diff --git a/.gitignore b/.gitignore
index 2a2b503..4ceafef 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,4 +30,12 @@ go.sum
 # OS generated files
 .DS_Store
 
+# builds
 openmcpauthproxy
+
+# test out files
+coverage.out
+coverage.html
+
+# IDE files
+.vscode
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..7fd2574
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,73 @@
+# Makefile for open-mcp-auth-proxy
+
+# Variables
+BINARY_NAME := openmcpauthproxy
+GO := go
+GOFMT := gofmt
+GOVET := go vet
+GOTEST := go test
+GOLINT := golangci-lint
+GOCOV := go tool cover
+BUILD_DIR := build
+
+# Source files
+SRC := $(shell find . -name "*.go" -not -path "./vendor/*")
+PKGS := $(shell go list ./... | grep -v /vendor/)
+
+# Set build options
+BUILD_OPTS := -v
+
+# Set test options
+TEST_OPTS := -v -race
+
+.PHONY: all build clean test fmt lint vet coverage help
+
+# Default target
+all: lint test build
+
+# Build the application
+build: 
+	@echo "Building $(BINARY_NAME)..."
+	@mkdir -p $(BUILD_DIR)
+	$(GO) build $(BUILD_OPTS) -o $(BUILD_DIR)/$(BINARY_NAME) ./cmd/proxy
+
+# Clean build artifacts
+clean:
+	@echo "Cleaning build artifacts..."
+	@rm -rf $(BUILD_DIR)
+	@rm -f coverage.out
+
+# Run tests
+test:
+	@echo "Running tests..."
+	$(GOTEST) $(TEST_OPTS) ./...
+
+# Run tests with coverage report
+coverage:
+	@echo "Running tests with coverage..."
+	@$(GOTEST) -coverprofile=coverage.out ./...
+	@$(GOCOV) -func=coverage.out
+	@$(GOCOV) -html=coverage.out -o coverage.html
+	@echo "Coverage report generated in coverage.html"
+
+# Run gofmt
+fmt:
+	@echo "Running gofmt..."
+	@$(GOFMT) -w -s $(SRC)
+
+# Run go vet
+vet:
+	@echo "Running go vet..."
+	@$(GOVET) ./...
+
+# Show help
+help:
+	@echo "Available targets:"
+	@echo "  all        : Run lint, test, and build"
+	@echo "  build      : Build the application"
+	@echo "  clean      : Clean build artifacts"
+	@echo "  test       : Run tests"
+	@echo "  coverage   : Run tests with coverage report"
+	@echo "  fmt        : Run gofmt"
+	@echo "  vet        : Run go vet"
+	@echo "  help       : Show this help message"
diff --git a/internal/authz/default_test.go b/internal/authz/default_test.go
new file mode 100644
index 0000000..f40030f
--- /dev/null
+++ b/internal/authz/default_test.go
@@ -0,0 +1,125 @@
+package authz
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/wso2/open-mcp-auth-proxy/internal/config"
+)
+
+func TestNewDefaultProvider(t *testing.T) {
+	cfg := &config.Config{}
+	provider := NewDefaultProvider(cfg)
+
+	if provider == nil {
+		t.Fatal("Expected non-nil provider")
+	}
+
+	// Ensure it implements the Provider interface
+	var _ Provider = provider
+}
+
+func TestDefaultProviderWellKnownHandler(t *testing.T) {
+	// Create a config with a custom well-known response
+	cfg := &config.Config{
+		Default: config.DefaultConfig{
+			Path: map[string]config.PathConfig{
+				"/.well-known/oauth-authorization-server": {
+					Response: &config.ResponseConfig{
+						Issuer:                        "https://test-issuer.com",
+						JwksURI:                       "https://test-issuer.com/jwks",
+						ResponseTypesSupported:        []string{"code"},
+						GrantTypesSupported:           []string{"authorization_code"},
+						CodeChallengeMethodsSupported: []string{"S256"},
+					},
+				},
+			},
+		},
+	}
+
+	provider := NewDefaultProvider(cfg)
+	handler := provider.WellKnownHandler()
+
+	// Create a test request
+	req := httptest.NewRequest("GET", "/.well-known/oauth-authorization-server", nil)
+	req.Host = "test-host.com"
+	req.Header.Set("X-Forwarded-Proto", "https")
+
+	// Create a response recorder
+	w := httptest.NewRecorder()
+
+	// Call the handler
+	handler(w, req)
