Add iossim testing tool for running iOS unit tests.

iossim is a command line tool used to run an iOS app in the iOS Simulator.

BUG=None
TEST=None


Review URL: https://chromiumcodereview.appspot.com/10805004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@148753 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 604 insertions, 0 deletions

diff --git a/testing/iossim/OWNERS b/testing/iossim/OWNERS
new file mode 100644
index 0000000..1b3348e
--- /dev/null
+++ b/testing/iossim/OWNERS
@@ -0,0 +1,2 @@
+rohitrao@chromium.org
+stuartmorgan@chromium.org
diff --git a/testing/iossim/iossim.gyp b/testing/iossim/iossim.gyp
new file mode 100644
index 0000000..ffb4f7d
--- /dev/null
+++ b/testing/iossim/iossim.gyp
@@ -0,0 +1,60 @@
+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+{
+  'variables': {
+    'iphone_sim_path': '$(DEVELOPER_DIR)/Platforms/iPhoneSimulator.platform/Developer/Library/PrivateFrameworks',
+    'other_frameworks_path': '$(DEVELOPER_DIR)/../OtherFrameworks'
+  },
+  'targets': [
+    {
+      'target_name': 'iossim',
+      'type': 'executable',
+      'dependencies': [
+        '<(DEPTH)/testing/iossim/third_party/class-dump/class-dump.gyp:class-dump',
+      ],
+      'include_dirs': [
+        '<(INTERMEDIATE_DIR)/iossim',
+      ],
+      'sources': [
+        'iossim.mm',
+        '<(INTERMEDIATE_DIR)/iossim/iPhoneSimulatorRemoteClient.h',
+      ],
+      'libraries': [
+        '$(SDKROOT)/System/Library/Frameworks/Foundation.framework',
+        '<(iphone_sim_path)/iPhoneSimulatorRemoteClient.framework',
+      ],
+      'mac_framework_dirs': [
+        '<(iphone_sim_path)',
+      ],
+      'xcode_settings': {
+        'LD_RUNPATH_SEARCH_PATHS': [
+          '<(iphone_sim_path)',
+          '<(other_frameworks_path)',
+        ]
+      },
+      'actions': [
+        {
+          'action_name': 'generate_iphone_sim_header',
+          'inputs': [
+            '<(iphone_sim_path)/iPhoneSimulatorRemoteClient.framework/Versions/Current/iPhoneSimulatorRemoteClient',
+            '$(BUILD_DIR)/$(CONFIGURATION)/class-dump',
+          ],
+          'outputs': [
+            '<(INTERMEDIATE_DIR)/iossim/iPhoneSimulatorRemoteClient.h'
+          ],
+          'action': [
+            # Actions don't provide a way to redirect stdout, so a custom
+            # script is invoked that will execute the first argument and write
+            # the output to the file specified as the second argument.
+            '<(DEPTH)/testing/iossim/RedirectStdout.sh',
+            '$(BUILD_DIR)/$(CONFIGURATION)/class-dump -CiPhoneSimulator <(iphone_sim_path)/iPhoneSimulatorRemoteClient.framework',
+            '<(INTERMEDIATE_DIR)/iossim/iPhoneSimulatorRemoteClient.h',
+          ],
+          'message': 'Generating header',
+        },
+      ],
+    },
+  ],
+}
diff --git a/testing/iossim/iossim.mm b/testing/iossim/iossim.mm
new file mode 100644
index 0000000..50b50a3
--- /dev/null
+++ b/testing/iossim/iossim.mm
@@ -0,0 +1,522 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import <Foundation/Foundation.h>
+#include <asl.h>
+#include <libgen.h>
+#include <stdarg.h>
+#include <stdio.h>
+
+// An executable (iossim) that runs an app in the iOS Simulator.
+// Run 'iossim -h' for usage information.
+//
+// For best results, the iOS Simulator application should not be running when
+// iossim is invoked.
+//
+// Headers for the iPhoneSimulatorRemoteClient framework used in this tool are
+// generated by class-dump, via GYP.
+// (class-dump is available at http://www.codethecode.com/projects/class-dump/)
+//
+// However, there are some forward declarations required to get things to
+// compile. Also, the DTiPhoneSimulatorSessionDelegate protocol is referenced
+// by the iPhoneSimulatorRemoteClient framework, but not defined in the object
+// file, so it must be defined here before importing the generated
+// iPhoneSimulatorRemoteClient.h file.
