diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a90900a..6a140df 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,7 +19,7 @@ jobs:
           bundler-cache: true
 
       - name: Lint code for consistent style
-        run: bin/rubocop -f github
+        run: bundle exec rubocop -f github
 
   test:
     runs-on: ubuntu-latest
@@ -44,10 +44,7 @@ jobs:
           bundler-cache: true
 
       - name: Run tests
-        env:
-          RAILS_ENV: test
-          # REDIS_URL: redis://localhost:6379/0
-        run: bin/rails db:test:prepare test
+        run: bundle exec rspec
 
       - name: Keep screenshots from failed system tests
         uses: actions/upload-artifact@v4
diff --git a/.gitignore b/.gitignore
index 0439d1f..dcd2884 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,10 +2,5 @@
 /doc/
 /log/*.log
 /pkg/
-/tmp/
-/test/dummy/db/*.sqlite3
-/test/dummy/db/*.sqlite3-*
-/test/dummy/log/*.log
-/test/dummy/storage/
-/test/dummy/tmp/
+/spec/internal/tmp/
 Claude.md
diff --git a/.rspec b/.rspec
new file mode 100644
index 0000000..f8f74f2
--- /dev/null
+++ b/.rspec
@@ -0,0 +1,3 @@
+--color
+--require spec_helper
+--format documentation
\ No newline at end of file
diff --git a/Gemfile.lock b/Gemfile.lock
index a4fbf1d..35da460 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,8 +1,8 @@
 PATH
   remote: .
   specs:
-    fileboost (0.1.0)
-      rails (>= 8.0.2.1)
+    fileboost (0.1.1)
+      activestorage (>= 6.0)
 
 GEM
   remote: https://rubygems.org/
@@ -83,10 +83,15 @@ GEM
     benchmark (0.4.1)
     bigdecimal (3.2.3)
     builder (3.3.0)
+    combustion (1.5.0)
+      activesupport (>= 3.0.0)
+      railties (>= 3.0.0)
+      thor (>= 0.14.6)
     concurrent-ruby (1.3.5)
     connection_pool (2.5.4)
     crass (1.0.6)
     date (3.4.1)
+    diff-lcs (1.6.2)
     drb (2.2.3)
     erb (5.0.2)
     erubi (1.13.1)
@@ -126,6 +131,8 @@ GEM
     nio4r (2.7.4)
     nokogiri (1.18.9-arm64-darwin)
       racc (~> 1.4)
+    nokogiri (1.18.9-x86_64-linux-gnu)
+      racc (~> 1.4)
     parallel (1.27.0)
     parser (3.3.9.0)
       ast (~> 2.4.1)
@@ -189,6 +196,27 @@ GEM
     regexp_parser (2.11.2)
     reline (0.6.2)
       io-console (~> 0.5)
+    rspec (3.13.1)
+      rspec-core (~> 3.13.0)
+      rspec-expectations (~> 3.13.0)
+      rspec-mocks (~> 3.13.0)
+    rspec-core (3.13.5)
+      rspec-support (~> 3.13.0)
+    rspec-expectations (3.13.5)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-mocks (3.13.5)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-rails (6.1.5)
+      actionpack (>= 6.1)
+      activesupport (>= 6.1)
+      railties (>= 6.1)
+      rspec-core (~> 3.13)
+      rspec-expectations (~> 3.13)
+      rspec-mocks (~> 3.13)
+      rspec-support (~> 3.13)
+    rspec-support (3.13.5)
     rubocop (1.80.2)
       json (~> 2.3)
       language_server-protocol (~> 3.17.0.2)
@@ -220,6 +248,7 @@ GEM
     ruby-progressbar (1.13.0)
     securerandom (0.4.1)
     sqlite3 (2.7.3-arm64-darwin)
+    sqlite3 (2.7.3-x86_64-linux-gnu)
     stringio (3.1.7)
     thor (1.4.0)
     timeout (0.4.3)
@@ -238,13 +267,20 @@ GEM
 
 PLATFORMS
   arm64-darwin
+  x86_64-linux
 
 DEPENDENCIES
+  bundler (~> 2)
+  combustion (~> 1)
   fileboost!
   propshaft
   puma
+  rails (~> 8.0.0)
+  rake (~> 13.0)
+  rspec (~> 3.0)
+  rspec-rails (~> 6.0)
   rubocop-rails-omakase
-  sqlite3
+  sqlite3 (~> 2.0, >= 0)
 
 BUNDLED WITH
    2.7.1
diff --git a/Rakefile b/Rakefile
index e7793b5..dbd59ee 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,8 +1,7 @@
 require "bundler/setup"
+require "bundler/gem_tasks"
+require "rspec/core/rake_task"
 
-APP_RAKEFILE = File.expand_path("test/dummy/Rakefile", __dir__)
-load "rails/tasks/engine.rake"
-
-load "rails/tasks/statistics.rake"
+RSpec::Core::RakeTask.new(:spec)
 
-require "bundler/gem_tasks"
+task default: :spec
diff --git a/fileboost.gemspec b/fileboost.gemspec
index 4db3941..72f01d9 100644
--- a/fileboost.gemspec
+++ b/fileboost.gemspec
@@ -22,8 +22,11 @@ Gem::Specification.new do |spec|
 
   spec.add_runtime_dependency "activestorage", ">= 6.0"
 
