diff --git a/api_testgen/cli/main.py b/api_testgen/cli/main.py
index eada49a..8da570e 100644
--- a/api_testgen/cli/main.py
+++ b/api_testgen/cli/main.py
@@ -238,7 +238,12 @@ def generate_all(
 
 @main.command("auth")
 @click.argument("scheme_name")
-@click.option("--type", "auth_type", type=click.Choice(["apiKey", "bearer", "basic"]), help="Authentication type")
+@click.option(
+    "--type",
+    "auth_type",
+    type=click.Choice(["apiKey", "bearer", "basic"]),
+    help="Authentication type",
+)
 @click.option("--header", help="Header name for API key", default="X-API-Key")
 @click.option("--token", help="Bearer token or API key value")
 @click.option("--username", help="Username for Basic auth")
diff --git a/api_testgen/core/auth.py b/api_testgen/core/auth.py
index f1bbebb..7f609f5 100644
--- a/api_testgen/core/auth.py
+++ b/api_testgen/core/auth.py
@@ -8,6 +8,7 @@ from .exceptions import AuthConfigError, MissingSecuritySchemeError
 
 class AuthType(str, Enum):
     """Types of authentication."""
+
     API_KEY = "apiKey"
     BEARER = "bearer"
     BASIC = "basic"
@@ -131,6 +132,7 @@ class AuthConfig:
             return {"Authorization": f"{method['token_prefix']} {method['token']}"}
         elif method["type"] == AuthType.BASIC:
             import base64
+
             credentials = f"{method['username']}:{method['password']}"
             encoded = base64.b64encode(credentials.encode()).decode()
             return {"Authorization": f"Basic {encoded}"}
@@ -222,19 +224,19 @@ class AuthConfig:
             String containing pytest auth code.
         """
         if method["type"] == AuthType.API_KEY:
-            return f'''
+            return f"""
 @pytest.fixture
 def api_key_headers():
     return {{"{method['header_name']}": "{method['api_key']}"}}
-'''
+"""
         elif method["type"] == AuthType.BEARER:
-            return f'''
+            return f"""
 @pytest.fixture
 def bearer_headers():
     return {{"Authorization": "{method['token_prefix']} {method['token']}"}}
-'''
+"""
         elif method["type"] == AuthType.BASIC:
-            return f'''
+            return f"""
 import base64
 
 @pytest.fixture
@@ -242,7 +244,7 @@ def basic_headers():
     credentials = f"{{"{method['username']}"}}:{{"{method['password']}"}}"
     encoded = base64.b64encode(credentials.encode()).decode()
     return {{"Authorization": f"Basic {{encoded}}"}}
-'''
+"""
         return ""
 
     def _generate_jest_auth(self, method: Dict[str, Any]) -> str:
@@ -255,24 +257,24 @@ def basic_headers():
             String containing Jest auth code.
         """
         if method["type"] == AuthType.API_KEY:
-            return f'''
+            return f"""
 const getApiKeyHeaders = () => ({{
   "{method['header_name']}": process.env.API_KEY || "{method['api_key']}",
 }});
-'''
+"""
         elif method["type"] == AuthType.BEARER:
-            return f'''
+            return f"""
 const getBearerHeaders = () => ({{
   Authorization: `${{process.env.TOKEN_PREFIX || "{method['token_prefix']}"}} ${{process.env.TOKEN || "{method['token']}"}}`,
 }});
-'''
+"""
         elif method["type"] == AuthType.BASIC:
-            return f'''
+            return f"""
 const getBasicHeaders = () => {{
   const credentials = Buffer.from(`${{process.env.USERNAME || "{method['username']}"}}:${{process.env.PASSWORD || "{method['password']}"}}`).toString('base64');
   return {{ Authorization: `Basic ${{credentials}}` }};
 }};
-'''
+"""
         return ""
 
     def _generate_go_auth(self, method: Dict[str, Any]) -> str:
@@ -285,23 +287,23 @@ const getBasicHeaders = () => {{
             String containing Go auth code.
         """
         if method["type"] == AuthType.API_KEY:
-            return f'''
+            return f"""
 func getAPIKeyHeaders() map[string]string {{
     return map[string]string{{
         "{method['header_name']}": os.Getenv("API_KEY"),
     }}
 }}
-'''
+"""
         elif method["type"] == AuthType.BEARER:
-            return '''
+            return """
 func getBearerHeaders() map[string]string {
     return map[string]string{
         "Authorization": fmt.Sprintf("%s %s", os.Getenv("TOKEN_PREFIX"), os.Getenv("TOKEN")),
     }
 }
-'''
+"""
         elif method["type"] == AuthType.BASIC:
-            return '''
+            return """
 func getBasicHeaders(username, password string) map[string]string {
     auth := username + ":" + password
     encoded := base64.StdEncoding.EncodeToString([]byte(auth))
@@ -309,5 +311,5 @@ func getBasicHeaders(username, password string) map[string]string {
         "Authorization": "Basic " + encoded,
     }
 }
-'''
+"""
         return ""
diff --git a/api_testgen/core/exceptions.py b/api_testgen/core/exceptions.py
index 5f55cc4..7ae64bd 100644
--- a/api_testgen/core/exceptions.py
+++ b/api_testgen/core/exceptions.py
@@ -3,34 +3,41 @@
 