+
+@class DTiPhoneSimulatorApplicationSpecifier;
+@class DTiPhoneSimulatorSession;
+@class DTiPhoneSimulatorSessionConfig;
+@class DTiPhoneSimulatorSystemRoot;
+
+@protocol DTiPhoneSimulatorSessionDelegate
+- (void)session:(DTiPhoneSimulatorSession*)session
+    didEndWithError:(NSError*)error;
+- (void)session:(DTiPhoneSimulatorSession*)session
+       didStart:(BOOL)started
+      withError:(NSError*)error;
+@end
+
+#import "iPhoneSimulatorRemoteClient.h"
+
+// An undocumented system log key included in messages from launchd. The value
+// is the PID of the process the message is about (as opposed to launchd's PID).
+#define ASL_KEY_REF_PID "RefPID"
+
+namespace {
+
+// Name of environment variables that control the user's home directory in the
+// simulator.
+const char* const kUserHomeEnvVariable = "CFFIXED_USER_HOME";
+const char* const kHomeEnvVariable = "HOME";
+
+// Device family codes for iPhone and iPad.
+const int kIPhoneFamily = 1;
+const int kIPadFamily = 2;
+
+// Max number of seconds to wait for the simulator session to start.
+// This timeout must allow time to start up iOS Simulator, install the app
+// and perform any other black magic that is encoded in the
+// iPhoneSimulatorRemoteClient framework to kick things off. Normal start up
+// time is only a couple seconds but machine load, disk caches, etc., can all
+// affect startup time in the wild so the timeout needs to be fairly generous.
+// If this timeout occurs iossim will likely exit with non-zero status; the
+// exception being if the app is invoked and completes execution before the
+// session is started (this case is handled in session:didStart:withError).
+const NSTimeInterval kSessionStartTimeoutSeconds = 30;
+
+// While the simulated app is running, its stdout is redirected to a file which
+// is polled by iossim and written to iossim's stdout using the following
+// polling interval.
+const NSTimeInterval kOutputPollIntervalSeconds = 0.1;
+
+const char* gToolName = "iossim";
+
+void LogError(NSString* format, ...) {
+  va_list list;
+  va_start(list, format);
+
+  NSString* message =
+      [[[NSString alloc] initWithFormat:format arguments:list] autorelease];
+
+  fprintf(stderr, "%s: ERROR: %s\n", gToolName, [message UTF8String]);
+  fflush(stderr);
+
+  va_end(list);
+}
+
+void LogWarning(NSString* format, ...) {
+  va_list list;
+  va_start(list, format);
+
+  NSString* message =
+      [[[NSString alloc] initWithFormat:format arguments:list] autorelease];
+
+  fprintf(stderr, "%s: WARNING: %s\n", gToolName, [message UTF8String]);
+  fflush(stderr);
+
+  va_end(list);
+}
+
+}  // namespace
+
+// A delegate that is called when the simulated app is started or ended in the
+// simulator.
+@interface SimulatorDelegate : NSObject <DTiPhoneSimulatorSessionDelegate> {
+ @private
+  NSString* stdioPath_;  // weak
+  NSThread* outputThread_;
+  BOOL appRunning_;
+}
+@end
+
+// An implementation that copies the simulated app's stdio to stdout of this
+// executable. While it would be nice to get stdout and stderr independently
+// from iOS Simulator, issues like I/O buffering and interleaved output
+// between iOS Simulator and the app would cause iossim to display things out
+// of order here. Printing all output to a single file keeps the order correct.
+// Instances of this classe should be initialized with the location of the
+// simulated app's output file. When the simulated app starts, a thread is
+// started which handles copying data from the simulated app's output file to
+// the stdout of this executable.
+@implementation SimulatorDelegate
+
+// Specifies the file locations of the simulated app's stdout and stderr.
+- (SimulatorDelegate*)initWithStdioPath:(NSString*)stdioPath {
+  self = [super init];
+  if (self)
+    stdioPath_ = [stdioPath copy];
+
+  return self;
+}
+
+- (void)dealloc {
+  [stdioPath_ release];
+  [super dealloc];
+}
+
+// Reads data from the simulated app's output and writes it to stdout. This
+// method blocks, so it should be called in a separate thread. The iOS
+// Simulator takes a file path for the simulated app's stdout and stderr, but
+// this path isn't always available (e.g. when the stdout is Xcode's build
+// window). As a workaround, iossim creates a temp file to hold output, which
+// this method reads and copies to stdout.
