diff --git a/lib/gastly.rb b/lib/gastly.rb
index 41d5e3d..a759625 100644
--- a/lib/gastly.rb
+++ b/lib/gastly.rb
@@ -1,3 +1,8 @@
+require 'phantomjs'
+require 'mini_magick'
+require 'active_support/core_ext/hash/keys'
+require 'active_support/core_ext/object/blank'
+
 require_relative 'gastly/image'
 require_relative 'gastly/screenshot'
 require_relative 'gastly/exceptions'
diff --git a/lib/gastly/exceptions.rb b/lib/gastly/exceptions.rb
index 0b3eda2..44e44d6 100644
--- a/lib/gastly/exceptions.rb
+++ b/lib/gastly/exceptions.rb
@@ -8,4 +8,5 @@ def initialize(url)
   end
 
   PhantomJSError = Class.new(RuntimeError)
+  UnknownError   = Class.new(RuntimeError)
 end
diff --git a/lib/gastly/image.rb b/lib/gastly/image.rb
index dd3b322..b775ed7 100644
--- a/lib/gastly/image.rb
+++ b/lib/gastly/image.rb
@@ -1,33 +1,29 @@
-require 'mini_magick'
-
 module Gastly
   class Image
-    attr_reader :file
+    attr_reader :image
 
-    # @param tempfile [Tempfile] Screenshot
-    def initialize(tempfile)
-      @file = MiniMagick::Image.open(tempfile.path)
-      tempfile.unlink
+    # @param image [MiniMagick::Image] Instance of MiniMagick::Image
+    def initialize(image)
+      @image = image
     end
 
-    # @param [Hash]
-    # @option width [Fixnum] Image width
-    # @option height [Fixnum] Image height
+    # @param width [Fixnum] Image width
+    # @param height [Fixnum] Image height
     def resize(width:, height:)
       dimensions = "#{width}x#{height}"
-      @file.resize(dimensions)
+      image.resize(dimensions)
     end
 
     # @param ext [String] Image extension
     # @return [MiniMagick::Image] Instance
     def format(ext)
-      @file.format(ext)
+      image.format(ext)
     end
 
-    # @param output [String] Full path to file
-    # @return [String] Full path to file
+    # @param output [String] Full path to image
+    # @return [String] Full path to image
     def save(output)
-      @file.write(output)
+      image.write(output)
       output
     end
   end
diff --git a/lib/gastly/screenshot.rb b/lib/gastly/screenshot.rb
index f249a72..ad85bac 100644
--- a/lib/gastly/screenshot.rb
+++ b/lib/gastly/screenshot.rb
@@ -1,17 +1,12 @@
-require 'phantomjs'
-require 'active_support/core_ext/hash/keys'
-require 'active_support/core_ext/object/blank'
-
 module Gastly
   class Screenshot
     SCRIPT_PATH = File.expand_path('../script.js', __FILE__)
     DEFAULT_TIMEOUT = 0
     DEFAULT_BROWSER_WIDTH = 1440
     DEFAULT_BROWSER_HEIGHT = 900
-    DEFAULT_FILE_NAME = 'output'.freeze
     DEFAULT_FILE_FORMAT = '.png'.freeze
 
-    attr_reader :tempfile
+    attr_reader :image
     attr_writer :timeout, :browser_width, :browser_height
     attr_accessor :url, :selector, :cookies, :proxy_host, :proxy_port
 
@@ -22,12 +17,11 @@ def initialize(url, **kwargs)
       @url = url
       @cookies = kwargs.delete(:cookies)
 
-      @tempfile = Tempfile.new([DEFAULT_FILE_NAME, DEFAULT_FILE_FORMAT]) # TODO: Use MiniMagick::Image.create instead
+      @image = MiniMagick::Image.create(DEFAULT_FILE_FORMAT, false) # Disable validation
 
       kwargs.each { |key, value| instance_variable_set(:"@#{key}", value) }
     end
 
-    #
     # Capture image via PhantomJS and save to output file
     #
     # @return [Gastly::Image] Instance of Gastly::Image
@@ -37,10 +31,9 @@ def capture
       Phantomjs.proxy_port = proxy_port if proxy_port
 
       output = Phantomjs.run(proxy_options, SCRIPT_PATH.to_s, *prepared_params)
+      handle_output(output)
 
-      handle_exception(output) if output.present? # TODO: Add test
-
-      Gastly::Image.new(tempfile) # TODO: Add test
+      Gastly::Image.new(image)
     end
 
     %w(timeout browser_width browser_height).each do |name|
@@ -63,26 +56,28 @@ def prepared_params
         timeout:  timeout,
         width:    browser_width,
         height:   browser_height,
-        output:   tempfile.path
+        output:   image.path
       }
 
       params[:selector] = selector if selector.present?
-      params[:cookies]  = hash_to_array(cookies).join(',') if cookies.present?
+      params[:cookies]  = parameterize(cookies).join(',') if cookies.present?
 
