Implements the test sharding protocol. By Eric Fellheimer.

git-svn-id: http://googletest.googlecode.com/svn/trunk@187 861a406c-534a-0410-8894-cb66d6ee9925

10 files changed, 619 insertions, 62 deletions

diff --git a/src/gtest-internal-inl.h b/src/gtest-internal-inl.h
index cefed20..07d0c5b 100644
--- a/src/gtest-internal-inl.h
+++ b/src/gtest-internal-inl.h
@@ -162,6 +162,32 @@ String WideStringToUtf8(const wchar_t* str, int num_chars);
 // Returns the number of active threads, or 0 when there is an error.
 size_t GetThreadCount();
 
+// Reads the GTEST_SHARD_STATUS_FILE environment variable, and creates the file
+// if the variable is present. If a file already exists at this location, this
+// function will write over it. If the variable is present, but the file cannot
+// be created, prints an error and exits.
+void WriteToShardStatusFileIfNeeded();
+
+// Checks whether sharding is enabled by examining the relevant
+// environment variable values. If the variables are present,
+// but inconsistent (e.g., shard_index >= total_shards), prints
+// an error and exits. If in_subprocess_for_death_test, sharding is
+// disabled because it must only be applied to the original test
+// process. Otherwise, we could filter out death tests we intended to execute.
+bool ShouldShard(const char* total_shards_str, const char* shard_index_str,
+                 bool in_subprocess_for_death_test);
+
+// Parses the environment variable var as an Int32. If it is unset,
+// returns default_val. If it is not an Int32, prints an error and
+// and aborts.
+Int32 Int32FromEnvOrDie(const char* env_var, Int32 default_val);
+
+// Given the total number of shards, the shard index, and the test id,
+// returns true iff the test should be run on this shard. The test id is
+// some arbitrary but unique non-negative integer assigned to each test
+// method. Assumes that 0 <= shard_index < total_shards.
+bool ShouldRunTestOnShard(int total_shards, int shard_index, int test_id);
+
 // List is a simple singly-linked list container.
 //
 // We cannot use std::list as Microsoft's implementation of STL has
@@ -1111,11 +1137,18 @@ class UnitTestImpl {
     ad_hoc_test_result_.Clear();
   }
 
+  enum ReactionToSharding {
+    HONOR_SHARDING_PROTOCOL,
+    IGNORE_SHARDING_PROTOCOL
+  };
+
   // Matches the full name of each test against the user-specified
   // filter to decide whether the test should run, then records the
   // result in each TestCase and TestInfo object.
+  // If shard_tests == HONOR_SHARDING_PROTOCOL, further filters tests
+  // based on sharding variables in the environment.
   // Returns the number of tests that should run.
-  int FilterTests();
+  int FilterTests(ReactionToSharding shard_tests);
 
   // Lists all the tests by name.
   void ListAllTests();
diff --git a/src/gtest-port.cc b/src/gtest-port.cc
index 3c9ec4b..9348f55 100644
--- a/src/gtest-port.cc
+++ b/src/gtest-port.cc
@@ -512,17 +512,6 @@ static String FlagToEnvVar(const char* flag) {
   return env_var.GetString();
 }
 
-// Reads and returns the Boolean environment variable corresponding to
-// the given flag; if it's not set, returns default_value.
-//
-// The value is considered true iff it's not "0".
-bool BoolFromGTestEnv(const char* flag, bool default_value) {
-  const String env_var = FlagToEnvVar(flag);
-  const char* const string_value = GetEnv(env_var.c_str());
-  return string_value == NULL ?
-      default_value : strcmp(string_value, "0") != 0;
-}
-
 // Parses 'str' for a 32-bit signed integer.  If successful, writes
 // the result to *value and returns true; otherwise leaves *value
 // unchanged and returns false.
@@ -564,6 +553,17 @@ bool ParseInt32(const Message& src_text, const char* str, Int32* value) {
   return true;
 }
 