+- (void)tailOutput {
+  NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
+
+  // Copy data to stdout/stderr while the app is running.
+  NSFileHandle* simio = [NSFileHandle fileHandleForReadingAtPath:stdioPath_];
+  NSFileHandle* standardOutput = [NSFileHandle fileHandleWithStandardOutput];
+  while (appRunning_) {
+    NSAutoreleasePool* innerPool = [[NSAutoreleasePool alloc] init];
+    [standardOutput writeData:[simio readDataToEndOfFile]];
+    [NSThread sleepForTimeInterval:kOutputPollIntervalSeconds];
+    [innerPool drain];
+  }
+
+  // Once the app is no longer running, copy any data that was written during
+  // the last sleep cycle.
+  [standardOutput writeData:[simio readDataToEndOfFile]];
+
+  [pool drain];
+}
+
+- (void)session:(DTiPhoneSimulatorSession*)session
+       didStart:(BOOL)started
+      withError:(NSError*)error {
+  if (!started) {
+    // If the test executes very quickly (<30ms), the SimulatorDelegate may not
+    // get the initial session:started:withError: message indicating successful
+    // startup of the simulated app. Instead the delegate will get a
+    // session:started:withError: message after the timeout has elapsed. To
+    // account for this case, check if the simulated app's stdio file was
+    // ever created and if it exists dump it to stdout and return success.
+    NSFileManager* fileManager = [NSFileManager defaultManager];
+    if ([fileManager fileExistsAtPath:stdioPath_ isDirectory:NO]) {
+      appRunning_ = NO;
+      [self tailOutput];
+      // Note that exiting in this state leaves a process running
+      // (e.g. /.../iPhoneSimulator4.3.sdk/usr/libexec/installd -t 30) that will
+      // prevent future simulator sessions from being started for 30 seconds
+      // unless the iOS Simulator application is killed altogether.
+      [self session:session didEndWithError:nil];
+
+      // session:didEndWithError should not return (because it exits) so
+      // the execution path should never get here.
+      exit(EXIT_FAILURE);
+    }
+
+    LogError(@"Simulator failed to start: %@", [error localizedDescription]);
+    exit(EXIT_FAILURE);
+  }
+
+  // Start a thread to write contents of outputPath to stdout.
+  appRunning_ = YES;
+  outputThread_ = [[NSThread alloc] initWithTarget:self
+                                          selector:@selector(tailOutput)
+                                            object:nil];
+  [outputThread_ start];
+}
+
+- (void)session:(DTiPhoneSimulatorSession*)session
+    didEndWithError:(NSError*)error {
+  appRunning_ = NO;
+  // Wait for the output thread to finish copying data to stdout.
+  if (outputThread_) {
+    while (![outputThread_ isFinished]) {
+      [NSThread sleepForTimeInterval:kOutputPollIntervalSeconds];
+    }
+    [outputThread_ release];
+    outputThread_ = nil;
+  }
+
+  if (error) {
+    LogError(@"Simulator ended with error: %@", [error localizedDescription]);
+    exit(EXIT_FAILURE);
+  }
+
+  // Check if the simulated app exited abnormally by looking for system log
+  // messages from launchd that refer to the simulated app's PID. Limit query
+  // to messages in the last minute since PIDs are cyclical.
+  aslmsg query = asl_new(ASL_TYPE_QUERY);
+  asl_set_query(query, ASL_KEY_SENDER, "launchd",
+                ASL_QUERY_OP_EQUAL | ASL_QUERY_OP_SUBSTRING);
+  asl_set_query(query, ASL_KEY_REF_PID,
+                [[[session simulatedApplicationPID] stringValue] UTF8String],
+                ASL_QUERY_OP_EQUAL);
+  asl_set_query(query, ASL_KEY_TIME, "-1m", ASL_QUERY_OP_GREATER_EQUAL);
+
+  // Log any messages found.
