Add a test to demonstrate that Proxy works

The current state of using a Proxy is both well-defined and variously
implemented.

* Chrome and ChromeDriver uses just the HTTP field with a host:port.

* Firefox via GeckoDriver directly requires that the host be provided in
  the HTTP field and the port be provided in the HTTPPort field.

* Firefox via Selenium 2 uses just the HTTP field, with the caveat that
  connections to localhost are not proxied, by default. An additional
  preference is needed to unset this.

* Firefox via Selenium 3 and GeckoDriver fails because Selenium adds a
  whole bunch of "nulls" for unset values in the Proxy object, which
  Marionette does not like. mozilla/geckodriver#490

Fixes #41.

README.md

@@ -77,6 +77,9 @@ one.
    implement this support](https://github.com/mozilla/geckodriver/issues/159).
    Then, [Selenium 3 doesn't implement this support for
    Firefox](https://github.com/SeleniumHQ/selenium/issues/2285).
+5. [The Proxy object is
+   misinterpreted](https://github.com/mozilla/geckodriver/issues/490) by
+   Geckodriver when passed through by Selenium 3.
 
 The Geckodriver team recommends using the newest available Firefox version, as
 the integration is actively being developed.

remote_test.go

@@ -7,10 +7,12 @@ import (
 	"net"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"reflect"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -485,6 +487,7 @@ func runTests(t *testing.T, c config) {
 	t.Run("ResizeWindow", runTest(testResizeWindow, c))
 	t.Run("KeyDownUp", runTest(testKeyDownUp, c))
 	t.Run("CSSProperty", runTest(testCSSProperty, c))
+	t.Run("Proxy", runTest(testProxy, c))
 }
 
 func testStatus(t *testing.T, c config) {
@@ -750,7 +753,7 @@ func testFindElement(t *testing.T, c config) {
 
 		we, ok := elem.(*remoteWE)
 		if !ok {
-			t.Errorf("wd.FindElement(%q, %q) = %T, want a *remoteWE", tc.by, tc.query)
+			t.Errorf("wd.FindElement(%q, %q) = %T, want a *remoteWE", tc.by, tc.query, elem)
 			continue
 		}
 
@@ -1363,6 +1366,87 @@ func testCSSProperty(t *testing.T, c config) {
 	t.Fatalf(`e.CSSProperty("color") = %q, want one of %q`, color, wantColors)
 }
 
+func testProxy(t *testing.T, c config) {
+	const pageContents = "You are viewing a proxied page"
+	s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		fmt.Fprintf(w, pageContents)
+	}))
+	defer s.Close()
+
+	u, err := url.Parse(s.URL)
+	if err != nil {
+		t.Fatalf("url.Parse(%q) returned error: %v", s.URL, err)
+	}
+
+	caps := newTestCapabilities(t, c)
+	proxy := Proxy{Type: Manual}
+	switch c.browser {
+	case "firefox":
+		switch c.seleniumVersion.Major {
+		case 0: // Geckodriver.
+			host, port, err := net.SplitHostPort(u.Host)
+			if err != nil {
+				t.Fatalf("net.SplitHostPort(%q) returned error: %v", u.Host, err)
+			}
+			p, err := strconv.Atoi(port)
+			if err != nil {
+				t.Fatalf("strconv.Atoi(%q) returned error: %v", port, err)
+			}
+			proxy.HTTP = host
+			proxy.HTTPPort = p
+		case 2:
+			proxy.HTTP = u.Host
+		case 3:
+			// When the Proxy object is passed through Selenium 3 to GeckoDriver, it
+			// adds a whole bunch of "null" values for empty entities. GeckoDriver
+			// does not interpret this well.
+			// https://github.com/mozilla/geckodriver/issues/490
+			t.Skip("Skipping test due to https://github.com/mozilla/geckodriver/issues/490")
+		}
+		// By default, Firefox explicitly does not use a proxy for connection to
+		// localhost and 127.0.0.1. Clear this preference to reach our test proxy.
+		ff, ok := caps[firefox.CapabilitiesKey].(firefox.Capabilities)
+		if ok { // Selenium 3.0.1 does not support Firefox capabilities.
+			if ff.Prefs == nil {
+				ff.Prefs = make(map[string]interface{})
+			}
+			ff.Prefs["network.proxy.no_proxies_on"] = ""
+			caps[firefox.CapabilitiesKey] = ff
+		}
+	case "chrome":
+		proxy.HTTP = u.Host
+	}
+	caps.AddProxy(proxy)
+
+	wd := &remoteWD{
+		capabilities: caps,
+		urlPrefix:    c.addr,
+	}
+	defer func() {
+		if err := wd.Quit(); err != nil {
+			t.Fatalf("wd.Quit() returned error: %v", err)
+		}
+	}()
+	if _, err := wd.NewSession(); err != nil {
+		t.Fatalf("wd.NewSession() returned error: %v", err)
+	}
+
+	if err := wd.Get(serverURL); err != nil {
+		t.Fatalf("wd.Get(%q) returned error: %v", serverURL, err)
+	}
+	source, err := wd.PageSource()
+	if err != nil {
+		t.Fatalf("wd.PageSource() returned error: %v", err)
+	}
+
+	if !strings.Contains(source, pageContents) {
+		if strings.Contains(source, "Go Selenium Test Suite") {
+			t.Fatal("Got non-proxied page.")
+		}
+		t.Fatalf("Got page: %s\n\nExpected: %q", source, pageContents)
+	}
+}
+
 var homePage = `
 <html>
 <head>