+// Reads and returns the Boolean environment variable corresponding to
+// the given flag; if it's not set, returns default_value.
+//
+// The value is considered true iff it's not "0".
+bool BoolFromGTestEnv(const char* flag, bool default_value) {
+  const String env_var = FlagToEnvVar(flag);
+  const char* const string_value = GetEnv(env_var.c_str());
+  return string_value == NULL ?
+      default_value : strcmp(string_value, "0") != 0;
+}
+
 // Reads and returns a 32-bit integer stored in the environment
 // variable corresponding to the given flag; if it isn't set or
 // doesn't represent a valid 32-bit integer, returns default_value.
diff --git a/src/gtest.cc b/src/gtest.cc
index 8e8238a..0d161e0 100644
--- a/src/gtest.cc
+++ b/src/gtest.cc
@@ -145,6 +145,13 @@ static const char kUniversalFilter[] = "*";
 // The default output file for XML output.
 static const char kDefaultOutputFile[] = "test_detail.xml";
 
+// The environment variable name for the test shard index.
+static const char kTestShardIndex[] = "GTEST_SHARD_INDEX";
+// The environment variable name for the total number of test shards.
+static const char kTestTotalShards[] = "GTEST_TOTAL_SHARDS";
+// The environment variable name for the test shard status file.
+static const char kTestShardStatusFile[] = "GTEST_SHARD_STATUS_FILE";
+
 namespace internal {
 
 // The text used in failure messages to indicate the start of the
@@ -2595,6 +2602,13 @@ void PrettyUnitTestResultPrinter::OnUnitTestStart(
                   "Note: %s filter = %s\n", GTEST_NAME, filter);
   }
 
+  if (internal::ShouldShard(kTestTotalShards, kTestShardIndex, false)) {
+    ColoredPrintf(COLOR_YELLOW,
+                  "Note: This is test shard %s of %s.\n",
+                  internal::GetEnv(kTestShardIndex),
+                  internal::GetEnv(kTestTotalShards));
+  }
+
   const internal::UnitTestImpl* const impl = unit_test->impl();
   ColoredPrintf(COLOR_GREEN,  "[==========] ");
   printf("Running %s from %s.\n",
@@ -3510,6 +3524,11 @@ int UnitTestImpl::RunAllTests() {
 
   RegisterParameterizedTests();
 
+  // Even if sharding is not on, test runners may want to use the
+  // GTEST_SHARD_STATUS_FILE to query whether the test supports the sharding
+  // protocol.
+  internal::WriteToShardStatusFileIfNeeded();
+
   // Lists all the tests and exits if the --gtest_list_tests
   // flag was specified.
   if (GTEST_FLAG(list_tests)) {
@@ -3528,9 +3547,15 @@ int UnitTestImpl::RunAllTests() {
 
   UnitTestEventListenerInterface * const printer = result_printer();
 
+  const bool should_shard = ShouldShard(kTestTotalShards, kTestShardIndex,
+                                        in_subprocess_for_death_test);
+
   // Compares the full test names with the filter to decide which
   // tests to run.
-  const bool has_tests_to_run = FilterTests() > 0;
+  const bool has_tests_to_run = FilterTests(should_shard
+                                              ? HONOR_SHARDING_PROTOCOL
+                                              : IGNORE_SHARDING_PROTOCOL) > 0;
+
   // True iff at least one test has failed.
   bool failed = false;
 
@@ -3586,12 +3611,126 @@ int UnitTestImpl::RunAllTests() {
   return failed ? 1 : 0;
 }
 