+  aslresponse response = asl_search(NULL, query);
+  BOOL entryFound = NO;
+  aslmsg entry;
+  while ((entry = aslresponse_next(response)) != NULL) {
+    entryFound = YES;
+    LogWarning(@"Console message: %s", asl_get(entry, ASL_KEY_MSG));
+  }
+
+  // launchd only sends messages if the process crashed or exits with a
+  // non-zero status, so if the query returned any results iossim should exit
+  // with non-zero status.
+  if (entryFound) {
+    LogError(@"Simulated app crashed or exited with non-zero status");
+    exit(EXIT_FAILURE);
+  }
+  exit(EXIT_SUCCESS);
+}
+@end
+
+namespace {
+
+// Converts the given app path to an application spec, which requires an
+// absolute path.
+DTiPhoneSimulatorApplicationSpecifier* BuildAppSpec(NSString* appPath) {
+  if (![appPath isAbsolutePath]) {
+    NSString* cwd = [[NSFileManager defaultManager] currentDirectoryPath];
+    appPath = [cwd stringByAppendingPathComponent:appPath];
+  }
+  appPath = [appPath stringByStandardizingPath];
+  return [DTiPhoneSimulatorApplicationSpecifier
+      specifierWithApplicationPath:appPath];
+}
+
+// Returns the system root for the given SDK version. If sdkVersion is nil, the
+// default system root is returned.  Will return nil if the sdkVersion is not
+// valid.
+DTiPhoneSimulatorSystemRoot* BuildSystemRoot(NSString* sdkVersion) {
+  DTiPhoneSimulatorSystemRoot* systemRoot =
+      [DTiPhoneSimulatorSystemRoot defaultRoot];
+  if (sdkVersion)
+    systemRoot = [DTiPhoneSimulatorSystemRoot rootWithSDKVersion:sdkVersion];
+
+  return systemRoot;
+}
+
+// Builds a config object for starting the specified app.
+DTiPhoneSimulatorSessionConfig* BuildSessionConfig(
+    DTiPhoneSimulatorApplicationSpecifier* appSpec,
+    DTiPhoneSimulatorSystemRoot* systemRoot,
+    NSString* stdoutPath,
+    NSString* stderrPath,
+    NSArray* appArgs,
+    NSNumber* deviceFamily) {
+  DTiPhoneSimulatorSessionConfig* sessionConfig =
+      [[[DTiPhoneSimulatorSessionConfig alloc] init] autorelease];
+  sessionConfig.applicationToSimulateOnStart = appSpec;
+  sessionConfig.simulatedSystemRoot = systemRoot;
+  sessionConfig.localizedClientName = @"chromium";
+  sessionConfig.simulatedApplicationStdErrPath = stderrPath;
+  sessionConfig.simulatedApplicationStdOutPath = stdoutPath;
+  sessionConfig.simulatedApplicationLaunchArgs = appArgs;
+  // TODO(lliabraa): Add support for providing environment variables/values
+  // for the simulated app's environment. The environment can be set using:
+  // sessionConfig.simulatedApplicationLaunchEnvironment =
+  //     [NSDictionary dictionary];
+  sessionConfig.simulatedDeviceFamily = deviceFamily;
+  return sessionConfig;
+}
+
+// Builds a simulator session that will use the given delegate.
+DTiPhoneSimulatorSession* BuildSession(SimulatorDelegate* delegate) {
+  DTiPhoneSimulatorSession* session =
+      [[[DTiPhoneSimulatorSession alloc] init] autorelease];
+  session.delegate = delegate;
+  return session;
+}
+
+// Creates a temporary directory with a unique name based on the provided
+// template. The template should not contain any path separators and be suffixed
+// with X's, which will be substituted with a unique alphanumeric string (see
+// 'man mkdtemp' for details). The directory will be created as a subdirectory
+// of NSTemporaryDirectory(). For example, if dirNameTemplate is 'test-XXX',
+// this method would return something like '/path/to/tempdir/test-3n2'.
+//
+// Returns the absolute path of the newly-created directory, or nill if unable
+// to create a unique directory.
+NSString* CreateTempDirectory(NSString* dirNameTemplate) {
+  NSString* fullPathTemplate =
+      [NSTemporaryDirectory() stringByAppendingPathComponent:dirNameTemplate];
+  char* fullPath = mkdtemp(const_cast<char*>([fullPathTemplate UTF8String]));
+  if (fullPath == NULL)
+    return nil;
+
+  return [NSString stringWithUTF8String:fullPath];
+}
+
+// Creates the necessary directory structure under the given user home directory
+// path.
