如何搭建并定制 WebDriverAgent Server
Appium 的 iOS 版本的后端用的是Facebook's WebDriverAgent。该后端是基于苹果公司的 XCTest 框架，所以也有所有XCTest 框架已知的问题。其中有些问题我们正在设法解决，有一些在现阶段可能无法解决。本文中描述的方法已经能够使您完全掌握在设备上如何构建、管理和运行WDA。通过这种方式，您可以在CI环境中对您的自动化测试进行微调，并使其在长期运行的情况下更加稳定。
重点： * 如果使用了Appium的默认设置，则不需要如下的步骤。服务器将为您搞定一切，当然你也不能对WDA做太多控制。 * 对连接的被测设备必须有SSH或物理访问权限。
安装WDA
Appium 会自动下载 WebDriverAgent 源码。如果使用 npm 命令（npm install -g appium） 安装Appium的话，通常情况下会保存在/usr/local/lib/node_modules/appium/node_modules/appium-xcuitest-driver/WebDriverAgent 目录下。
如果是首次安装的话，还需要下载一些第三方依赖("carthage"工具就是为此准备的: brew install carthage):
cd /usr/local/lib/node_modules/appium/node_modules/appium-xcuitest-driver/WebDriverAgent
./Scripts/bootstrap.sh -d
不需要进一步的配置步骤，你就可以在iOS模拟器上执行自动化测试。
如果是在真机上进行测试的话，则需要做更多的设置。参考real device configuration documentation 设置代码签名。另外，你还需要安装iproxy工具。
npm install -g iproxy
为了确保 WDA 源代码配置正确，请执行以下操作：
- 用Xcode打开/usr/local/lib/node_modules/appium/node_modules/appium-xcuitest-driver/WebDriverAgent/WebDriverAgent.xcodeproj
- 选择 "WebDriverAgentRunner" 工程
- 选择要运行自动化测试的真机/模拟器作为构建目标机
- 在主菜单中选择 Product -> Test
Xcode 会成功构建项目并安装到真机/模拟器上，所以您将在苹果系统的桌面上看到 WebDriverAgentRunner 应用程序的图标。
启动WDA
WebDriverAgent 应用程序扮演一个 REST 服务的角色，接收外部 API 请求，然后传递给被测应用的原生 XCTest 调用。如果在模拟器上运行你的测试，REST 服务的地址将是localhost，如果在有实际的 IP 地址的真实设备上运行，REST 服务的地址将是实际的 ip 地址。我们使用 iproxy 将网络请求路由到通过 USB 连接的真实设备上，这意味着可以使用这个工具将模拟器和真实设备上的 WDA 网络地址统一。
这个用Java编写的助手类说明了主要的实现细节：
public class WDAServer {
private static final Logger log = ZLogger.getLog(WDAServer.class.getSimpleName());
private static final int MAX_REAL_DEVICE_RESTART_RETRIES = 1;
private static final Timedelta REAL_DEVICE_RUNNING_TIMEOUT = Timedelta.ofMinutes(4);
private static final Timedelta RESTART_TIMEOUT = Timedelta.ofMinutes(1);
// These settings are needed to properly sign WDA for real device tests
// See https://github.com/appium/appium-xcuitest-driver for more details
private static final File KEYCHAIN = new File(String.format("%s/%s",
System.getProperty("user.home"), "/Library/Keychains/MyKeychain.keychain"));
private static final String KEYCHAIN_PASSWORD = "******";
private static final File IPROXY_EXECUTABLE = new File("/usr/local/bin/iproxy");
private static final File XCODEBUILD_EXECUTABLE = new File("/usr/bin/xcodebuild");
private static final File WDA_PROJECT =
new File("/usr/local/lib/node_modules/appium/node_modules/appium-xcuitest-driver/" +
"WebDriverAgent/WebDriverAgent.xcodeproj");
private static final String WDA_SCHEME = "WebDriverAgentRunner";
private static final String WDA_CONFIGURATION = "Debug";
private static final File XCODEBUILD_LOG = new File("/usr/local/var/log/appium/build.log");
private static final File IPROXY_LOG = new File("/usr/local/var/log/appium/iproxy.log");
private static final int PORT = 8100;
public static final String SERVER_URL = String.format("http://127.0.0.1:%d", PORT);
private static final String[] IPROXY_CMDLINE = new String[]{
IPROXY_EXECUTABLE.getAbsolutePath(),
Integer.toString(PORT),
Integer.toString(PORT),
String.format("> %s 2>&1 &", IPROXY_LOG.getAbsolutePath())
};
private static WDAServer instance = null;
private final boolean isRealDevice;
private final String deviceId;
private final String platformVersion;
private int failedRestartRetriesCount = 0;
private WDAServer() {
try {
this.isRealDevice = !getIsSimulatorFromConfig(getClass());
final String udid;
if (isRealDevice) {
udid = IOSRealDeviceHelpers.getUDID();
} else {
udid = IOSSimulatorHelpers.getId();
}
this.deviceId = udid;