-  spec.add_development_dependency "bundler", "~> 1.15"
-  spec.add_development_dependency "combustion", "~> 1.1"
+  spec.add_development_dependency "bundler", "~> 2"
+  spec.add_development_dependency "combustion", "~> 1"
   spec.add_development_dependency "rake", "~> 13.0"
   spec.add_development_dependency "rails", "~> 8.0.0"
+  spec.add_development_dependency "rspec", "~> 3.0"
+  spec.add_development_dependency "rspec-rails", "~> 6.0"
+  spec.add_development_dependency "sqlite3", "~> 2.0"
 end
diff --git a/lib/fileboost/config.rb b/lib/fileboost/config.rb
index e93cdbe..e76dce4 100644
--- a/lib/fileboost/config.rb
+++ b/lib/fileboost/config.rb
@@ -11,7 +11,7 @@ def initialize
     end
 
     def valid?
-      project_id.present? && token.present?
+      !project_id.empty? && !token.empty?
     end
 
     def base_url
@@ -26,4 +26,4 @@ def self.config
   def self.configure
     yield(config) if block_given?
   end
-end
\ No newline at end of file
+end
diff --git a/lib/fileboost/engine.rb b/lib/fileboost/engine.rb
index c68d898..32adc79 100644
--- a/lib/fileboost/engine.rb
+++ b/lib/fileboost/engine.rb
@@ -7,11 +7,5 @@ class Engine < ::Rails::Engine
         include Fileboost::Helpers
       end
     end
-
-    initializer "fileboost.active_storage" do
-      ActiveSupport.on_load :active_storage_blob do
-        # Extend ActiveStorage::Blob with fileboost-specific methods if needed
-      end
-    end
   end
 end
diff --git a/lib/fileboost/error_handler.rb b/lib/fileboost/error_handler.rb
index 26b83d5..1354769 100644
--- a/lib/fileboost/error_handler.rb
+++ b/lib/fileboost/error_handler.rb
@@ -1,57 +1,7 @@
 module Fileboost
-  class ErrorHandler
-    class << self
-      def handle_with_fallback(error_context, &block)
-        begin
-          yield
-        rescue StandardError => e
-          log_error(error_context, e)
-          
-          if Fileboost.config.fallback_to_rails
-            yield_fallback if block_given?
-          else
-            nil
-          end
-        end
-      end
-
-      def handle_gracefully(error_context, default_value = nil, &block)
-        begin
-          yield
-        rescue StandardError => e
-          log_error(error_context, e)
-          default_value
-        end
-      end
-
-      private
-
-      def log_error(context, error)
-        return unless defined?(Rails) && Rails.logger
-
-        Rails.logger.warn(
-          "[Fileboost] Error in #{context}: #{error.class}: #{error.message}"
-        )
-        
-        # Log backtrace in development for debugging
-        if Rails.env.development?
-          Rails.logger.debug(
-            "[Fileboost] Backtrace:\n#{error.backtrace.take(5).join("\n")}"
-          )
-        end
-      end
-
-      def yield_fallback
-        # This would be implemented by the calling code
-        # The pattern is to pass a fallback block when needed
-        nil
-      end
-    end
-  end
-
   # Specific exception classes for better error handling
   class ConfigurationError < StandardError; end
   class SignatureGenerationError < StandardError; end
   class UrlBuildError < StandardError; end
   class AssetPathExtractionError < StandardError; end
-end
\ No newline at end of file
+end
diff --git a/lib/fileboost/helpers.rb b/lib/fileboost/helpers.rb
index e7b387b..50909cc 100644
--- a/lib/fileboost/helpers.rb
+++ b/lib/fileboost/helpers.rb
@@ -18,9 +18,6 @@ def fileboost_image_tag(asset, **options)
       # Generate the optimized URL
       optimized_url = fileboost_url_for(asset, resize: resize_options)
 
-      # Return empty string if no URL could be generated
-      return "" if optimized_url.blank?
-
       # Use the optimized URL with Rails image_tag for consistency
       image_tag(optimized_url, **options)
     end
@@ -36,16 +33,10 @@ def fileboost_image_tag(asset, **options)
     #   fileboost_url_for(user.avatar.blob, resize: { w: 1200, h: 400, q: 85 })
     def fileboost_url_for(asset, **options)
       # Validate that asset is an ActiveStorage object
-      unless valid_activestorage_asset?(asset)
-        Rails.logger.error("[Fileboost] Invalid asset type #{asset.class}. Only ActiveStorage objects are supported.") if defined?(Rails)
-        return nil
-      end
+      raise ArgumentError, "Invalid asset type #{asset.class}. Only ActiveStorage objects are supported." unless valid_activestorage_asset?(asset)
 
       # Validate configuration
-      unless Fileboost.config.valid?
-        log_configuration_warning
-        return nil
-      end
+      raise Fileboost::ConfigurationError, "Invalid Fileboost configuration" unless Fileboost.config.valid?
 
       # Build the optimized URL
       Fileboost::UrlBuilder.build_url(asset, **options)
@@ -71,10 +62,13 @@ def fileboost_responsive_urls(asset, sizes, **base_options)
       sizes.each do |size_config|
         suffix = size_config[:suffix] || size_config["suffix"]
         size_options = size_config.except(:suffix, "suffix")
-        combined_options = base_options.merge(size_options)
+
+        # Merge size options into base resize options
+        merged_resize_options = (base_options[:resize] || {}).merge(size_options)
+        combined_options = base_options.merge(resize: merged_resize_options)
 
         url = fileboost_url_for(asset, **combined_options)
-        urls[suffix] = url if url.present?
+        urls[suffix] = url if !url.nil? && !url.empty?
       end
 
       urls
@@ -91,17 +85,5 @@ def valid_activestorage_asset?(asset)
 
       false
     end
-
-    # Log configuration warnings
-    def log_configuration_warning
-      missing_configs = []
-      missing_configs << "project_id" if Fileboost.config.project_id.blank?
-      missing_configs << "token" if Fileboost.config.token.blank?
-
-      Rails.logger.warn(
-        "[Fileboost] Configuration incomplete. Missing: #{missing_configs.join(', ')}. " \
-        "Set FILEBOOST_PROJECT_ID and FILEBOOST_TOKEN environment variables or configure them in your initializer."
-      ) if defined?(Rails)
-    end
   end
 end
diff --git a/lib/fileboost/signature_generator.rb b/lib/fileboost/signature_generator.rb
index 8660ed2..d1eb031 100644
--- a/lib/fileboost/signature_generator.rb
+++ b/lib/fileboost/signature_generator.rb
@@ -3,42 +3,17 @@
 
 module Fileboost
   class SignatureGenerator
-    def self.generate(project_id:, asset_path:, params: {})
-      return nil unless project_id.present? && asset_path.present? && Fileboost.config.token.present?
-
+    def self.generate(asset_path:, params: {})
       # Sort parameters for consistent signature generation
       sorted_params = params.sort.to_h
       query_string = sorted_params.map { |k, v| "#{k}=#{v}" }.join("&")
 