+// Returns YES if successful, NO if unable to create the directories.
+BOOL CreateHomeDirSubDirs(NSString* userHomePath) {
+  NSFileManager* fileManager = [NSFileManager defaultManager];
+
+  // Create user home and subdirectories.
+  NSArray* subDirsToCreate = [NSArray arrayWithObjects:
+                              @"Documents",
+                              @"Library/Caches",
+                              nil];
+  for (NSString* subDir in subDirsToCreate) {
+    NSString* path = [userHomePath stringByAppendingPathComponent:subDir];
+    NSError* error;
+    if (![fileManager createDirectoryAtPath:path
+                withIntermediateDirectories:YES
+                                 attributes:nil
+                                      error:&error]) {
+      LogError(@"Unable to create directory: %@. Error: %@",
+               path, [error localizedDescription]);
+      return NO;
+    }
+  }
+
+  return YES;
+}
+
+// Creates the necessary directory structure under the given user home directory
+// path, then sets the path in the appropriate environment variable.
+// Returns YES if successful, NO if unable to create or initialize the given
+// directory.
+BOOL InitializeSimulatorUserHome(NSString* userHomePath) {
+  if (!CreateHomeDirSubDirs(userHomePath))
+    return NO;
+
+  // Update the environment to use the specified directory as the user home
+  // directory.
+  // Note: the third param of setenv specifies whether or not to overwrite the
+  // variable's value if it has already been set.
+  if ((setenv(kUserHomeEnvVariable, [userHomePath UTF8String], YES) == -1) ||
+      (setenv(kHomeEnvVariable, [userHomePath UTF8String], YES) == -1)) {
+    LogError(@"Unable to set environment variables for home directory.");
+    return NO;
+  }
+
+  return YES;
+}
+
+// Prints the usage information to stderr.
+void PrintUsage() {
+  fprintf(stderr, "Usage: iossim [-d device] [-s sdkVersion] [-u homeDir] "
+      "<appPath> [<appArgs>]\n"
+      "  where <appPath> is the path to the .app directory and appArgs are any"
+      " arguments to send the simulated app.\n"
+      "\n"
+      "Options:\n"
+      "  -d  Specifies the device (either 'iPhone' or 'iPad')."
+      " Defaults to 'iPhone'.\n"
+      "  -s  Specifies the SDK version to use (e.g '4.3')."
+      " Will use system default if not specified.\n"
+      "  -u  Specifies a user home directory for the simulator."
+      " Will create a new directory if not specified.\n");
+}
+
+}  // namespace
+
+int main(int argc, char* const argv[]) {
+  NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
+
+  char* toolName = basename(argv[0]);
+  if (toolName != NULL)
+    gToolName = toolName;
+
+  NSString* appPath = nil;
+  NSString* appName = nil;
+  NSString* sdkVersion = nil;
+  NSString* deviceName = @"iPhone";
+  NSString* simHomePath = nil;
+  NSMutableArray* appArgs = [NSMutableArray array];
+
+  // Parse the optional arguments
+  int c;
+  while ((c = getopt(argc, argv, "hs:d:u:")) != -1) {
+    switch (c) {
+      case 's':
+        sdkVersion = [NSString stringWithUTF8String:optarg];
+        break;
+      case 'd':
+        deviceName = [NSString stringWithUTF8String:optarg];
+        break;
+      case 'u':
+        simHomePath = [[NSFileManager defaultManager]
+            stringWithFileSystemRepresentation:optarg length:strlen(optarg)];
+        break;
+      case 'h':
+        PrintUsage();
+        exit(EXIT_SUCCESS);
+      default:
+        PrintUsage();
+        exit(EXIT_FAILURE);
+    }
+  }
+
+  // There should be at least one arg left, specifying the app path. Any
+  // additional args are passed as arguments to the app.
+  if (optind < argc) {
+    appPath = [[NSFileManager defaultManager]
+        stringWithFileSystemRepresentation:argv[optind]
+                                    length:strlen(argv[optind])];
+    appName = [appPath lastPathComponent];
+    while (++optind < argc) {
+      [appArgs addObject:[NSString stringWithUTF8String:argv[optind]]];
+    }
+  } else {
+    LogError(@"Unable to parse command line arguments.");
+    PrintUsage();
+    exit(EXIT_FAILURE);
+  }
+
+  // Make sure the app path provided is legit.
