Don't crash when a click closes the window (fixes #10)

lib/capybara-lockstep/client.rb

@@ -7,6 +7,7 @@ class Client
       ERROR_SNIPPET_MISSING = 'Cannot synchronize: capybara-lockstep JavaScript snippet is missing'
       ERROR_PAGE_MISSING = 'Cannot synchronize with empty page'
       ERROR_ALERT_OPEN = 'Cannot synchronize while an alert is open'
+      ERROR_WINDOW_CLOSED = 'Cannot synchronize with closed window'
       ERROR_NAVIGATED_AWAY = "Browser navigated away while synchronizing"
 
       SYNCHRONIZED_IVAR = :@lockstep_synchronized_client
@@ -94,7 +95,11 @@ def synchronize
           end
         rescue ::Selenium::WebDriver::Error::UnexpectedAlertOpenError
           log ERROR_ALERT_OPEN
-          # Don't raise an error, this will happen in an innocent test.
+          # Don't raise an error, this will happen in an innocent test where a click opens an alert.
+          # We will retry on the next Capybara synchronize call.
+        rescue ::Selenium::WebDriver::Error::NoSuchWindowError
+          log ERROR_WINDOW_CLOSED
+          # Don't raise an error, this will happen in an innocent test where a click closes a window.
           # We will retry on the next Capybara synchronize call.
         rescue ::Selenium::WebDriver::Error::JavascriptError => e
           # When the URL changes while a script is running, my current selenium-webdriver

lib/capybara-lockstep/page_access.rb

@@ -19,7 +19,7 @@ def alert_present?
         # to its `getLog` API. This causes Selenium to time out with a `Net::ReadTimeout` error
         page.driver.browser.switch_to.alert
         true
-      rescue Capybara::NotSupportedByDriverError, ::Selenium::WebDriver::Error::NoSuchAlertError
+      rescue Capybara::NotSupportedByDriverError, ::Selenium::WebDriver::Error::NoSuchAlertError, ::Selenium::WebDriver::Error::NoSuchWindowError
         false
       end
 

spec/features/synchronization_spec.rb

@@ -92,6 +92,26 @@
       page.accept_confirm('OK to proceed?')
     end
 
+    it 'does not crash if the click closes the window' do
+      App.start_html = <<~HTML
+        <a href="/start" target="_blank"">open window</a>
+        <a href="#" onclick="window.close()"">close window</a>
+      HTML
+
+      visit '/start'
+
+      window = window_opened_by do
+        find('a', text: 'open window').click
+      end
+
+      expect do
+        within_window(window) do
+          find('a', text: 'close window').click
+        end
+      end.to_not raise_error
+
+    end
+
   end
 
   describe 'when reading elements' do