 class SpecParserError(Exception):
     """Base exception for spec parser errors."""
+
     pass
 
 
 class InvalidOpenAPISpecError(SpecParserError):
     """Raised when OpenAPI specification is invalid."""
+
     pass
 
 
 class UnsupportedVersionError(SpecParserError):
     """Raised when OpenAPI version is not supported."""
+
     pass
 
 
 class AuthConfigError(Exception):
     """Base exception for auth configuration errors."""
+
     pass
 
 
 class MissingSecuritySchemeError(AuthConfigError):
     """Raised when security scheme is not defined in spec."""
+
     pass
 
 
 class GeneratorError(Exception):
     """Base exception for generator errors."""
+
     pass
 
 
 class TemplateRenderError(GeneratorError):
     """Raised when template rendering fails."""
+
     pass
diff --git a/api_testgen/core/spec_parser.py b/api_testgen/core/spec_parser.py
index aab1047..0ec8cc1 100644
--- a/api_testgen/core/spec_parser.py
+++ b/api_testgen/core/spec_parser.py
@@ -55,10 +55,10 @@ class SpecParser:
             raise InvalidOpenAPISpecError(f"Specification file not found: {self.spec_path}")
 
         try:
-            with open(self.spec_path, 'r', encoding='utf-8') as f:
-                if self.spec_path.suffix in ['.yaml', '.yml']:
+            with open(self.spec_path, "r", encoding="utf-8") as f:
+                if self.spec_path.suffix in [".yaml", ".yml"]:
                     return yaml.safe_load(f) or {}
-                elif self.spec_path.suffix == '.json':
+                elif self.spec_path.suffix == ".json":
                     return json.load(f)
                 else:
                     return yaml.safe_load(f) or {}
diff --git a/api_testgen/generators/go.py b/api_testgen/generators/go.py
index 33ccd3c..3a138aa 100644
--- a/api_testgen/generators/go.py
+++ b/api_testgen/generators/go.py
@@ -86,7 +86,9 @@ class GoGenerator:
 
         return generated_files
 
-    def _group_endpoints_by_path(self, endpoints: List[Dict[str, Any]]) -> Dict[str, List[Dict[str, Any]]]:
+    def _group_endpoints_by_path(
+        self, endpoints: List[Dict[str, Any]]
+    ) -> Dict[str, List[Dict[str, Any]]]:
         """Group endpoints by their path.
 
         Args:
@@ -133,7 +135,7 @@ class GoGenerator:
         test_name = self._generate_test_name(endpoint)
         params = self._generate_params(endpoint)
 
-        test_code = f'''
+        test_code = f"""
 func Test{test_name}(t *testing.T) {{
     client := &http.Client{{Timeout: 10 * time.Second}}
     url := baseURL + "{endpoint['path']}"
@@ -162,7 +164,7 @@ func Test{test_name}(t *testing.T) {{
         t.Errorf("Expected status code in [200, 201, 204], got %d", resp.StatusCode)
     }}
 }}
-'''
+"""
         return test_code
 
     def _generate_test_name(self, endpoint: Dict[str, Any]) -> str:
@@ -200,7 +202,15 @@ func Test{test_name}(t *testing.T) {{
 
             if param["in"] == "path":
                 params.append(f'{param_name} := "test_{param_name}"')
-                params.append('url = strings.Replace(url, "' + '{' + param_name + '}' + '", ' + param_name + ', 1)')
+                params.append(
+                    'url = strings.Replace(url, "'
+                    + "{"
+                    + param_name
+                    + "}"
+                    + '", '
+                    + param_name
+                    + ", 1)"
+                )
 
             elif param["in"] == "query":
                 params.append(f'q := url.Values{{{param_name}: []string{{"test"}}}}')
@@ -222,6 +232,14 @@ func Test{test_name}(t *testing.T) {{
         parts = []
 
         for param in path_params:
-            parts.append('strings.Replace(url, "' + '{' + param['name'] + '}' + '", "test_' + param['name'] + '", 1)')
+            parts.append(
+                'strings.Replace(url, "'
+                + "{"
+                + param["name"]
+                + "}"
+                + '", "test_'
+                + param["name"]
+                + '", 1)'
+            )
 