+
+	// Check response status
+	if w.Code != http.StatusOK {
+		t.Errorf("Expected status OK, got %v", w.Code)
+	}
+
+	// Verify content type
+	contentType := w.Header().Get("Content-Type")
+	if contentType != "application/json" {
+		t.Errorf("Expected Content-Type: application/json, got %s", contentType)
+	}
+
+	// Decode and check the response body
+	var response map[string]interface{}
+	if err := json.NewDecoder(w.Body).Decode(&response); err != nil {
+		t.Fatalf("Failed to decode response JSON: %v", err)
+	}
+
+	// Check expected values
+	if response["issuer"] != "https://test-issuer.com" {
+		t.Errorf("Expected issuer=https://test-issuer.com, got %v", response["issuer"])
+	}
+	if response["jwks_uri"] != "https://test-issuer.com/jwks" {
+		t.Errorf("Expected jwks_uri=https://test-issuer.com/jwks, got %v", response["jwks_uri"])
+	}
+	if response["authorization_endpoint"] != "https://test-host.com/authorize" {
+		t.Errorf("Expected authorization_endpoint=https://test-host.com/authorize, got %v", response["authorization_endpoint"])
+	}
+}
+
+func TestDefaultProviderHandleOPTIONS(t *testing.T) {
+	provider := NewDefaultProvider(&config.Config{})
+	handler := provider.WellKnownHandler()
+
+	// Create OPTIONS request
+	req := httptest.NewRequest("OPTIONS", "/.well-known/oauth-authorization-server", nil)
+	w := httptest.NewRecorder()
+
+	// Call the handler
+	handler(w, req)
+
+	// Check response
+	if w.Code != http.StatusNoContent {
+		t.Errorf("Expected status NoContent for OPTIONS request, got %v", w.Code)
+	}
+
+	// Check CORS headers
+	if w.Header().Get("Access-Control-Allow-Origin") != "*" {
+		t.Errorf("Expected Access-Control-Allow-Origin: *, got %s", w.Header().Get("Access-Control-Allow-Origin"))
+	}
+	if w.Header().Get("Access-Control-Allow-Methods") != "GET, OPTIONS" {
+		t.Errorf("Expected Access-Control-Allow-Methods: GET, OPTIONS, got %s", w.Header().Get("Access-Control-Allow-Methods"))
+	}
+}
+
+func TestDefaultProviderInvalidMethod(t *testing.T) {
+	provider := NewDefaultProvider(&config.Config{})
+	handler := provider.WellKnownHandler()
+
+	// Create POST request (which should be rejected)
+	req := httptest.NewRequest("POST", "/.well-known/oauth-authorization-server", nil)
+	w := httptest.NewRecorder()
+
+	// Call the handler
+	handler(w, req)
+
+	// Check response
+	if w.Code != http.StatusMethodNotAllowed {
+		t.Errorf("Expected status MethodNotAllowed for POST request, got %v", w.Code)
+	}
+}
diff --git a/internal/config/config_test.go b/internal/config/config_test.go
new file mode 100644
index 0000000..20c0893
--- /dev/null
+++ b/internal/config/config_test.go
@@ -0,0 +1,196 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestLoadConfig(t *testing.T) {
+	// Create a temporary config file
+	tempDir := t.TempDir()
+	configPath := filepath.Join(tempDir, "test_config.yaml")
+
+	// Basic valid config
+	validConfig := `
+listen_port: 8080
+base_url: "http://localhost:8000"
+transport_mode: "sse"
+paths:
+  sse: "/sse"
+  messages: "/messages"
+cors:
+  allowed_origins:
+    - "http://localhost:5173"
+  allowed_methods:
+    - "GET"
+    - "POST"
+  allowed_headers:
+    - "Authorization"
+    - "Content-Type"
+  allow_credentials: true
+`
+	err := os.WriteFile(configPath, []byte(validConfig), 0644)
+	if err != nil {
+		t.Fatalf("Failed to create test config file: %v", err)
+	}
+
+	// Test loading the valid config
+	cfg, err := LoadConfig(configPath)
+	if err != nil {
+		t.Fatalf("Failed to load valid config: %v", err)
+	}
+
+	// Verify expected values from the config
+	if cfg.ListenPort != 8080 {
+		t.Errorf("Expected ListenPort=8080, got %d", cfg.ListenPort)
+	}
+	if cfg.BaseURL != "http://localhost:8000" {
