fix: Safari noSuchWindowException and Page/Frame not ready (#385)

QA Notes:

The following code occasionally caused Safari to throw a
`noSuchWindowException` around 1 in 10 times, and I expect it never to
do so now.

```
require "selenium-webdriver"
require_relative "../../lib/axe/api/run"
require "json"


driver = Selenium::WebDriver.for :safari
# driver.navigate.to "http://google.com"
driver.navigate.to "https://dequeuniversity.com/demo/mars/"

res = Axe::Core.new(driver).call Axe::API::Run.new.with_options

puts JSON.pretty_generate res.results.to_h

driver.quit
```

Note the commented `# driver.navigate to "http://google.com"`. Issue
#353 notes that attempting to navigate to `http://google.com` would also
occasionally cause an exception "Page/Frame not ready" to be thrown; it
should no longer do so.

Please uncomment this line, comment `driver.navigate.to
"https://dequeuniversity.com/demo/mars/"` and test again. This fix is
included here since they are closely related.

Closes: #352
Closes: #353

packages/axe-core-api/e2e/selenium/spec/api_spec.rb

@@ -307,6 +307,19 @@ def get_check_by_id(check_list, id)
     }
   end
 
+  it "throws an error if the window handle can't be found" do
+    # this is to cause execute_script to run twice, thus creating one extra window when it's called with `window.open` and making the handle undeterminable
+    allow($driver).to receive(:execute_script).and_wrap_original do |original_method, *args, &block|
+      original_method.call(*args, &block)
+      original_method.call(*args, &block)
+    end
+
+    $driver.get fixture "/index.html"
+    with_js($axe_post_43x) {
+      expect { run_axe }.to raise_error /Unable to determine window handle/
+    }
+  end
+
   it "works with large results", :nt => true do
     $driver.get fixture "/index.html"
     res = with_js($axe_post_43x + $large_partial_js) { run_axe }
@@ -317,6 +330,38 @@ def get_check_by_id(check_list, id)
   end
 end
 
+describe "does not throw when given" do
+  it "chromedriver" do
+    options = Selenium::WebDriver::Chrome::Options.new
+    options.add_argument('--no-sandbox')
+    options.add_argument('--disable-dev-shm-usage')
+    driver = Selenium::WebDriver.for :chrome, options: options
+    expect do 
+      driver.get fixture "/index.html"
+      driver.get "about:blank"
+    end.not_to raise_error
+  end
+
+  it "geckodriver" do
+    options = Selenium::WebDriver::Firefox::Options.new
+    options.add_argument('--headless')
+    driver = Selenium::WebDriver.for :firefox, options: options
+    expect do 
+      driver.get fixture "/index.html"
+      driver.get "about:blank"
+    end.not_to raise_error
+  end
+
+  if Object::RUBY_PLATFORM =~ /darwin/i
+    it "safaridriver" do
+      driver = Selenium::WebDriver.for :safari
+      expect do 
+        driver.get fixture "/index.html"
+        driver.get "about:blank"
+      end.not_to raise_error
+    end
+  end
+end
 
 describe "run vs runPartial" do
   it "should return the same results" do

packages/axe-core-api/lib/axe/api/run.rb

@@ -87,22 +87,28 @@ def switch_to_parent_frame(page)
 
       def within_about_blank_context(page)
         driver = get_selenium page
+        # This is a workaround to maintain Selenium 3 support
+        # Likely driver.switch_to.new_window(:tab) should be used instead, should we drop support, as per
+        # https://github.com/dequelabs/axe-core-gems/issues/352
 
-        num_handles = page.window_handles.length
+        before_handles = page.window_handles
         begin
           driver.execute_script("window.open('about:blank'), '_blank'")
-          if num_handles == page.window_handles.length
-            raise StandardError.new "Could not open new window. Please make sure that you have popup blockers disabled."
-          end
-          driver.switch_to.window page.window_handles[-1]
         rescue
-            raise StandardError.new "switchToWindow failed. Are you using updated browser drivers? Please check out https://github.com/dequelabs/axe-core-gems/blob/develop/error-handling.md"
+          raise StandardError.new "switchToWindow failed. Are you using updated browser drivers? Please check out https://github.com/dequelabs/axe-core-gems/blob/develop/error-handling.md"
+        end
+        after_handles = page.window_handles
+        new_handles = after_handles.difference(before_handles)
+        if new_handles.length != 1
+          raise StandardError.new "Unable to determine window handle"
         end
+        new_handle = new_handles[0]
+        driver.switch_to.window new_handle
         driver.get "about:blank"
 
         ret = yield page
 
-        driver.switch_to.window page.window_handles[-1]
+        driver.switch_to.window new_handle
         driver.close
         driver.switch_to.window @original_window
 

packages/axe-core-api/lib/axe/core.rb

@@ -38,22 +38,8 @@ def use_run_partial
       Core.has_run_partial?(@page) and not Axe::Configuration.instance.legacy_mode
     end
 
-    def assert_frame_ready
-      begin
-        ready = Timeout.timeout(10) {
-          @page.evaluate_script <<-JS
-            document.readyState === 'complete'
-          JS
-        }
-      rescue Timeout::Error
-        ready = false
-      end
-      raise Exception.new "Page/frame not ready" if not ready
-    end
-
     def load_axe_core(source)
       return if already_loaded?
-      assert_frame_ready
       loader = Common::Loader.new(@page, self)
       loader.load_top_level source
       return if use_run_partial

packages/axe-core-api/spec/axe/core_spec.rb

@@ -7,8 +7,7 @@ module Axe
     let(:page) {
       spy("page", evaluate_script: false)
     }
-    before { allow(page).to receive(:evaluate_script).and_return(false, true, false) }
-
+    before { allow(page).to receive(:evaluate_script).and_return(false, 'complete', false) }
     describe "initialize" do
       # We have removed comments from `axe.min.js`, so excluding this test
       # Hence cannot do start_with("/*! aXe"), instead do a function we know should exist check
@@ -25,6 +24,14 @@ module Axe
           expect(page).not_to have_received(:execute_script)
         end
       end
+
+      context "when document.readyState is interactive" do
+        before { allow(page).to receive(:evaluate_script).and_return(false, 'interactive', 'interactive', 'complete') }
+        it "should check ready frame until complete, then proceed" do
+          described_class.new(page)
+          expect(page).to have_received(:execute_script).with(a_string_including ("axe.run="))
+        end
+      end
     end
 
     describe "call" do