Use 'expect' format for tests

lib/capybara/spec/session/save_and_open_screenshot_spec.rb

@@ -7,8 +7,8 @@
 
   it 'opens file from the default directory', :requires => [:screenshot] do
     expected_file_regex = %r{capybara/capybara-\d+\.png}
-    @session.driver.stub(:save_screenshot)
-    Launchy.stub(:open)
+    allow(@session.driver).to receive(:save_screenshot)
+    allow(Launchy).to receive(:open)
 
     @session.save_and_open_screenshot
 
@@ -19,8 +19,8 @@
 
   it 'opens file from the provided directory', :requires => [:screenshot] do
     custom_path = 'screenshots/1.png'
-    @session.driver.stub(:save_screenshot)
-    Launchy.stub(:open)
+    allow(@session.driver).to receive(:save_screenshot)
+    allow(Launchy).to receive(:open)
 
     @session.save_and_open_screenshot(custom_path)
 
@@ -32,8 +32,8 @@
   context 'when launchy cannot be required' do
     it 'prints out a correct warning message', :requires => [:screenshot] do
       file_path = File.join(Dir.tmpdir, 'test.png')
-      @session.stub(:require).with('launchy').and_raise(LoadError)
-      @session.stub(:warn)
+      allow(@session).to receive(:require).with('launchy').and_raise(LoadError)
+      allow(@session).to receive(:warn)
 
       @session.save_and_open_screenshot(file_path)