+// Reads the GTEST_SHARD_STATUS_FILE environment variable, and creates the file
+// if the variable is present. If a file already exists at this location, this
+// function will write over it. If the variable is present, but the file cannot
+// be created, prints an error and exits.
+void WriteToShardStatusFileIfNeeded() {
+  const char* const test_shard_file = GetEnv(kTestShardStatusFile);
+  if (test_shard_file != NULL) {
+#ifdef _MSC_VER  // MSVC 8 deprecates fopen().
+#pragma warning(push)          // Saves the current warning state.
+#pragma warning(disable:4996)  // Temporarily disables warning on
+                               // deprecated functions.
+#endif
+    FILE* const file = fopen(test_shard_file, "w");
+#ifdef _MSC_VER
+#pragma warning(pop)           // Restores the warning state.
+#endif
+    if (file == NULL) {
+      ColoredPrintf(COLOR_RED,
+                    "Could not write to the test shard status file \"%s\" "
+                    "specified by the %s environment variable.\n",
+                    test_shard_file, kTestShardStatusFile);
+      fflush(stdout);
+      exit(EXIT_FAILURE);
+    }
+    fclose(file);
+  }
+}
+
+// Checks whether sharding is enabled by examining the relevant
+// environment variable values. If the variables are present,
+// but inconsistent (i.e., shard_index >= total_shards), prints
+// an error and exits. If in_subprocess_for_death_test, sharding is
+// disabled because it must only be applied to the original test
+// process. Otherwise, we could filter out death tests we intended to execute.
+bool ShouldShard(const char* total_shards_env,
+                 const char* shard_index_env,
+                 bool in_subprocess_for_death_test) {
+  if (in_subprocess_for_death_test) {
+    return false;
+  }
+
+  const Int32 total_shards = Int32FromEnvOrDie(total_shards_env, -1);
+  const Int32 shard_index = Int32FromEnvOrDie(shard_index_env, -1);
+
+  if (total_shards == -1 && shard_index == -1) {
+    return false;
+  } else if (total_shards == -1 && shard_index != -1) {
+    const Message msg = Message()
+      << "Invalid environment variables: you have "
+      << kTestShardIndex << " = " << shard_index
+      << ", but have left " << kTestTotalShards << " unset.\n";
+    ColoredPrintf(COLOR_RED, msg.GetString().c_str());
+    fflush(stdout);
+    exit(EXIT_FAILURE);
+  } else if (total_shards != -1 && shard_index == -1) {
+    const Message msg = Message()
+      << "Invalid environment variables: you have "
+      << kTestTotalShards << " = " << total_shards
+      << ", but have left " << kTestShardIndex << " unset.\n";
+    ColoredPrintf(COLOR_RED, msg.GetString().c_str());
+    fflush(stdout);
+    exit(EXIT_FAILURE);
+  } else if (shard_index < 0 || shard_index >= total_shards) {
+    const Message msg = Message()
+      << "Invalid environment variables: we require 0 <= "
+      << kTestShardIndex << " < " << kTestTotalShards
+      << ", but you have " << kTestShardIndex << "=" << shard_index
+      << ", " << kTestTotalShards << "=" << total_shards << ".\n";
+    ColoredPrintf(COLOR_RED, msg.GetString().c_str());
+    fflush(stdout);
+    exit(EXIT_FAILURE);
+  }
+
+  return total_shards > 1;
+}
+
+// Parses the environment variable var as an Int32. If it is unset,
+// returns default_val. If it is not an Int32, prints an error
+// and aborts.
+Int32 Int32FromEnvOrDie(const char* const var, Int32 default_val) {
+  const char* str_val = GetEnv(var);
+  if (str_val == NULL) {
+    return default_val;
+  }
+
+  Int32 result;
+  if (!ParseInt32(Message() << "The value of environment variable " << var,
+                  str_val, &result)) {
+    exit(EXIT_FAILURE);
+  }
+  return result;
+}
+
+// Given the total number of shards, the shard index, and the test id,
+// returns true iff the test should be run on this shard. The test id is
+// some arbitrary but unique non-negative integer assigned to each test
+// method. Assumes that 0 <= shard_index < total_shards.
+bool ShouldRunTestOnShard(int total_shards, int shard_index, int test_id) {
+  return (test_id % total_shards) == shard_index;
+}
+
 // Compares the name of each test with the user-specified filter to
 // decide whether the test should be run, then records the result in
 // each TestCase and TestInfo object.
+// If shard_tests == true, further filters tests based on sharding
+// variables in the environment - see
+// http://code.google.com/p/googletest/wiki/GoogleTestAdvancedGuide.
 // Returns the number of tests that should run.
-int UnitTestImpl::FilterTests() {
+int UnitTestImpl::FilterTests(ReactionToSharding shard_tests) {
+  const Int32 total_shards = shard_tests == HONOR_SHARDING_PROTOCOL ?
+    Int32FromEnvOrDie(kTestTotalShards, -1) : -1;
+  const Int32 shard_index = shard_tests == HONOR_SHARDING_PROTOCOL ?
+    Int32FromEnvOrDie(kTestShardIndex, -1) : -1;
+
+  // num_runnable_tests are the number of tests that will
+  // run across all shards (i.e., match filter and are not disabled).
+  // num_selected_tests are the number of tests to be run on
+  // this shard.
   int num_runnable_tests = 0;
+  int num_selected_tests = 0;
   for (const internal::ListNode<TestCase *> *test_case_node =
        test_cases_.Head();
        test_case_node != NULL;
@@ -3615,18 +3754,24 @@ int UnitTestImpl::FilterTests() {
                                                  kDisableTestFilter);
       test_info->impl()->set_is_disabled(is_disabled);
 