+		t.Errorf("Expected BaseURL=http://localhost:8000, got %s", cfg.BaseURL)
+	}
+	if cfg.TransportMode != SSETransport {
+		t.Errorf("Expected TransportMode=sse, got %s", cfg.TransportMode)
+	}
+	if cfg.Paths.SSE != "/sse" {
+		t.Errorf("Expected Paths.SSE=/sse, got %s", cfg.Paths.SSE)
+	}
+	if cfg.Paths.Messages != "/messages" {
+		t.Errorf("Expected Paths.Messages=/messages, got %s", cfg.Paths.Messages)
+	}
+
+	// Test default values
+	if cfg.TimeoutSeconds != 15 {
+		t.Errorf("Expected default TimeoutSeconds=15, got %d", cfg.TimeoutSeconds)
+	}
+	if cfg.Port != 8000 {
+		t.Errorf("Expected default Port=8000, got %d", cfg.Port)
+	}
+}
+
+func TestValidate(t *testing.T) {
+	tests := []struct {
+		name        string
+		config      Config
+		expectError bool
+	}{
+		{
+			name: "Valid SSE config",
+			config: Config{
+				TransportMode: SSETransport,
+				Paths: PathsConfig{
+					SSE:      "/sse",
+					Messages: "/messages",
+				},
+				BaseURL: "http://localhost:8000",
+			},
+			expectError: false,
+		},
+		{
+			name: "Valid stdio config",
+			config: Config{
+				TransportMode: StdioTransport,
+				Stdio: StdioConfig{
+					Enabled:     true,
+					UserCommand: "some-command",
+				},
+			},
+			expectError: false,
+		},
+		{
+			name: "Invalid stdio config - not enabled",
+			config: Config{
+				TransportMode: StdioTransport,
+				Stdio: StdioConfig{
+					Enabled:     false,
+					UserCommand: "some-command",
+				},
+			},
+			expectError: true,
+		},
+		{
+			name: "Invalid stdio config - no command",
+			config: Config{
+				TransportMode: StdioTransport,
+				Stdio: StdioConfig{
+					Enabled:     true,
+					UserCommand: "",
+				},
+			},
+			expectError: true,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			err := tc.config.Validate()
+			if tc.expectError && err == nil {
+				t.Errorf("Expected validation error but got none")
+			}
+			if !tc.expectError && err != nil {
+				t.Errorf("Expected no validation error but got: %v", err)
+			}
+		})
+	}
+}
+
+func TestGetMCPPaths(t *testing.T) {
+	cfg := Config{
+		Paths: PathsConfig{
+			SSE:      "/custom-sse",
+			Messages: "/custom-messages",
+		},
+	}
+
+	paths := cfg.GetMCPPaths()
+	if len(paths) != 2 {
+		t.Errorf("Expected 2 MCP paths, got %d", len(paths))
+	}
+	if paths[0] != "/custom-sse" {
+		t.Errorf("Expected first path=/custom-sse, got %s", paths[0])
+	}
+	if paths[1] != "/custom-messages" {
+		t.Errorf("Expected second path=/custom-messages, got %s", paths[1])
+	}
+}
+
+func TestBuildExecCommand(t *testing.T) {
+	tests := []struct {
+		name           string
+		config         Config
+		expectedResult string
+	}{
+		{
+			name: "Valid command",
+			config: Config{
+				Stdio: StdioConfig{
+					UserCommand: "test-command",
+				},
+				Port:    8080,
+				BaseURL: "http://example.com",
+				Paths: PathsConfig{
+					SSE:      "/sse-path",
+					Messages: "/msgs",
+				},
+			},
+			expectedResult: `npx -y supergateway --stdio "test-command" --port 8080 --baseUrl http://example.com --ssePath /sse-path --messagePath /msgs`,
+		},
+		{
+			name: "Empty command",
+			config: Config{
+				Stdio: StdioConfig{
+					UserCommand: "",
+				},
+			},
+			expectedResult: "",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			result := tc.config.BuildExecCommand()
+			if result != tc.expectedResult {
+				t.Errorf("Expected command=%s, got %s", tc.expectedResult, result)
+			}
+		})
+	}
+}
diff --git a/internal/proxy/modifier_test.go b/internal/proxy/modifier_test.go
new file mode 100644
index 0000000..3d2fd44
--- /dev/null
+++ b/internal/proxy/modifier_test.go
@@ -0,0 +1,147 @@
+package proxy
+
+import (
+	"net/http"
+	"net/url"
+	"strings"
+	"testing"
+