selenium.go

@@ -104,16 +104,25 @@ func (c Capabilities) AddFirefox(f firefox.Capabilities) {
 	c[firefox.CapabilitiesKey] = f
 }
 
+// AddProxy adds proxy configuration to the capabilities.
+func (c Capabilities) AddProxy(p Proxy) {
+	c["proxy"] = p
+}
+
 // Proxy specifies configuration for proxies in the browser. Set the key
 // "proxy" in Capabilities to an instance of this type.
 type Proxy struct {
+	// Type is the type of proxy to use. This is required to be populated.
 	Type ProxyType `json:"proxyType"`
 
 	// AutoconfigURL is the URL to be used for proxy auto configuration. This is
 	// required if Type is set to PAC.
 	AutoconfigURL string `json:"proxyAutoconfigUrl,omitempty"`
 
 	// The following are used when Type is set to Manual.
+	//
+	// Note that in Firefox, connections to localhost are not proxied by default,
+	// even if a proxy is set. This can be overrided via a preference setting.
 	FTP           string `json:"ftpProxy,omitempty"`
 	HTTP          string `json:"httpProxy,omitempty"`
 	SSL           string `json:"sslProxy,omitempty"`
@@ -122,8 +131,13 @@ type Proxy struct {
 	SOCKSPassword string `json:"socksPassword,omitempty"`
 	NoProxy       string `json:"noProxy,omitempty"`
 
-	// TODO(minusnine): The W3C draft spec includes port fields as well. Should
-	// they be added here?
+	// The W3C draft spec includes port fields as well. According to the
+	// specification, ports can also be included in the above addresses. However,
+	// in the Geckodriver implementation, the ports must be specified by these
+	// additional fields.
+	HTTPPort  int `json:"httpProxyPort,omitempty"`
+	SSLPort   int `json:"sslProxyPort,omitempty"`
+	SocksPort int `json:"socksProxyPort,omitempty"`
 }
 
 // ProxyType is an enumeration of the types of proxies available.

vendor/init.go

@@ -64,9 +64,9 @@ var files = []file{
 	},
 	{
 		// This is a recent nightly. Update this path periodically.
-		url:     "https://archive.mozilla.org/pub/firefox/nightly/2017/02/2017-02-14-11-02-12-mozilla-central/firefox-54.0a1.en-US.linux-x86_64.tar.bz2",
+		url:     "https://archive.mozilla.org/pub/firefox/nightly/2017/02/2017-02-15-11-01-51-mozilla-central/firefox-54.0a1.en-US.linux-x86_64.tar.bz2",
 		name:    "firefox-54.0a1.en-US.linux-x86_64.tar.bz2",
-		hash:    "df3dcecbb630ca662851160b4d619a11c3ab52a8ceb238eb00e522248a3890ee",
+		hash:    "1d2a066308b9c31adc8fe6f9ce92e6cb503e004141b4ca8b7a50f74632ae7aed",
 		browser: true,
 		rename:  []string{"firefox", "firefox-nightly"},
 	},