       # Create the signing string: project_id:asset_path:sorted_query_params
-      signing_string = [project_id, asset_path, query_string].join(":")
-      Rails.logger.debug("signature payload #{project_id}, #{asset_path}, #{query_string}, #{Fileboost.config.token}")
+      signing_string = [ Fileboost.config.project_id, asset_path, query_string ].join(":")
       # Generate HMAC-SHA256 signature for secure authentication with Fileboost.dev
       digest = OpenSSL::HMAC.digest("SHA256", Fileboost.config.token, signing_string)
       # Use URL-safe base64 encoding and remove padding for maximum URL compatibility
       Base64.urlsafe_encode64(digest, padding: false)
-    rescue StandardError => e
-      if defined?(Rails) && Rails.env.development?
-        raise e
-      else
-        Rails.logger.warn("[Fileboost] Failed to generate signature: #{e.message}") if defined?(Rails)
-        nil
-      end
-    end
-
-    def self.verify_signature(project_id:, asset_path:, params: {}, signature:)
-      expected_signature = generate(project_id: project_id, asset_path: asset_path, params: params)
-      return false if expected_signature.nil? || signature.nil?
-
-      # Use secure comparison to prevent timing attacks
-      ActiveSupport::SecurityUtils.secure_compare(signature, expected_signature)
-    rescue StandardError => e
-      if defined?(Rails) && Rails.env.development?
-        raise e
-      else
-        Rails.logger.warn("[Fileboost] Failed to verify signature: #{e.message}") if defined?(Rails)
-        false
-      end
     end
   end
 end
diff --git a/lib/fileboost/url_builder.rb b/lib/fileboost/url_builder.rb
index 1a7eb68..188e4ef 100644
--- a/lib/fileboost/url_builder.rb
+++ b/lib/fileboost/url_builder.rb
@@ -31,44 +31,36 @@ class UrlBuilder
     RESIZE_PARAMS = %w[w width h height q quality f format b blur br brightness c contrast r rotation fit].freeze
 
     def self.build_url(asset, **options)
-      return nil unless Fileboost.config.valid?
-      
+      raise ConfigurationError, "Invalid configuration" unless Fileboost.config.valid?
+
       asset_path = extract_asset_path(asset)
-      return nil unless asset_path.present?
+      raise AssetPathExtractionError, "Unable to extract asset path" unless !asset_path.nil? && !asset_path.empty?
 
       project_id = Fileboost.config.project_id
       base_url = Fileboost.config.base_url
-      
+
       # Build the full asset URL path for Fileboost.dev service
       full_path = "/#{project_id}#{asset_path}"
-      
+
       # Extract and normalize transformation parameters
       transformation_params = extract_transformation_params(options)
-      
+
       # Generate HMAC signature for secure authentication
       signature = Fileboost::SignatureGenerator.generate(
-        project_id: project_id,
         asset_path: asset_path,
         params: transformation_params
       )
-      
-      return nil unless signature
-      
+
+      raise SignatureGenerationError, "Failed to generate signature" unless signature
+
       # Add signature to parameters
       all_params = transformation_params.merge("sig" => signature)
-      
+
       # Build final URL
       uri = URI.join(base_url, full_path)
       uri.query = URI.encode_www_form(all_params) unless all_params.empty?
-      
+
       uri.to_s
-    rescue StandardError => e
-      if defined?(Rails) && Rails.env.development?
-        raise e
-      else
-        Rails.logger.warn("[Fileboost] Failed to build URL: #{e.message}") if defined?(Rails)
-        nil
-      end
     end
 
     private
@@ -78,57 +70,48 @@ def self.extract_asset_path(asset)
       when ActiveStorage::Blob
         # ActiveStorage Blob
         Rails.application.routes.url_helpers.rails_blob_path(asset, only_path: true)
-        
+
       when ActiveStorage::Attached
         # ActiveStorage Attachment (has_one_attached, has_many_attached)
-        if asset.respond_to?(:blob) && asset.blob.present?
+        if asset.respond_to?(:blob) && !asset.blob.nil?
           Rails.application.routes.url_helpers.rails_blob_path(asset.blob, only_path: true)
         else
-          Rails.logger.warn("[Fileboost] ActiveStorage attachment has no blob") if defined?(Rails)
-          nil
+          raise AssetPathExtractionError, "ActiveStorage attachment has no blob"
         end
-        
+
       when ActiveStorage::VariantWithRecord
         # ActiveStorage Variant - use blob URL to avoid triggering variant generation
         Rails.application.routes.url_helpers.rails_blob_path(asset.blob, only_path: true)
-        
+
       else
         # Only ActiveStorage objects are supported
-        Rails.logger.warn("[Fileboost] Unsupported asset type: #{asset.class}. Only ActiveStorage objects are supported.") if defined?(Rails)
-        nil
-      end
-    rescue StandardError => e
-      if defined?(Rails) && Rails.env.development?
-        raise e
-      else
-        Rails.logger.warn("[Fileboost] Failed to extract asset path: #{e.message}") if defined?(Rails)
-        nil
+        raise AssetPathExtractionError, "Unsupported asset type: #{asset.class}. Only ActiveStorage objects are supported."
       end
     end
 
     def self.extract_transformation_params(options)
       params = {}
-      
+
       # Only handle nested resize parameter
       if options[:resize].is_a?(Hash)
         resize_options = options[:resize]
         resize_options.each do |key, value|
           key_str = key.to_s
-          
+
           # Only process valid resize parameters
           next unless RESIZE_PARAMS.include?(key_str)
-          
+
           # Use alias if available
           param_key = PARAM_ALIASES[key_str] || key_str
-          
+
           # Convert value to string and validate
           param_value = normalize_param_value(param_key, value)
-          next if param_value.blank?
-          
+          next if param_value.nil? || param_value.empty?
+
           params[param_key] = param_value
         end
       end
-      
+
       params
     end
 
