implement Selenium::Helpers::Wait (#25)

spec/features/wait_spec.cr

@@ -0,0 +1,51 @@
+require "../spec_helper"
+
+describe Selenium::Helpers::Wait do
+  describe ".wait" do
+    it "success if true" do
+      TestServer.route "/home", <<-HTML
+        <div id="div"></div>
+      HTML
+
+      with_session do |session|
+        session.navigate_to("http://localhost:3002/home")
+
+        wait = Selenium::Helpers::Wait.new(timeout: 2.seconds, interval: 1.second)
+
+        wait.until { session.find_element(:css, "#div") }
+      end
+    end
+
+    it "raises an error if false" do
+      TestServer.route "/home", <<-HTML
+        <div id="div"></div>
+      HTML
+
+      with_session do |session|
+        session.navigate_to("http://localhost:3002/home")
+
+        wait = Selenium::Helpers::Wait.new(timeout: 2.seconds, interval: 1.second)
+
+        expect_raises(IO::TimeoutError, /timed out after 2 seconds \(no such element.*/) do
+          wait.until { session.find_element(:css, "#div1") }
+        end
+      end
+    end
+
+    it "raises an error with custom message" do
+      TestServer.route "/home", <<-HTML
+        <div id="div"></div>
+      HTML
+
+      with_session do |session|
+        session.navigate_to("http://localhost:3002/home")
+
+        wait = Selenium::Helpers::Wait.new(timeout: 2.seconds, interval: 1.second, message: "custom message")
+
+        expect_raises(IO::TimeoutError, /custom message \(no such element.*/) do
+          wait.until { session.find_element(:css, "#div1") }
+        end
+      end
+    end
+  end
+end

src/selenium/helpers/wait.cr

@@ -0,0 +1,50 @@
+class Selenium::Helpers::Wait
+  @timeout : Time::Span
+  @interval : Time::Span
+  @ignored = [] of Exception
+
+  # Create a new `Wait` instance.
+  #
+  # `timeout` - seconds to wait before timing out
+  # `interval` - seconds to sleep between polls
+  # `message` - exception mesage if timed out
+  # `ignored` - exceptions to ignore while polling
+  def initialize(@timeout = 5.seconds, @interval = 0.2.seconds, @ignored = [Selenium::Error], @message : String? = nil)
+  end
+
+  # Wait until the given block returns a `true` value.
+  # Otherwise raise an exception `IO::TimeoutError`.
+  #
+  # ```
+  # wait = Selenium::Helpers::Wait.new(timeout: 10.seconds, interval: 1.second)
+  # wait.until { session.document_manager.execute_script("return document.readyState;") == "complete" }
+  # ```
+  def until(&) : Nil
+    end_time = current_time + @timeout
+    last_error : Exception? = nil
+
+    until current_time > end_time
+      begin
+        result = yield
+
+        return result if result
+      rescue ex
+        last_error = ex
+
+        raise ex unless @ignored.includes?(ex.class)
+      end
+
+      sleep @interval
+    end
+
+    message = @message || "timed out after #{@timeout.seconds} seconds"
+
+    message = message + " (#{last_error.message})" if last_error
+
+    raise IO::TimeoutError.new(message)
+  end
+
+  private def current_time
+    Time.utc
+  end
+end