         return ""
diff --git a/api_testgen/generators/jest.py b/api_testgen/generators/jest.py
index 406b6bf..b56e357 100644
--- a/api_testgen/generators/jest.py
+++ b/api_testgen/generators/jest.py
@@ -30,7 +30,9 @@ class JestGenerator:
         self.output_dir = Path(output_dir)
         self.mock_server_url = mock_server_url
         self.env = Environment(
-            loader=FileSystemLoader(str(Path(__file__).parent.parent.parent / "templates" / "jest")),
+            loader=FileSystemLoader(
+                str(Path(__file__).parent.parent.parent / "templates" / "jest")
+            ),
             trim_blocks=True,
             lstrip_blocks=True,
         )
@@ -113,7 +115,7 @@ class JestGenerator:
         endpoint_path = endpoint["path"]
         endpoint_method = endpoint["method"]
 
-        test_code = f'''
+        test_code = f"""
 describe('{describe_name}', () => {{
   it('should {endpoint_method.upper()} {endpoint_path}', async () => {{
     const response = await request(baseUrl)
@@ -122,7 +124,7 @@ describe('{describe_name}', () => {{
     expect([200, 201, 204]).toContain(response.status);
   }});
 }});
-'''
+"""
         return test_code
 
     def _generate_test_name(self, endpoint: Dict[str, Any]) -> str:
@@ -161,7 +163,7 @@ describe('{describe_name}', () => {{
                 parts.append(f'{param_name}="test_{param_name}"')
 
             elif param["in"] == "query":
-                parts.append(f'{param_name}')
+                parts.append(f"{param_name}")
 
         if parts:
             return ", {" + ", ".join(parts) + "}"
diff --git a/api_testgen/generators/pytest.py b/api_testgen/generators/pytest.py
index 83504f0..c50cbc9 100644
--- a/api_testgen/generators/pytest.py
+++ b/api_testgen/generators/pytest.py
@@ -30,7 +30,9 @@ class PytestGenerator:
         self.output_dir = Path(output_dir)
         self.mock_server_url = mock_server_url
         self.env = Environment(
-            loader=FileSystemLoader(str(Path(__file__).parent.parent.parent / "templates" / "pytest")),
+            loader=FileSystemLoader(
+                str(Path(__file__).parent.parent.parent / "templates" / "pytest")
+            ),
             trim_blocks=True,
             lstrip_blocks=True,
         )
@@ -160,7 +162,7 @@ def test_{test_name}(base_url, {params}):
                 params.append(f'{param_name}="test_{param_name}"')
 
             elif param["in"] == "query":
-                params.append(f'{param_name}=None')
+                params.append(f"{param_name}=None")
 
         return ", ".join(params)
 
diff --git a/api_testgen/mocks/generator.py b/api_testgen/mocks/generator.py
index 06cacf0..0c2c3ba 100644
--- a/api_testgen/mocks/generator.py
+++ b/api_testgen/mocks/generator.py
@@ -112,7 +112,7 @@ class MockServerGenerator:
 
         spec_info = self.spec_parser.get_info()
 
-        compose_content = f'''version: '3.8'
+        compose_content = f"""version: '3.8'
 
 services:
   mock-server:
@@ -147,7 +147,7 @@ services:
     volumes:
       - ./:/app
     restart: unless-stopped
-'''
+"""
 
         output_path.write_text(compose_content)
         return output_path
@@ -168,7 +168,7 @@ services:
 
         spec_info = self.spec_parser.get_info()
 
-        dockerfile_content = f'''FROM stoplight/prism:latest
+        dockerfile_content = f"""FROM stoplight/prism:latest
 
 LABEL maintainer="developer@example.com"
 LABEL description="Mock server for {spec_info['title']} API"
@@ -180,7 +180,7 @@ COPY openapi.yaml .
 EXPOSE {self.DEFAULT_PORT}
 
 CMD ["mock", "--spec", "openapi.yaml", "--port", "{self.DEFAULT_PORT}", "--host", "0.0.0.0"]
-'''
+"""
 
         output_path.write_text(dockerfile_content)
         return output_path
@@ -199,7 +199,7 @@ CMD ["mock", "--spec", "openapi.yaml", "--port", "{self.DEFAULT_PORT}", "--host"
         else:
             output_path = self.output_dir / "start-mock-server.sh"
 
-        script_content = f'''#!/bin/bash
+        script_content = f"""#!/bin/bash
 
 set -e
 
@@ -216,7 +216,7 @@ docker compose up -d mock-server
 
 echo "Mock server started successfully!"
 echo "To stop: docker compose down"
-'''
+"""
 
         output_path.write_text(script_content)
         output_path.chmod(0o755)