")
+
+        keys = analyze_existing_keys(en_json)
+        assert "greeting" in keys
+        assert "farewell" in keys
+
+    def test_analyze_nested_json_keys(self, temp_dir):
+        """Test analyzing nested JSON translation files."""
+        locales_dir = temp_dir / "locales"
+        locales_dir.mkdir()
+
+        en_json = locales_dir / "en.json"
+        en_json.write_text(
+            '{"buttons": {"submit": "Submit", "cancel": "Cancel"}}', encoding="utf-8"
+        )
+
+        keys = analyze_existing_keys(en_json)
+        assert any("buttons" in k for k in keys)
+
+    def test_missing_file(self):
+        """Test handling of missing files."""
+        keys = analyze_existing_keys(Path("/nonexistent/file.json"))
+        assert keys == []