Switch browser to offline mode

Author: route

CHANGELOG.md

@@ -20,6 +20,8 @@ a block with this page, after which the page is closed.
 - Windows support
 - Show warning and accept dialog if no handler given
 - `Ferrum::Cookies#set` ability to set cookie using `Ferrum::Cookies::Cookie` object
+- `Ferrum::Network#emulate_network_conditions` activates emulation of network conditions
+- `Ferrum::Network#offline_mode` puts browser into offline mode
 
 ### Changed
 

README.md

@@ -561,13 +561,41 @@ end
 browser.network.authorize(user: "login", password: "pass", type: :proxy)
 
 browser.go_to("https://google.com")
-
 ```
 
 You used to call `authorize` method without block, but since it's implemented using request interception there could be
 a collision with another part of your code that also uses request interception, so that authorize allows the request
 while your code denies but it's too late. The block is mandatory now.
 
+#### emulate_network_conditions(\*\*options)
+
+Activates emulation of network conditions.
+
+* options `Hash`
+  * :offline `Boolean` emulate internet disconnection, `false` by default
+  * :latency `Integer` minimum latency from request sent to response headers received (ms), `0` by
+    default
+  * :download_throughput `Integer` maximal aggregated download throughput (bytes/sec), `-1`
+    by default, disables download throttling
+  * :upload_throughput `Integer` maximal aggregated upload throughput (bytes/sec), `-1`
+    by default, disables download throttling
+  * :connection_type `String` connection type if known, one of: none, cellular2g, cellular3g, cellular4g,
+    bluetooth, ethernet, wifi, wimax, other. `nil` by default
+
+```ruby
+browser.network.emulate_network_conditions(connection_type: "cellular2g")
+browser.go_to("https://github.com/")
+```
+
+#### offline_mode
+
+Activates offline mode for a page.
+
+```ruby
+browser.network.offline_mode
+browser.go_to("https://github.com/") # => Ferrum::StatusError (Request to https://github.com/ failed to reach server, check DNS and server status)
+```
+
 
 ## Proxy
 

lib/ferrum/network.rb

@@ -17,6 +17,7 @@ class Network
     AUTHORIZE_BLOCK_MISSING = "Block is missing, call `authorize(...) { |r| r.continue } "\
                               "or subscribe to `on(:request)` events before calling it"
     AUTHORIZE_TYPE_WRONG = ":type should be in #{AUTHORIZE_TYPE}"
+    ALLOWED_CONNECTION_TYPE = %w[none cellular2g cellular3g cellular4g bluetooth ethernet wifi wimax other].freeze
 
     attr_reader :traffic
 
@@ -150,6 +151,25 @@ def build_exchange(id)
       Network::Exchange.new(@page, id).tap { |e| @traffic << e }
     end
 
+    def emulate_network_conditions(offline: false, latency: 0, download_throughput: -1, upload_throughput: -1, connection_type: nil)
+      params = {
+        offline: offline, latency: latency,
+        downloadThroughput: download_throughput,
+        uploadThroughput: upload_throughput
+      }
+
+      if connection_type && ALLOWED_CONNECTION_TYPE.include?(connection_type)
+        params[:connectionType] = connection_type
+      end
+
+      @page.command("Network.emulateNetworkConditions", params)
+      true
+    end
+
+    def offline_mode
+      emulate_network_conditions(offline: true, latency: 0, download_throughput: 0, upload_throughput: 0)
+    end
+
     private
 
     def subscribe_request_will_be_sent

spec/network_spec.rb

@@ -393,5 +393,25 @@ module Ferrum
         expect(page.body).to include("Authorized POST request")
       end
     end
+
+    it "#emulate_network_conditions", skip: "doesn't work for now" do
+      page.network.emulate_network_conditions(latency: 500)
+
+      start = Utils::ElapsedTime.monotonic_time
+      page.go_to("/ferrum/with_js")
+
+      expect(Utils::ElapsedTime.elapsed_time(start)).to eq(2000)
+    end
+
+    it "#offline_mode" do
+      page.network.offline_mode
+
+      expect { page.go_to("/ferrum/with_js") }.to raise_error(
+                                                    Ferrum::StatusError,
+                                                    %r{Request to http://.*/ferrum/with_js failed to reach server, check DNS and server status}
+                                                  )
+
+      expect(page.body).to eq("<html><head></head><body></body></html>")
+    end
   end
 end

spec/spec_helper.rb

@@ -30,6 +30,7 @@
     base_url = Ferrum::Server.server.base_url
     options = { base_url: base_url }
     options.merge!(headless: false) if ENV["HEADLESS"] == "false"
+    options.merge!(slowmo: ENV["SLOWMO"].to_f) if ENV["SLOWMO"].to_f > 0
 
     if ENV["CI"]
       ferrum_logger = StringIO.new