@@ -152,4 +135,4 @@ def self.normalize_param_value(key, value)
       end
     end
   end
-end
\ No newline at end of file
+end
diff --git a/lib/generators/fileboost/install_generator.rb b/lib/generators/fileboost/install_generator.rb
index 61092f9..eea7c4b 100644
--- a/lib/generators/fileboost/install_generator.rb
+++ b/lib/generators/fileboost/install_generator.rb
@@ -4,7 +4,7 @@ module Fileboost
   module Generators
     class InstallGenerator < Rails::Generators::Base
       desc "Create Fileboost initializer file"
-      
+
       def self.source_root
         @source_root ||= File.expand_path("templates", __dir__)
       end
@@ -24,4 +24,4 @@ def readme(path)
       end
     end
   end
-end
\ No newline at end of file
+end
diff --git a/spec/fileboost/config_spec.rb b/spec/fileboost/config_spec.rb
new file mode 100644
index 0000000..2d262f0
--- /dev/null
+++ b/spec/fileboost/config_spec.rb
@@ -0,0 +1,51 @@
+require "spec_helper"
+
+RSpec.describe Fileboost::Config do
+  describe "#initialize" do
+    it "loads configuration from environment variables" do
+      ENV["FILEBOOST_PROJECT_ID"] = "test_project"
+      ENV["FILEBOOST_TOKEN"] = "test_token"
+
+      config = Fileboost::Config.new
+
+      expect(config.project_id).to eq("test_project")
+      expect(config.token).to eq("test_token")
+
+      ENV.delete("FILEBOOST_PROJECT_ID")
+      ENV.delete("FILEBOOST_TOKEN")
+    end
+  end
+
+  describe "#valid?" do
+    it "returns true when both project_id and token are present" do
+      config = Fileboost::Config.new
+      config.project_id = "test_project"
+      config.token = "test_token"
+
+      expect(config).to be_valid
+    end
+
+    it "returns false when project_id is missing" do
+      config = Fileboost::Config.new
+      config.project_id = ""
+      config.token = "test_token"
+
+      expect(config).not_to be_valid
+    end
+
+    it "returns false when token is missing" do
+      config = Fileboost::Config.new
+      config.project_id = "test_project"
+      config.token = ""
+
+      expect(config).not_to be_valid
+    end
+  end
+
+  describe "#base_url" do
+    it "returns the hardcoded CDN domain" do
+      config = Fileboost::Config.new
+      expect(config.base_url).to eq("https://cdn.fileboost.dev")
+    end
+  end
+end
diff --git a/spec/fileboost/helpers_spec.rb b/spec/fileboost/helpers_spec.rb
new file mode 100644
index 0000000..d168002
--- /dev/null
+++ b/spec/fileboost/helpers_spec.rb
@@ -0,0 +1,99 @@
+require "spec_helper"
+
+RSpec.describe Fileboost::Helpers do
+  include Fileboost::Helpers
+
+  let(:user) { User.create!(name: "Test User") }
+  let(:blob) do
+    ActiveStorage::Blob.create_and_upload!(
+      io: StringIO.new("fake image data"),
+      filename: "test.jpg",
+      content_type: "image/jpeg"
+    )
+  end
+
+  before do
+    Fileboost.configure do |config|
+      config.project_id = "test_project"
+      config.token = "test_token"
+    end
+  end
+
+  describe "#fileboost_url_for" do
+    it "generates URL for ActiveStorage::Blob" do
+      url = fileboost_url_for(blob, resize: { w: 300 })
+
+      expect(url).to include("https://cdn.fileboost.dev")
+      expect(url).to include("w=300")
+      expect(url).to include("sig=")
+    end
+
+    it "generates URL for ActiveStorage attachment" do
+      user.avatar.attach(blob)
+
+      url = fileboost_url_for(user.avatar, resize: { w: 300 })
+
+      expect(url).to include("https://cdn.fileboost.dev")
+      expect(url).to include("w=300")
+    end
+
+    it "raises ArgumentError for invalid asset type" do
+      expect {
+        fileboost_url_for("invalid", resize: { w: 300 })
+      }.to raise_error(ArgumentError, /Invalid asset type/)
+    end
+
+    it "raises ConfigurationError for invalid configuration" do
+      Fileboost.config.project_id = ""
+
+      expect {
+        fileboost_url_for(blob)
+      }.to raise_error(Fileboost::ConfigurationError)
+    end
+  end
+
+  describe "#fileboost_image_tag" do
+    it "generates image tag with optimized URL" do
+      allow(self).to receive(:image_tag).and_return('<img src="optimized_url" alt="test">')
+
+      result = fileboost_image_tag(blob, resize: { w: 300 }, alt: "test")
+
+      expect(result).to eq('<img src="optimized_url" alt="test">')
+    end
+  end
+
+  describe "#fileboost_responsive_urls" do
+    it "generates multiple URLs for responsive images" do
+      sizes = [
+        { width: 400, suffix: "sm" },
+        { width: 800, suffix: "md" },
+        { width: 1200, suffix: "lg" }
+      ]
+
+      urls = fileboost_responsive_urls(blob, sizes, resize: { quality: 85 })
+
+      expect(urls).to have_key("sm")
+      expect(urls).to have_key("md")
+      expect(urls).to have_key("lg")
+      expect(urls["sm"]).to include("w=400")
+      expect(urls["md"]).to include("w=800")
+      expect(urls["lg"]).to include("w=1200")
+    end
+  end
+
+  describe "#valid_activestorage_asset?" do
+    it "returns true for ActiveStorage::Blob" do
+      expect(send(:valid_activestorage_asset?, blob)).to be true
+    end
+
+    it "returns true for ActiveStorage::Attached" do
+      user.avatar.attach(blob)
+      expect(send(:valid_activestorage_asset?, user.avatar)).to be true