+	"github.com/wso2/open-mcp-auth-proxy/internal/config"
+)
+
+func TestAuthorizationModifier(t *testing.T) {
+	cfg := &config.Config{
+		Default: config.DefaultConfig{
+			Path: map[string]config.PathConfig{
+				"/authorize": {
+					AddQueryParams: []config.ParamConfig{
+						{Name: "client_id", Value: "test-client-id"},
+						{Name: "scope", Value: "openid"},
+					},
+				},
+			},
+		},
+	}
+
+	modifier := &AuthorizationModifier{Config: cfg}
+
+	// Create a test request
+	req, err := http.NewRequest("GET", "/authorize?response_type=code", nil)
+	if err != nil {
+		t.Fatalf("Failed to create request: %v", err)
+	}
+
+	// Modify the request
+	modifiedReq, err := modifier.ModifyRequest(req)
+	if err != nil {
+		t.Fatalf("ModifyRequest failed: %v", err)
+	}
+
+	// Check that the query parameters were added
+	query := modifiedReq.URL.Query()
+	if query.Get("client_id") != "test-client-id" {
+		t.Errorf("Expected client_id=test-client-id, got %s", query.Get("client_id"))
+	}
+	if query.Get("scope") != "openid" {
+		t.Errorf("Expected scope=openid, got %s", query.Get("scope"))
+	}
+	if query.Get("response_type") != "code" {
+		t.Errorf("Expected response_type=code, got %s", query.Get("response_type"))
+	}
+}
+
+func TestTokenModifier(t *testing.T) {
+	cfg := &config.Config{
+		Default: config.DefaultConfig{
+			Path: map[string]config.PathConfig{
+				"/token": {
+					AddBodyParams: []config.ParamConfig{
+						{Name: "audience", Value: "test-audience"},
+					},
+				},
+			},
+		},
+	}
+
+	modifier := &TokenModifier{Config: cfg}
+
+	// Create a test request with form data
+	form := url.Values{}
+
+	req, err := http.NewRequest("POST", "/token", strings.NewReader(form.Encode()))
+	if err != nil {
+		t.Fatalf("Failed to create request: %v", err)
+	}
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+
+	// Modify the request
+	modifiedReq, err := modifier.ModifyRequest(req)
+	if err != nil {
+		t.Fatalf("ModifyRequest failed: %v", err)
+	}
+
+	body := make([]byte, 1024)
+	n, err := modifiedReq.Body.Read(body)
+	if err != nil && err.Error() != "EOF" {
+		t.Fatalf("Failed to read body: %v", err)
+	}
+	bodyStr := string(body[:n])
+
+	// Parse the form data from the modified request
+	if err := modifiedReq.ParseForm(); err != nil {
+		t.Fatalf("Failed to parse form data: %v", err)
+	}
+
+	// Check that the body parameters were added
+	if !strings.Contains(bodyStr, "audience") {
+		t.Errorf("Expected body to contain audience, got %s", bodyStr)
+	}
+}
+
+func TestRegisterModifier(t *testing.T) {
+	cfg := &config.Config{
+		Default: config.DefaultConfig{
+			Path: map[string]config.PathConfig{
+				"/register": {
+					AddBodyParams: []config.ParamConfig{
+						{Name: "client_name", Value: "test-client"},
+					},
+				},
+			},
+		},
+	}
+
+	modifier := &RegisterModifier{Config: cfg}
+
+	// Create a test request with JSON data
+	jsonBody := `{"redirect_uris":["https://example.com/callback"]}`
+	req, err := http.NewRequest("POST", "/register", strings.NewReader(jsonBody))
+	if err != nil {
+		t.Fatalf("Failed to create request: %v", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+
+	// Modify the request
+	modifiedReq, err := modifier.ModifyRequest(req)
+	if err != nil {
+		t.Fatalf("ModifyRequest failed: %v", err)
+	}
+
+	// Read the body and check that it still contains the original data
+	// This test would need to be enhanced with a proper JSON parsing to verify
+	// the added parameters
+	body := make([]byte, 1024)
+	n, err := modifiedReq.Body.Read(body)
+	if err != nil && err.Error() != "EOF" {
+		t.Fatalf("Failed to read body: %v", err)
+	}
+	bodyStr := string(body[:n])
+
+	// Simple check to see if the modified body contains the expected fields