this.platformVersion = getPlatformVersionFromConfig(getClass());
} catch (Exception e) {
throw new RuntimeException(e);
}
ensureToolsExistence();
ensureParentDirExistence();
}
public synchronized static WDAServer getInstance() {
if (instance == null) {
instance = new WDAServer();
}
return instance;
}
private boolean waitUntilIsRunning(Timedelta timeout) throws Exception {
final URL status = new URL(SERVER_URL + "/status");
try {
if (timeout.asSeconds() > 5) {
log.debug(String.format("Waiting max %s until WDA server starts responding...", timeout));
}
new UrlChecker().waitUntilAvailable(timeout.asMillis(), TimeUnit.MILLISECONDS, status);
return true;
} catch (UrlChecker.TimeoutException e) {
return false;
}
}
private static void ensureParentDirExistence() {
if (!XCODEBUILD_LOG.getParentFile().exists()) {
if (!XCODEBUILD_LOG.getParentFile().mkdirs()) {
throw new IllegalStateException(String.format(
"The script has failed to create '%s' folder for Appium logs. " +
"Please make sure your account has correct access permissions on the parent folder(s)",
XCODEBUILD_LOG.getParentFile().getAbsolutePath()));
}
}
}
private void ensureToolsExistence() {
if (isRealDevice && !IPROXY_EXECUTABLE.exists()) {
throw new IllegalStateException(String.format("%s tool is expected to be installed (`npm install -g iproxy`)",
IPROXY_EXECUTABLE.getAbsolutePath()));
}
if (!XCODEBUILD_EXECUTABLE.exists()) {
throw new IllegalStateException(String.format("xcodebuild tool is not detected on the current system at %s",
XCODEBUILD_EXECUTABLE.getAbsolutePath()));
}
if (!WDA_PROJECT.exists()) {
throw new IllegalStateException(String.format("WDA project is expected to exist at %s",
WDA_PROJECT.getAbsolutePath()));
}
}
private List<String> generateXcodebuildCmdline() {
final List<String> result = new ArrayList<>();
result.add(XCODEBUILD_EXECUTABLE.getAbsolutePath());
result.add("clean build test");
result.add(String.format("-project %s", WDA_PROJECT.getAbsolutePath()));
result.add(String.format("-scheme %s", WDA_SCHEME));
result.add(String.format("-destination id=%s", deviceId));
result.add(String.format("-configuration %s", WDA_CONFIGURATION));
result.add(String.format("IPHONEOS_DEPLOYMENT_TARGET=%s", platformVersion));
result.add(String.format("> %s 2>&1 &", XCODEBUILD_LOG.getAbsolutePath()));
return result;
}
private static List<String> generateKeychainUnlockCmdlines() throws Exception {
final List<String> result = new ArrayList<>();
result.add(String.format("/usr/bin/security -v list-keychains -s %s", KEYCHAIN.getAbsolutePath()));
result.add(String.format("/usr/bin/security -v unlock-keychain -p %s %s",
KEYCHAIN_PASSWORD, KEYCHAIN.getAbsolutePath()));
result.add(String.format("/usr/bin/security set-keychain-settings -t 3600 %s", KEYCHAIN.getAbsolutePath()));
return result;
}
public synchronized void restart() throws Exception {
if (isRealDevice && failedRestartRetriesCount >= MAX_REAL_DEVICE_RESTART_RETRIES) {
throw new IllegalStateException(String.format(
"WDA server cannot start on the connected device with udid %s after %s retries. " +
"Reboot the device manually and try again", deviceId, MAX_REAL_DEVICE_RESTART_RETRIES));
}
final String hostname = InetAddress.getLocalHost().getHostName();
log.info(String.format("Trying to (re)start WDA server on %s:%s...", hostname, PORT));
UnixProcessHelpers.killProcessesGracefully(IPROXY_EXECUTABLE.getName(), XCODEBUILD_EXECUTABLE.getName());
final File scriptFile = File.createTempFile("script", ".sh");
try {
final List<String> scriptContent = new ArrayList<>();