+    end
+
+    it "returns false for invalid asset types" do
+      expect(send(:valid_activestorage_asset?, "string")).to be false
+      expect(send(:valid_activestorage_asset?, 123)).to be false
+    end
+  end
+end
diff --git a/spec/fileboost/signature_generator_spec.rb b/spec/fileboost/signature_generator_spec.rb
new file mode 100644
index 0000000..4265262
--- /dev/null
+++ b/spec/fileboost/signature_generator_spec.rb
@@ -0,0 +1,66 @@
+require "spec_helper"
+
+RSpec.describe Fileboost::SignatureGenerator do
+  before do
+    Fileboost.configure do |config|
+      config.project_id = "test_project"
+      config.token = "test_token"
+    end
+  end
+
+  describe ".generate" do
+    it "generates a signature for valid parameters" do
+      signature = Fileboost::SignatureGenerator.generate(
+        asset_path: "/test/path.jpg",
+        params: { "w" => "300", "h" => "200" }
+      )
+
+      expect(signature).to be_a(String)
+      expect(signature).not_to be_empty
+    end
+
+    it "generates consistent signatures for same inputs" do
+      params = { "w" => "300", "h" => "200" }
+
+      signature1 = Fileboost::SignatureGenerator.generate(
+        asset_path: "/test/path.jpg",
+        params: params
+      )
+
+      signature2 = Fileboost::SignatureGenerator.generate(
+        asset_path: "/test/path.jpg",
+        params: params
+      )
+
+      expect(signature1).to eq(signature2)
+    end
+
+    it "generates different signatures for different inputs" do
+      signature1 = Fileboost::SignatureGenerator.generate(
+        asset_path: "/test/path1.jpg",
+        params: { "w" => "300" }
+      )
+
+      signature2 = Fileboost::SignatureGenerator.generate(
+        asset_path: "/test/path2.jpg",
+        params: { "w" => "300" }
+      )
+
+      expect(signature1).not_to eq(signature2)
+    end
+
+    it "parameter order does not affect signature" do
+      signature1 = Fileboost::SignatureGenerator.generate(
+        asset_path: "/test/path.jpg",
+        params: { "w" => "300", "h" => "200" }
+      )
+
+      signature2 = Fileboost::SignatureGenerator.generate(
+        asset_path: "/test/path.jpg",
+        params: { "h" => "200", "w" => "300" }
+      )
+
+      expect(signature1).to eq(signature2)
+    end
+  end
+end
diff --git a/spec/fileboost/url_builder_spec.rb b/spec/fileboost/url_builder_spec.rb
new file mode 100644
index 0000000..44c7fb5
--- /dev/null
+++ b/spec/fileboost/url_builder_spec.rb
@@ -0,0 +1,104 @@
+require "spec_helper"
+
+RSpec.describe Fileboost::UrlBuilder do
+  let(:user) { User.create!(name: "Test User") }
+  let(:blob) do
+    ActiveStorage::Blob.create_and_upload!(
+      io: StringIO.new("fake image data"),
+      filename: "test.jpg",
+      content_type: "image/jpeg"
+    )
+  end
+
+  before do
+    Fileboost.configure do |config|
+      config.project_id = "test_project"
+      config.token = "test_token"
+    end
+  end
+
+  describe ".build_url" do
+    context "with valid ActiveStorage::Blob" do
+      it "builds a URL with signature" do
+        url = Fileboost::UrlBuilder.build_url(blob, resize: { w: 300, h: 200 })
+
+        expect(url).to include("https://cdn.fileboost.dev")
+        expect(url).to include("test_project")
+        expect(url).to include("sig=")
+        expect(url).to include("w=300")
+        expect(url).to include("h=200")
+      end
+    end
+
+    context "with ActiveStorage attachment" do
+      it "builds a URL for has_one_attached" do
+        user.avatar.attach(blob)
+
+        url = Fileboost::UrlBuilder.build_url(user.avatar, resize: { w: 300 })
+
+        expect(url).to include("https://cdn.fileboost.dev")
+        expect(url).to include("w=300")
+        expect(url).to include("sig=")
+      end
+    end
+
+    context "with invalid configuration" do
+      it "raises ConfigurationError when config is invalid" do
+        Fileboost.config.project_id = ""
+
+        expect {
+          Fileboost::UrlBuilder.build_url(blob)
+        }.to raise_error(Fileboost::ConfigurationError)
+      end
+    end
+
+    context "with unsupported asset type" do
+      it "raises AssetPathExtractionError" do
+        expect {
+          Fileboost::UrlBuilder.build_url("invalid_asset")
+        }.to raise_error(Fileboost::AssetPathExtractionError)
+      end
+    end
+  end
+
+  describe ".extract_transformation_params" do
+    it "extracts and normalizes resize parameters" do
+      options = { resize: { width: 300, height: 200, quality: 85, format: "webp" } }
+
+      params = Fileboost::UrlBuilder.send(:extract_transformation_params, options)
+
+      expect(params["w"]).to eq("300")
+      expect(params["h"]).to eq("200")
+      expect(params["q"]).to eq("85")
+      expect(params["f"]).to eq("webp")
+    end
+
+    it "ignores invalid parameters" do
+      options = { resize: { invalid_param: "value", w: 300 } }
+
+      params = Fileboost::UrlBuilder.send(:extract_transformation_params, options)
+
+      expect(params).not_to have_key("invalid_param")
+      expect(params["w"]).to eq("300")
+    end
+  end
+
+  describe ".normalize_param_value" do
+    it "normalizes numeric parameters" do