+  DTiPhoneSimulatorApplicationSpecifier* appSpec = BuildAppSpec(appPath);
+  if (!appSpec) {
+    LogError(@"Invalid app path: %@", appPath);
+    exit(EXIT_FAILURE);
+  }
+
+  // Make sure the SDK path provided is legit (or nil).
+  DTiPhoneSimulatorSystemRoot* systemRoot = BuildSystemRoot(sdkVersion);
+  if (!systemRoot) {
+    LogError(@"Invalid SDK version: %@", sdkVersion);
+    exit(EXIT_FAILURE);
+  }
+
+  // Get the paths for stdout and stderr so the simulated app's output will show
+  // up in the caller's stdout/stderr.
+  NSString* outputDir = CreateTempDirectory(@"iossim-XXXXXX");
+  NSString* stdioPath = [outputDir stringByAppendingPathComponent:@"stdio.txt"];
+
+  // Make sure the device name is legit.
+  NSNumber* deviceFamily = nil;
+  if (!deviceName ||
+      [@"iPhone" caseInsensitiveCompare:deviceName] == NSOrderedSame) {
+    deviceFamily = [NSNumber numberWithInt:kIPhoneFamily];
+  } else if ([@"iPad" caseInsensitiveCompare:deviceName] == NSOrderedSame) {
+    deviceFamily = [NSNumber numberWithInt:kIPadFamily];
+  } else {
+    LogError(@"Invalid device name: %@", deviceName);
+    exit(EXIT_FAILURE);
+  }
+
+  // Set up the user home directory for the simulator
+  if (!simHomePath) {
+    NSString* dirNameTemplate =
+        [NSString stringWithFormat:@"iossim-%@-%@-XXXXXX", appName, deviceName];
+    simHomePath = CreateTempDirectory(dirNameTemplate);
+    if (!simHomePath) {
+      LogError(@"Unable to create unique directory for template %@",
+               dirNameTemplate);
+      exit(EXIT_FAILURE);
+    }
+  }
+  if (!InitializeSimulatorUserHome(simHomePath)) {
+    LogError(@"Unable to initialize home directory for simulator: %@",
+             simHomePath);
+    exit(EXIT_FAILURE);
+  }
+
+  // Create the config and simulator session.
+  DTiPhoneSimulatorSessionConfig* config = BuildSessionConfig(appSpec,
+                                                              systemRoot,
+                                                              stdioPath,
+                                                              stdioPath,
+                                                              appArgs,
+                                                              deviceFamily);
+  SimulatorDelegate* delegate =
+  [[[SimulatorDelegate alloc] initWithStdioPath:stdioPath] autorelease];
+  DTiPhoneSimulatorSession* session = BuildSession(delegate);
+
+  // Start the simulator session.
+  NSError* error;
+  BOOL started = [session requestStartWithConfig:config
+                                         timeout:kSessionStartTimeoutSeconds
+                                           error:&error];
+
+  // Spin the runtime indefinitely. When the delegate gets the message that the
+  // app has quit it will exit this program.
+  if (started)
+    [[NSRunLoop mainRunLoop] run];
+  else
+    LogError(@"Simulator failed to start: %@", [error localizedDescription]);
+
+  // Note that this code is only executed if the simulator fails to start
+  // because once the main run loop is started, only the delegate calling
+  // exit() will end the program.
+  [pool drain];
+  return EXIT_FAILURE;
+}
diff --git a/testing/iossim/redirect-stdout.sh b/testing/iossim/redirect-stdout.sh
new file mode 100755
index 0000000..feff2c9
--- /dev/null
+++ b/testing/iossim/redirect-stdout.sh
@@ -0,0 +1,20 @@
+#!/bin/sh
+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+#
+# This script executes the command given as the first argument and redirects
+# the command's stdout to the file given as the second argument.
+#
+# Example: Write the text 'foo' to a file called out.txt:
+#   RedirectStdout.sh "echo foo" out.txt
+#
+# This script is invoked from iossim.gyp in order to redirect the output of
+# class-dump to a file (because gyp actions don't support redirecting output).
+
+if [ ${#} -ne 2 ] ; then
+  echo "usage: ${0} <command> <output file>"
+  exit 2
+fi
+
+exec $1 > $2
\ No newline at end of file