-      const bool should_run =
+      const bool is_runnable =
           (GTEST_FLAG(also_run_disabled_tests) || !is_disabled) &&
           internal::UnitTestOptions::FilterMatchesTest(test_case_name,
                                                        test_name);
-      test_info->impl()->set_should_run(should_run);
-      test_case->set_should_run(test_case->should_run() || should_run);
-      if (should_run) {
-        num_runnable_tests++;
-      }
+
+      const bool is_selected = is_runnable &&
+          (shard_tests == IGNORE_SHARDING_PROTOCOL ||
+           ShouldRunTestOnShard(total_shards, shard_index,
+                                num_runnable_tests));
+
+      num_runnable_tests += is_runnable;
+      num_selected_tests += is_selected;
+
+      test_info->impl()->set_should_run(is_selected);
+      test_case->set_should_run(test_case->should_run() || is_selected);
     }
   }
-  return num_runnable_tests;
+  return num_selected_tests;
 }
 
 // Lists all tests by name.
diff --git a/test/gtest_filter_unittest.py b/test/gtest_filter_unittest.py
index 35307a2..c3a016c 100755
--- a/test/gtest_filter_unittest.py
+++ b/test/gtest_filter_unittest.py
@@ -36,6 +36,9 @@ the GTEST_FILTER environment variable or the --gtest_filter flag.
 This script tests such functionality by invoking
 gtest_filter_unittest_ (a program written with Google Test) with different
 environments and command line flags.
+
+Note that test sharding may also influence which tests are filtered. Therefore,
+we test that here also.
 """
 
 __author__ = 'wan@google.com (Zhanyong Wan)'
@@ -43,6 +46,7 @@ __author__ = 'wan@google.com (Zhanyong Wan)'
 import os
 import re
 import sets
+import tempfile
 import unittest
 import gtest_test_utils
 
@@ -51,6 +55,11 @@ import gtest_test_utils
 # The environment variable for specifying the test filters.
 FILTER_ENV_VAR = 'GTEST_FILTER'
 
+# The environment variables for test sharding.
+TOTAL_SHARDS_ENV_VAR = 'GTEST_TOTAL_SHARDS'
+SHARD_INDEX_ENV_VAR = 'GTEST_SHARD_INDEX'
+SHARD_STATUS_FILE_ENV_VAR = 'GTEST_SHARD_STATUS_FILE'
+
 # The command line flag for specifying the test filters.
 FILTER_FLAG = 'gtest_filter'
 
@@ -103,6 +112,9 @@ ACTIVE_TESTS = [
     'BazTest.TestOne',
     'BazTest.TestA',
     'BazTest.TestB',
+
+    'HasDeathTest.Test1',
+    'HasDeathTest.Test2',
     ] + PARAM_TESTS
 
 param_tests_present = None
@@ -121,7 +133,7 @@ def SetEnvVar(env_var, value):
 
 def Run(command):
   """Runs a Google Test program and returns a list of full names of the
-  tests that were run.
+  tests that were run along with the test exit code.
   """
 
   stdout_file = os.popen(command, 'r')
@@ -137,9 +149,32 @@ def Run(command):
       if match is not None:
         test = match.group(1)
         tests_run += [test_case + '.' + test]
-  stdout_file.close()
-  return tests_run
+  exit_code = stdout_file.close()
+  return (tests_run, exit_code)
+
+
+def InvokeWithModifiedEnv(extra_env, function, *args, **kwargs):
+  """Runs the given function and arguments in a modified environment."""
+  try:
+    original_env = os.environ.copy()
+    os.environ.update(extra_env)
+    return function(*args, **kwargs)
+  finally:
+    for key in extra_env.iterkeys():
+      if key in original_env:
+        os.environ[key] = original_env[key]
+      else:
+        del os.environ[key]
+
+
+def RunWithSharding(total_shards, shard_index, command):
+  """Runs the Google Test program shard and returns a list of full names of the
+  tests that were run along with the exit code.
+  """
 