+      expect(Fileboost::UrlBuilder.send(:normalize_param_value, "w", 300)).to eq("300")
+      expect(Fileboost::UrlBuilder.send(:normalize_param_value, "q", "85")).to eq("85")
+      expect(Fileboost::UrlBuilder.send(:normalize_param_value, "w", 0)).to be_nil
+    end
+
+    it "validates format parameter" do
+      expect(Fileboost::UrlBuilder.send(:normalize_param_value, "f", "webp")).to eq("webp")
+      expect(Fileboost::UrlBuilder.send(:normalize_param_value, "f", "invalid")).to be_nil
+    end
+
+    it "validates fit parameter" do
+      expect(Fileboost::UrlBuilder.send(:normalize_param_value, "fit", "cover")).to eq("cover")
+      expect(Fileboost::UrlBuilder.send(:normalize_param_value, "fit", "scale_down")).to eq("scale-down")
+      expect(Fileboost::UrlBuilder.send(:normalize_param_value, "fit", "invalid")).to be_nil
+    end
+  end
+end
diff --git a/spec/fileboost_spec.rb b/spec/fileboost_spec.rb
new file mode 100644
index 0000000..88e9bd2
--- /dev/null
+++ b/spec/fileboost_spec.rb
@@ -0,0 +1,32 @@
+require "spec_helper"
+
+RSpec.describe Fileboost do
+  it "has a version number" do
+    expect(Fileboost::VERSION).not_to be nil
+  end
+
+  describe ".configure" do
+    it "yields configuration object" do
+      expect { |b| Fileboost.configure(&b) }.to yield_with_args(Fileboost::Config)
+    end
+
+    it "allows setting configuration values" do
+      Fileboost.configure do |config|
+        config.project_id = "new_project"
+        config.token = "new_token"
+      end
+
+      expect(Fileboost.config.project_id).to eq("new_project")
+      expect(Fileboost.config.token).to eq("new_token")
+    end
+  end
+
+  describe ".config" do
+    it "returns the same configuration instance" do
+      config1 = Fileboost.config
+      config2 = Fileboost.config
+
+      expect(config1).to be(config2)
+    end
+  end
+end
diff --git a/spec/internal/app/models/application_record.rb b/spec/internal/app/models/application_record.rb
new file mode 100644
index 0000000..b63caeb
--- /dev/null
+++ b/spec/internal/app/models/application_record.rb
@@ -0,0 +1,3 @@
+class ApplicationRecord < ActiveRecord::Base
+  primary_abstract_class
+end
diff --git a/spec/internal/app/models/user.rb b/spec/internal/app/models/user.rb
new file mode 100644
index 0000000..74ea160
--- /dev/null
+++ b/spec/internal/app/models/user.rb
@@ -0,0 +1,4 @@
+class User < ApplicationRecord
+  has_one_attached :avatar
+  has_many_attached :images
+end
diff --git a/spec/internal/config/database.yml b/spec/internal/config/database.yml
new file mode 100644
index 0000000..235a242
--- /dev/null
+++ b/spec/internal/config/database.yml
@@ -0,0 +1,3 @@
+test:
+  adapter: sqlite3
+  database: ":memory:"
\ No newline at end of file
diff --git a/spec/internal/config/routes.rb b/spec/internal/config/routes.rb
new file mode 100644
index 0000000..18f456b
--- /dev/null
+++ b/spec/internal/config/routes.rb
@@ -0,0 +1,3 @@
+Rails.application.routes.draw do
+  # Routes for testing purposes
+end
diff --git a/spec/internal/config/storage.yml b/spec/internal/config/storage.yml
new file mode 100644
index 0000000..d2bf1b6
--- /dev/null
+++ b/spec/internal/config/storage.yml
@@ -0,0 +1,3 @@
+test:
+  service: Disk
+  root: <%= Rails.root.join("tmp/storage") %>
\ No newline at end of file
diff --git a/spec/internal/db/schema.rb b/spec/internal/db/schema.rb
new file mode 100644
index 0000000..7b0a8c2
--- /dev/null
+++ b/spec/internal/db/schema.rb
@@ -0,0 +1,37 @@
+ActiveRecord::Schema.define do
+  # Schema for testing ActiveStorage functionality
+  create_table "active_storage_blobs", force: :cascade do |t|
+    t.string   "key",          null: false
+    t.string   "filename",     null: false
+    t.string   "content_type"
+    t.text     "metadata"
+    t.string   "service_name", null: false
+    t.bigint   "byte_size",    null: false
+    t.string   "checksum"
+    t.datetime "created_at",   null: false
+    t.index [ "key" ], name: "index_active_storage_blobs_on_key", unique: true
+  end
+
+  create_table "active_storage_attachments", force: :cascade do |t|
+    t.string     "name",     null: false
+    t.references "record",   null: false, polymorphic: true, index: false
+    t.references "blob",     null: false
+    t.datetime   "created_at", null: false
+    t.index [ "record_type", "record_id", "name", "blob_id" ], name: "index_active_storage_attachments_uniqueness", unique: true
+    t.foreign_key "active_storage_blobs", column: "blob_id"
+  end
+
+  create_table "active_storage_variant_records", force: :cascade do |t|
+    t.belongs_to "blob", null: false, index: false
+    t.string     "variation_digest", null: false
+    t.index [ "blob_id", "variation_digest" ], name: "index_active_storage_variant_records_uniqueness", unique: true
+    t.foreign_key "active_storage_blobs", column: "blob_id"
+  end
+
+  # Test model for ActiveStorage attachments
+  create_table "users", force: :cascade do |t|
+    t.string   "name"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+  end
+end
diff --git a/spec/internal/log/test.log b/spec/internal/log/test.log
new file mode 100644
index 0000000..e69de29
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
new file mode 100644