+	if !strings.Contains(bodyStr, "client_name") {
+		t.Errorf("Expected body to contain client_name, got %s", bodyStr)
+	}
+	if !strings.Contains(bodyStr, "redirect_uris") {
+		t.Errorf("Expected body to contain redirect_uris, got %s", bodyStr)
+	}
+}
diff --git a/internal/util/jwks_test.go b/internal/util/jwks_test.go
new file mode 100644
index 0000000..3b00c68
--- /dev/null
+++ b/internal/util/jwks_test.go
@@ -0,0 +1,143 @@
+package util
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"encoding/base64"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/golang-jwt/jwt/v4"
+)
+
+func TestValidateJWT(t *testing.T) {
+	// Initialize the test JWKS data
+	initTestJWKS(t)
+
+	// Test cases
+	tests := []struct {
+		name        string
+		authHeader  string
+		expectError bool
+	}{
+		{
+			name:        "Valid JWT token",
+			authHeader:  "Bearer " + createValidJWT(t),
+			expectError: false,
+		},
+		{
+			name:        "No auth header",
+			authHeader:  "",
+			expectError: true,
+		},
+		{
+			name:        "Invalid auth header format",
+			authHeader:  "InvalidFormat",
+			expectError: true,
+		},
+		{
+			name:        "Invalid JWT token",
+			authHeader:  "Bearer invalid.jwt.token",
+			expectError: true,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			err := ValidateJWT(tc.authHeader)
+			if tc.expectError && err == nil {
+				t.Errorf("Expected error but got none")
+			}
+			if !tc.expectError && err != nil {
+				t.Errorf("Expected no error but got: %v", err)
+			}
+		})
+	}
+}
+
+func TestFetchJWKS(t *testing.T) {
+	// Create a mock JWKS server
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Generate a test RSA key
+		privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
+		if err != nil {
+			t.Fatalf("Failed to generate RSA key: %v", err)
+		}
+
+		// Create JWKS response
+		jwks := map[string]interface{}{
+			"keys": []map[string]interface{}{
+				{
+					"kty": "RSA",
+					"kid": "test-key-id",
+					"n":   base64.RawURLEncoding.EncodeToString(privateKey.N.Bytes()),
+					"e":   base64.RawURLEncoding.EncodeToString([]byte{1, 0, 1}), // Default exponent 65537
+				},
+			},
+		}
+
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(jwks)
+	}))
+	defer server.Close()
+
+	// Test fetching JWKS
+	err := FetchJWKS(server.URL)
+	if err != nil {
+		t.Fatalf("FetchJWKS failed: %v", err)
+	}
+
+	// Check that keys were stored
+	if len(publicKeys) == 0 {
+		t.Errorf("Expected publicKeys to be populated")
+	}
+}
+
+// Helper function to initialize test JWKS data
+func initTestJWKS(t *testing.T) {
+	// Create a test RSA key pair
+	privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		t.Fatalf("Failed to generate RSA key: %v", err)
+	}
+
+	// Initialize the publicKeys map
+	publicKeys = map[string]*rsa.PublicKey{
+		"test-key-id": &privateKey.PublicKey,
+	}
+}
+
+// Helper function to create a valid JWT token for testing
+func createValidJWT(t *testing.T) string {
+	// Create a test RSA key pair
+	privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
+	if err != nil {
+		t.Fatalf("Failed to generate RSA key: %v", err)
+	}
+
+	// Ensure the test key is in the publicKeys map
+	if publicKeys == nil {
+		publicKeys = map[string]*rsa.PublicKey{}
+	}
+	publicKeys["test-key-id"] = &privateKey.PublicKey
+
+	// Create token
+	token := jwt.NewWithClaims(jwt.SigningMethodRS256, jwt.MapClaims{
+		"sub":  "1234567890",
+		"name": "Test User",
+		"iat":  time.Now().Unix(),
+		"exp":  time.Now().Add(time.Hour).Unix(),
+	})
+	token.Header["kid"] = "test-key-id"
+
+	// Sign the token
+	tokenString, err := token.SignedString(privateKey)
+	if err != nil {
+		t.Fatalf("Failed to sign token: %v", err)
+	}
+
+	return tokenString
+}