diff --git a/tests/unit/test_auth.py b/tests/unit/test_auth.py
new file mode 100644
index 0000000..1b60b1e
--- /dev/null
+++ b/tests/unit/test_auth.py
@@ -0,0 +1,182 @@
+"""Unit tests for the auth configuration module."""
+import pytest
+import tempfile
+from pathlib import Path
+
+from api_testgen.core.auth import AuthConfig, AuthType
+from api_testgen.core.exceptions import AuthConfigError, MissingSecuritySchemeError
+
+
+class TestAuthConfig:
+    """Tests for AuthConfig class."""
+
+    def test_add_api_key(self):
+        """Test adding API key authentication."""
+        auth = AuthConfig()
+        auth.add_api_key("test_api_key", header_name="X-API-Key", api_key="test123")
+
+        method = auth.get_auth_method("test_api_key")
+
+        assert method is not None
+        assert method["type"] == AuthType.API_KEY
+        assert method["header_name"] == "X-API-Key"
+        assert method["api_key"] == "test123"
+
+    def test_add_bearer_token(self):
+        """Test adding Bearer token authentication."""
+        auth = AuthConfig()
+        auth.add_bearer("test_bearer", token="abc123", token_prefix="Bearer")
+
+        method = auth.get_auth_method("test_bearer")
+
+        assert method is not None
+        assert method["type"] == AuthType.BEARER
+        assert method["token"] == "abc123"
+        assert method["token_prefix"] == "Bearer"
+
+    def test_add_basic_auth(self):
+        """Test adding Basic authentication."""
+        auth = AuthConfig()
+        auth.add_basic("test_basic", username="user", password="pass")
+
+        method = auth.get_auth_method("test_basic")
+
+        assert method is not None
+        assert method["type"] == AuthType.BASIC
+        assert method["username"] == "user"
+        assert method["password"] == "pass"
+
+    def test_method_chaining(self):
+        """Test that add methods return self for chaining."""
+        auth = AuthConfig()
+
+        result = auth.add_api_key("key1")
+        assert result is auth
+
+        result = auth.add_bearer("key2")
+        assert result is auth
+
+        result = auth.add_basic("key3")
+        assert result is auth
+
+    def test_get_all_methods(self):
+        """Test getting all configured auth methods."""
+        auth = AuthConfig()
+        auth.add_api_key("api_key")
+        auth.add_bearer("bearer")
+
+        methods = auth.get_all_methods()
+
+        assert len(methods) == 2
+        assert "api_key" in methods
+        assert "bearer" in methods
+
+    def test_get_headers_api_key(self):
+        """Test getting headers for API key auth."""
+        auth = AuthConfig()
+        auth.add_api_key("test", header_name="X-Custom-Key", api_key="mykey")
+
+        headers = auth.get_headers("test")
+
+        assert headers["X-Custom-Key"] == "mykey"
+
+    def test_get_headers_bearer(self):
+        """Test getting headers for Bearer auth."""
+        auth = AuthConfig()
+        auth.add_bearer("test", token="mytoken", token_prefix="Bearer")
+
+        headers = auth.get_headers("test")
+
+        assert headers["Authorization"] == "Bearer mytoken"
+
+    def test_get_headers_basic(self):
+        """Test getting headers for Basic auth."""
+        import base64
+
+        auth = AuthConfig()
+        auth.add_basic("test", username="user", password="pass")
+
+        headers = auth.get_headers("test")
+
+        expected = base64.b64encode(b"user:pass").decode()
+        assert headers["Authorization"] == f"Basic {expected}"
+
+    def test_get_headers_unconfigured_scheme_raises_error(self):
+        """Test that getting headers for unconfigured scheme raises error."""
+        auth = AuthConfig()
+
+        with pytest.raises(AuthConfigError):
+            auth.get_headers("nonexistent")
+
+    def test_build_from_spec(self):
+        """Test building auth config from OpenAPI security schemes."""
+        auth = AuthConfig()
+
+        security_schemes = {{
+            "ApiKeyAuth": {{"type": "apiKey", "name": "X-API-Key", "in": "header"}},
+            "BearerAuth": {{"type": "http", "scheme": "bearer"}},
+            "BasicAuth": {{"type": "http", "scheme": "basic"}},
+        }}
+
+        security_requirements = [
+            {{"ApiKeyAuth": []}},
+            {{"BearerAuth": []}},
+        ]
+
+        auth.build_from_spec(security_schemes, security_requirements)
+
+        assert auth.get_auth_method("ApiKeyAuth") is not None
+        assert auth.get_auth_method("BearerAuth") is not None
+        assert auth.get_auth_method("BasicAuth") is None
+
+    def test_build_from_spec_missing_scheme_raises_error(self):
+        """Test that missing security scheme raises error."""
+        auth = AuthConfig()
+
+        security_schemes = {{
+            "ApiKeyAuth": {{"type": "apiKey", "name": "X-API-Key", "in": "header"}},
+        }}
+
+        security_requirements = [
+            {{"MissingScheme": []}},
+        ]
+
+        with pytest.raises(MissingSecuritySchemeError):
+            auth.build_from_spec(security_schemes, security_requirements)
+
+    def test_generate_pytest_auth_code(self):
+        """Test generating pytest authentication code."""
+        auth = AuthConfig()
+        auth.add_api_key("test_key", header_name="X-Api-Key", api_key="key123")
+
+        code = auth.generate_auth_code("test_key", "pytest")
+
+        assert "X-Api-Key" in code
+        assert "key123" in code
+
+    def test_generate_jest_auth_code(self):
+        """Test generating Jest authentication code."""
+        auth = AuthConfig()
+        auth.add_bearer("test_bearer", token="token123")
+
+        code = auth.generate_auth_code("test_bearer", "jest")
+
+        assert "Authorization" in code
+        assert "token123" in code
+
+    def test_generate_go_auth_code(self):
+        """Test generating Go authentication code."""
+        auth = AuthConfig()
+        auth.add_api_key("test_key", header_name="X-Api-Key")
+
+        code = auth.generate_auth_code("test_key", "go")
+
+        assert "X-Api-Key" in code
+
+    def test_generate_auth_code_unconfigured_scheme(self):
+        """Test generating auth code for unconfigured scheme returns empty."""
+        auth = AuthConfig()
+
+        code = auth.generate_auth_code("nonexistent", "pytest")
+
+        assert code == ""