index 0000000..f297737
--- /dev/null
+++ b/spec/spec_helper.rb
@@ -0,0 +1,54 @@
+require "bundler/setup"
+
+# Configure Rails Environment
+ENV["RAILS_ENV"] = "test"
+
+require "combustion"
+
+# Initialize Combustion with the components we need
+Combustion.initialize! :active_storage, :action_controller, :action_view do
+  config.load_defaults Rails::VERSION::STRING.to_f
+
+  # Configure Active Storage for testing
+  config.active_storage.variant_processor = :mini_magick
+  config.active_storage.service = :test
+end
+
+require "rspec/rails"
+require "fileboost"
+
+RSpec.configure do |config|
+  # Enable flags like --only-failures and --next-failure
+  config.example_status_persistence_file_path = ".rspec_status"
+
+  # Disable RSpec exposing methods globally on Module and main
+  config.disable_monkey_patching!
+
+  config.expect_with :rspec do |c|
+    c.syntax = :expect
+  end
+
+  # Include Rails test helpers
+  config.include Rails.application.routes.url_helpers
+
+  # Set up database before suite
+  config.before(:suite) do
+    Rails.logger.level = Logger::WARN unless ENV["VERBOSE"]
+
+    # Ensure database tables are created
+    ActiveRecord::Schema.verbose = false
+    load Rails.root.join("db", "schema.rb")
+  end
+
+  # Clean up after each test
+  config.around(:each) do |example|
+    # Reset Fileboost configuration before each test
+    Fileboost.instance_variable_set(:@config, nil)
+
+    # Run test in a transaction that gets rolled back
+    ActiveRecord::Base.transaction do
+      example.run
+      raise ActiveRecord::Rollback
+    end
+  end
+end
diff --git a/test/fileboost_test.rb b/test/fileboost_test.rb
deleted file mode 100644
index 3e9f3df..0000000
--- a/test/fileboost_test.rb
+++ /dev/null
@@ -1,40 +0,0 @@
-require "test_helper"
-
-class FileboostTest < ActiveSupport::TestCase
-  def setup
-    # Reset configuration for each test
-    Fileboost.config.project_id = "test-project"
-    Fileboost.config.token = "test-token"
-  end
-
-  test "it has a version number" do
-    assert Fileboost::VERSION
-  end
-
-  test "configuration can be set via block" do
-    Fileboost.configure do |config|
-      config.project_id = "new-project"
-      config.token = "new-token"
-    end
-
-    assert_equal "new-project", Fileboost.config.project_id
-    assert_equal "new-token", Fileboost.config.token
-  end
-
-  test "configuration validates required fields" do
-    Fileboost.config.project_id = nil
-    assert_not Fileboost.config.valid?
-
-    Fileboost.config.project_id = "test"
-    Fileboost.config.token = nil
-    assert_not Fileboost.config.valid?
-
-    Fileboost.config.token = "test"
-    assert Fileboost.config.valid?
-  end
-
-  test "base_url is hardcoded to cdn.fileboost.dev" do
-    assert_equal "https://cdn.fileboost.dev", Fileboost.config.base_url
-    assert_equal "cdn.fileboost.dev", Fileboost::Config::CDN_DOMAIN
-  end
-end
diff --git a/test/resize_parameter_test.rb b/test/resize_parameter_test.rb
deleted file mode 100644
index 4a76513..0000000
--- a/test/resize_parameter_test.rb
+++ /dev/null
@@ -1,99 +0,0 @@
-require "test_helper"
-
-class ResizeParameterTest < ActiveSupport::TestCase
-  def setup
-    Fileboost.config.project_id = "test-project"
-    Fileboost.config.token = "test-secret-key"
-  end
-
-  test "extract_transformation_params handles resize parameter" do
-    options = {
-      resize: {
-        width: 400,
-        height: 300,
-        quality: 85,
-        format: :webp
-      },
-      class: "hero-image"
-    }
-
-    params = Fileboost::UrlBuilder.send(:extract_transformation_params, options)
-
-    assert_equal "400", params["w"]
-    assert_equal "300", params["h"] 
-    assert_equal "85", params["q"]
-    assert_equal "webp", params["f"]
-    assert_nil params["class"] # Should not be included in transformation params
-  end
-
-  test "extract_transformation_params handles short parameter names in resize" do
-    options = {
-      resize: {
-        w: 400,
-        h: 300,
-        q: 85,
-        f: :webp
-      }
-    }
-
-    params = Fileboost::UrlBuilder.send(:extract_transformation_params, options)
-
-    assert_equal "400", params["w"]
-    assert_equal "300", params["h"]
-    assert_equal "85", params["q"] 
-    assert_equal "webp", params["f"]
-  end
-
-  test "extract_transformation_params ignores direct parameters without resize" do
-    options = {
-      width: 500,
-      height: 400,
-      quality: 90
-    }
-
-    params = Fileboost::UrlBuilder.send(:extract_transformation_params, options)
-
-    # Should be empty since no resize parameter
-    assert_empty params
-  end
-
-  test "extract_transformation_params ignores invalid resize parameters" do
-    options = {
-      resize: {
-        width: 400,
-        invalid_param: "ignored",
-        height: 300
-      }
-    }
-
-    params = Fileboost::UrlBuilder.send(:extract_transformation_params, options)
-
-    assert_equal "400", params["w"]
-    assert_equal "300", params["h"]
-    assert_nil params["invalid_param"]
-  end
-
-  test "extract_transformation_params handles empty resize parameter" do
-    options = {
-      resize: {},
-      width: 400  # Should be ignored
-    }
-