-      hash_to_array(params)
+      parameterize(params)
     end
 
-    # TODO: Rename method to parameterize
-    def hash_to_array(data)
-      data.map { |key, value| "#{key}=#{value}" }
+    # @param hash [Hash]
+    # @return [Array] Array of parameterized strings
+    def parameterize(hash)
+      hash.map { |key, value| "#{key}=#{value}" }
     end
 
-    # TODO: Rename to handle_output
-    def handle_exception(output)
+    def handle_output(output)
+      return unless output.present?
+
       error = case output
               when /^FetchError:(.+)/     then Gastly::FetchError
               when /^RuntimeError:(.+)/m  then Gastly::PhantomJSError
-              # TODO: Return unknown error
+              else UnknownError
               end
 
       fail error, Regexp.last_match(1)
diff --git a/spec/gastly/image_spec.rb b/spec/gastly/image_spec.rb
index fd7785c..0f42ee3 100644
--- a/spec/gastly/image_spec.rb
+++ b/spec/gastly/image_spec.rb
@@ -1,5 +1,37 @@
 require 'spec_helper'
 
 RSpec.describe Gastly::Image do
+  let(:image) { MiniMagick::Image.new('test.png') }
+  subject { Gastly::Image.new(image) }
 
+  context '#resize' do
+    it 'invokes method #resize with arguments' do
+      width, height = 100, 100
+      expect_any_instance_of(MiniMagick::Image).to receive(:resize).with("#{width}x#{height}")
+      subject.resize(width: 100, height: 100)
+    end
+  end
+
+  context '#format' do
+    it 'invokes method #format' do
+      ext = 'png'
+      expect_any_instance_of(MiniMagick::Image).to receive(:format).with(ext)
+      subject.format(ext)
+    end
+  end
+
+  context '#save' do
+    let(:output) { 'output.png' }
+    before do
+      expect_any_instance_of(MiniMagick::Image).to receive(:write).with(output)
+    end
+
+    it 'invokes method #write' do
+      subject.save(output)
+    end
+
+    it 'returns a string' do
+      expect(subject.save(output)).to eq output
+    end
+  end
 end
\ No newline at end of file
diff --git a/spec/gastly/screenshot_spec.rb b/spec/gastly/screenshot_spec.rb
index 4946126..b5a0296 100644
--- a/spec/gastly/screenshot_spec.rb
+++ b/spec/gastly/screenshot_spec.rb
@@ -20,7 +20,6 @@
   it { expect(Gastly::Screenshot::DEFAULT_TIMEOUT).to eq 0 }
   it { expect(Gastly::Screenshot::DEFAULT_BROWSER_WIDTH).to eq 1440 }
   it { expect(Gastly::Screenshot::DEFAULT_BROWSER_HEIGHT).to eq 900 }
-  it { expect(Gastly::Screenshot::DEFAULT_FILE_NAME).to eq 'output' }
   it { expect(Gastly::Screenshot::DEFAULT_FILE_FORMAT).to eq '.png' }
 
   context '#initialize' do
@@ -57,7 +56,7 @@
         "timeout=#{params[:timeout]}",
         "width=#{params[:browser_width]}",
         "height=#{params[:browser_height]}",
-        "output=#{screenshot.tempfile.path}",
+        "output=#{screenshot.image.path}",
         "selector=#{params[:selector]}",
         "cookies=#{cookies}"
       ]
@@ -65,6 +64,29 @@
       expect(Phantomjs).to receive(:run).with(*args)
       screenshot.capture
     end
+
+    it 'raises an exception if fetch error' do
+      url = 'h11p://google.com'
+      screenshot = Gastly::Screenshot.new(url)
+      expect { screenshot.capture }.to raise_error(Gastly::FetchError, "Unable to load #{url}")
+    end
+
+    it 'raises an exception if runtime error' do
+      expect(Phantomjs).to receive(:run).and_return('RuntimeError:test runtime error')
+      screenshot = Gastly::Screenshot.new(url)
+      expect { screenshot.capture }.to raise_error(Gastly::PhantomJSError, 'test runtime error')
+    end
+
+    it 'raises an exception if unknown error' do
+      expect(Phantomjs).to receive(:run).and_return('unknown error')
+      screenshot = Gastly::Screenshot.new(url)
+      expect { screenshot.capture }.to raise_error(Gastly::UnknownError)
+    end
+
+    it 'returns an instance of Gastly::Image' do
+      screenshot = Gastly::Screenshot.new(url)
+      expect(screenshot.capture).to be_instance_of Gastly::Image
+    end
   end
 
   context '#timeout' do
diff --git a/spec/gastly_spec.rb b/spec/gastly_spec.rb
index 90e6c2b..5988556 100644
--- a/spec/gastly_spec.rb
+++ b/spec/gastly_spec.rb
@@ -1,4 +1,22 @@
 require 'spec_helper'
 
 describe Gastly do
+  let(:url) { 'http://google.com' }
+
+  context '#screenshot' do
+    it 'returns an instance of Gastly::Screenshot' do
+      expect(Gastly.screenshot(url, timeout: 1000)).to be_instance_of Gastly::Screenshot
+    end
+  end
+
+  context '#capture' do
+    it 'creates a screenshot' do
+      tmp = 'spec/support/tmp'
+      path = "#{tmp}/output.png"
+      expect(Dir.glob("#{tmp}/*").length).to eq 0
+      Gastly.capture(url, path)
+      expect(Dir.glob("#{tmp}/*").length).to eq 1
+      FileUtils.rm Dir.glob("#{tmp}/*")
+    end
+  end
 end