change the way to run tests

Author: KazuCocoa

README.md

@@ -31,14 +31,14 @@ Run unit tests which check each method and command, URL, using the webmock.
 
 ```bash
 $ bundle install
-$ bundle exec parallel_test test/unit/
+$ UNIT_TEST=1 bundle exec parallel_test test/unit/
 ```
 
 or
 
 ```bash
 $ bundle install
-$ bundle exec rake test:unit
+$ UNIT_TEST=1 bundle exec rake test:unit
 ```
 
 ### Functional Tests

Rakefile

@@ -38,31 +38,27 @@ namespace :test do
   namespace :unit do
     desc('Run all iOS related unit tests in test directory')
     Rake::TestTask.new(:ios) do |t|
-      ENV['UNIT_TEST'] = '1'
       t.libs << 'test'
       t.libs << 'lib'
       t.test_files = FileList['test/unit/ios/**/*_test.rb']
     end
 
     desc('Run all Android related unit tests in test directory')
     Rake::TestTask.new(:android) do |t|
-      ENV['UNIT_TEST'] = '1'
       t.libs << 'test'
       t.libs << 'lib'
       t.test_files = FileList['test/unit/android/**/*_test.rb']
     end
 
     desc('Run all common related unit tests in test directory')
     Rake::TestTask.new(:common) do |t|
-      ENV['UNIT_TEST'] = '1'
       t.libs << 'test'
       t.libs << 'lib'
       t.test_files = FileList['test/unit/common/**/*_test.rb']
     end
 
     desc('Run all Windows related unit tests in test directory')
     Rake::TestTask.new(:windows) do |t|
-      ENV['UNIT_TEST'] = '1'
       t.libs << 'test'
       t.libs << 'lib'
       t.test_files = FileList['test/unit/windows/**/*_test.rb']

test/unit/driver_test.rb

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 require 'test_helper'
+require 'webmock/minitest'
 
 class AppiumLibCoreTest
   class DriverTest < Minitest::Test