-    params = Fileboost::UrlBuilder.send(:extract_transformation_params, options)
-
-    # Should be empty since resize parameter is empty hash
-    assert_empty params
-  end
-
-  test "extract_transformation_params handles non-hash resize parameter" do
-    options = {
-      resize: "invalid",
-      width: 400
-    }
-
-    params = Fileboost::UrlBuilder.send(:extract_transformation_params, options)
-
-    # Should be empty since resize parameter is not a hash
-    assert_empty params
-  end
-end
\ No newline at end of file
diff --git a/test/signature_generator_test.rb b/test/signature_generator_test.rb
deleted file mode 100644
index a5125f0..0000000
--- a/test/signature_generator_test.rb
+++ /dev/null
@@ -1,95 +0,0 @@
-require "test_helper"
-
-class SignatureGeneratorTest < ActiveSupport::TestCase
-  def setup
-    Fileboost.config.token = "test-secret-key"
-  end
-
-  test "generates consistent signatures for same inputs" do
-    signature1 = Fileboost::SignatureGenerator.generate(
-      project_id: "test-project",
-      asset_path: "/test/image.jpg",
-      params: { w: "400", h: "300" }
-    )
-
-    signature2 = Fileboost::SignatureGenerator.generate(
-      project_id: "test-project",
-      asset_path: "/test/image.jpg",
-      params: { w: "400", h: "300" }
-    )
-
-    assert_equal signature1, signature2
-    assert signature1.present?
-  end
-
-  test "generates different signatures for different inputs" do
-    signature1 = Fileboost::SignatureGenerator.generate(
-      project_id: "test-project",
-      asset_path: "/test/image1.jpg",
-      params: { w: "400", h: "300" }
-    )
-
-    signature2 = Fileboost::SignatureGenerator.generate(
-      project_id: "test-project",
-      asset_path: "/test/image2.jpg",
-      params: { w: "400", h: "300" }
-    )
-
-    assert_not_equal signature1, signature2
-  end
-
-  test "parameter order does not affect signature" do
-    signature1 = Fileboost::SignatureGenerator.generate(
-      project_id: "test-project",
-      asset_path: "/test/image.jpg",
-      params: { w: "400", h: "300", q: "85" }
-    )
-
-    signature2 = Fileboost::SignatureGenerator.generate(
-      project_id: "test-project",
-      asset_path: "/test/image.jpg",
-      params: { q: "85", h: "300", w: "400" }
-    )
-
-    assert_equal signature1, signature2
-  end
-
-  test "returns nil when token is missing" do
-    Fileboost.config.token = nil
-
-    signature = Fileboost::SignatureGenerator.generate(
-      project_id: "test-project",
-      asset_path: "/test/image.jpg",
-      params: { w: "400" }
-    )
-
-    assert_nil signature
-  end
-
-  test "signature verification works correctly" do
-    params = { w: "400", h: "300" }
-    signature = Fileboost::SignatureGenerator.generate(
-      project_id: "test-project",
-      asset_path: "/test/image.jpg",
-      params: params
-    )
-
-    assert Fileboost::SignatureGenerator.verify_signature(
-      project_id: "test-project",
-      asset_path: "/test/image.jpg",
-      params: params,
-      signature: signature
-    )
-  end
-
-  test "signature verification fails with wrong signature" do
-    params = { w: "400", h: "300" }
-
-    assert_not Fileboost::SignatureGenerator.verify_signature(
-      project_id: "test-project",
-      asset_path: "/test/image.jpg",
-      params: params,
-      signature: "wrong-signature"
-    )
-  end
-end
\ No newline at end of file
diff --git a/test/test_helper.rb b/test/test_helper.rb
deleted file mode 100644
index cf669c8..0000000
--- a/test/test_helper.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-# Configure Rails Environment
-ENV["RAILS_ENV"] = "test"
-
-require_relative "../test/dummy/config/environment"
-ActiveRecord::Migrator.migrations_paths = [ File.expand_path("../test/dummy/db/migrate", __dir__) ]
-ActiveRecord::Migrator.migrations_paths << File.expand_path("../db/migrate", __dir__)
-require "rails/test_help"
-
-# Load fixtures from the engine
-if ActiveSupport::TestCase.respond_to?(:fixture_paths=)
-  ActiveSupport::TestCase.fixture_paths = [ File.expand_path("fixtures", __dir__) ]
-  ActionDispatch::IntegrationTest.fixture_paths = ActiveSupport::TestCase.fixture_paths
-  ActiveSupport::TestCase.file_fixture_path = File.expand_path("fixtures", __dir__) + "/files"
-  ActiveSupport::TestCase.fixtures :all
-end
diff --git a/test/url_builder_test.rb b/test/url_builder_test.rb
deleted file mode 100644
index 050d6de..0000000
--- a/test/url_builder_test.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require "test_helper"
-
-class UrlBuilderTest < ActiveSupport::TestCase
-  def setup
-    Fileboost.config.project_id = "test-project"
-    Fileboost.config.token = "test-secret-key"
-  end
-
-  test "returns nil for non-ActiveStorage objects" do
-    url = Fileboost::UrlBuilder.build_url("/test/image.jpg", width: 400, height: 300)
-    assert_nil url
-
-    url = Fileboost::UrlBuilder.build_url("image.jpg", width: 400)
-    assert_nil url
-  end
-
-  test "returns nil when configuration is invalid" do
-    Fileboost.config.project_id = nil
-    
-    url = Fileboost::UrlBuilder.build_url("any-object", width: 400)
-    
-    assert_nil url
-  end
-end
\ No newline at end of file