scriptContent.add("#!/bin/bash");
if (isRealDevice && isRunningInJenkinsNetwork()) {
scriptContent.add(String.join("\n", generateKeychainUnlockCmdlines()));
}
if (isRealDevice) {
scriptContent.add(String.join(" ", IPROXY_CMDLINE));
}
final String wdaBuildCmdline = String.join(" ", generateXcodebuildCmdline());
log.debug(String.format("Building WDA with command line:\n%s\n", wdaBuildCmdline));
scriptContent.add(wdaBuildCmdline);
try (Writer output = new BufferedWriter(new FileWriter(scriptFile))) {
output.write(String.join("\n", scriptContent));
}
new ProcessBuilder("/bin/chmod", "u+x", scriptFile.getCanonicalPath())
.redirectErrorStream(true).start().waitFor(5, TimeUnit.SECONDS);
final ProcessBuilder pb = new ProcessBuilder("/bin/bash", scriptFile.getCanonicalPath());
final Map<String, String> env = pb.environment();
// This is needed for Jenkins
env.put("BUILD_ID", "dontKillMe");
log.info(String.format("Waiting max %s for WDA to be (re)started on %s:%s...", RESTART_TIMEOUT.toString(),
hostname, PORT));
final Timedelta started = Timedelta.now();
pb.redirectErrorStream(true).start().waitFor(RESTART_TIMEOUT.asMillis(), TimeUnit.MILLISECONDS);
if (!waitUntilIsRunning(RESTART_TIMEOUT)) {
++failedRestartRetriesCount;
throw new IllegalStateException(
String.format("WDA server has failed to start after %s timeout on server '%s'.\n"
+ "Please make sure that iDevice is properly connected and you can build "
+ "WDA manually from XCode.\n"
+ "Xcodebuild logs:\n\n%s\n\n\niproxy logs:\n\n%s\n\n\n",
RESTART_TIMEOUT, hostname,
getLog(XCODEBUILD_LOG).orElse("EMPTY"), getLog(IPROXY_LOG).orElse("EMPTY"))
);
}
log.info(String.format("WDA server has been successfully (re)started after %s " +
"and now is listening on %s:%s", Timedelta.now().diff(started).toString(), hostname, PORT));
} finally {
scriptFile.delete();
}
}
public boolean isRunning() throws Exception {
if (!isProcessRunning(XCODEBUILD_EXECUTABLE.getName())
|| (isRealDevice && !isProcessRunning(IPROXY_EXECUTABLE.getName()))) {
return false;
}
return waitUntilIsRunning(isRealDevice ? REAL_DEVICE_RUNNING_TIMEOUT : Timedelta.ofSeconds(3));
}
public Optional<String> getLog(File logFile) {
if (logFile.exists()) {
try {
return Optional.of(new String(Files.readAllBytes(logFile.toPath()), Charset.forName("UTF-8")));
} catch (IOException e) {
e.printStackTrace();
}
}
return Optional.empty();
}
public void resetLogs() {
for (File logFile : new File[]{XCODEBUILD_LOG, IPROXY_LOG}) {
if (logFile.exists()) {
try {
final PrintWriter writer = new PrintWriter(logFile);
writer.print("");
writer.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
}
}
}
之前应该调用这段代码来启动 Appium iOS 驱动，例如，在 setUp 方法中：
if (!WDAServer.getInstance().isRunning()) {
WDAServer.getInstance().restart();
}
为 Appium 驱动程序设置 webDriverAgentUrl 非常重要，让它知道我们的 WDA 驱动程序可以使用：
capabilities.setCapability("webDriverAgentUrl", WDAServer.SERVER_URL);
重要注释
- 如果是 jenkins agent 执行的，该进程不能直接访问钥匙串（Keychain），所以我们需要在为真实设备编译 WDA 之前准备钥匙串，否则编码将失败。
- 如果 xcodebuild 和 iproxy 进程已经被冻结，我们在重新启动之前杀死这些进程，以确保编译成功，
- 我们准备一个单独的 bash 脚本并独立于 iproxy / xcodebuild 进程，所以即使在实际的代码执行完成后，它们也可以在后台继续运行。如果在自动化实验室中的同一机器/节点上执行多个测试/套件，最少的人工干预是非常重要的。
- 更改 BUILD_ID 环境变量的值以避免在作业完成后由 Jenkins agent 程序杀死后台进程。
- isRunning 检查是通过验证实际的网络终端来完成的.
- 守护进程的输出会存入日志，因此可以跟踪错误和意外的故障。如果服务器无法启动/重启，日志文件的内容会自动添加到实际的错误消息中。
- 真机设备ID可以从
system_profiler SPUSBDataType输出中解析 - 模拟器ID可以从
xcrun simctl list输出中解析 - UrlChecker 类是从 org.openqa.selenium.net 包导入的
本文由 simple 翻译，由 lihuazhang 校验。