+  extra_env = {SHARD_INDEX_ENV_VAR: str(shard_index),
+               TOTAL_SHARDS_ENV_VAR: str(total_shards)}
+  return InvokeWithModifiedEnv(extra_env, Run, command)
 
 # The unit test.
 
@@ -160,6 +195,15 @@ class GTestFilterUnitTest(unittest.TestCase):
     for elem in rhs:
       self.assert_(elem in lhs, '%s in %s' % (elem, lhs))
 
+  def AssertPartitionIsValid(self, set_var, list_of_sets):
+    """Asserts that list_of_sets is a valid partition of set_var."""
+
+    full_partition = []
+    for slice_var in list_of_sets:
+      full_partition.extend(slice_var)
+    self.assertEqual(len(set_var), len(full_partition))
+    self.assertEqual(sorted(set_var), sorted(full_partition))
+
   def RunAndVerify(self, gtest_filter, tests_to_run):
     """Runs gtest_flag_unittest_ with the given filter, and verifies
     that the right set of tests were run.
@@ -173,7 +217,7 @@ class GTestFilterUnitTest(unittest.TestCase):
     # First, tests using GTEST_FILTER.
 
     SetEnvVar(FILTER_ENV_VAR, gtest_filter)
-    tests_run = Run(COMMAND)
+    tests_run = Run(COMMAND)[0]
     SetEnvVar(FILTER_ENV_VAR, None)
 
     self.AssertSetEqual(tests_run, tests_to_run)
@@ -185,9 +229,27 @@ class GTestFilterUnitTest(unittest.TestCase):
     else:
       command = '%s --%s=%s' % (COMMAND, FILTER_FLAG, gtest_filter)
 
-    tests_run = Run(command)
+    tests_run = Run(command)[0]
     self.AssertSetEqual(tests_run, tests_to_run)
 
+  def RunAndVerifyWithSharding(self, gtest_filter, total_shards, tests_to_run,
+                               command=COMMAND, check_exit_0=False):
+    """Runs all shards of gtest_flag_unittest_ with the given filter, and
+    verifies that the right set of tests were run. The union of tests run
+    on each shard should be identical to tests_to_run, without duplicates.
+    If check_exit_0, make sure that all shards returned 0.
+    """
+    SetEnvVar(FILTER_ENV_VAR, gtest_filter)
+    partition = []
+    for i in range(0, total_shards):
+      (tests_run, exit_code) = RunWithSharding(total_shards, i, command)
+      if check_exit_0:
+        self.assert_(exit_code is None)
+      partition.append(tests_run)
+
+    self.AssertPartitionIsValid(tests_to_run, partition)
+    SetEnvVar(FILTER_ENV_VAR, None)
+
   def RunAndVerifyAllowingDisabled(self, gtest_filter, tests_to_run):
     """Runs gtest_flag_unittest_ with the given filter, and enables
     disabled tests. Verifies that the right set of tests were run.
@@ -197,7 +259,7 @@ class GTestFilterUnitTest(unittest.TestCase):
     if gtest_filter is not None:
       command = '%s --%s=%s' % (command, FILTER_FLAG, gtest_filter)
 
-    tests_run = Run(command)
+    tests_run = Run(command)[0]
     self.AssertSetEqual(tests_run, tests_to_run)
 
   def setUp(self):
@@ -214,10 +276,22 @@ class GTestFilterUnitTest(unittest.TestCase):
 
     self.RunAndVerify(None, ACTIVE_TESTS)
 
+  def testDefaultBehaviorWithShards(self):
+    """Tests the behavior of not specifying the filter, with sharding
+    enabled.
+    """
+    self.RunAndVerifyWithSharding(None, 1, ACTIVE_TESTS)
+    self.RunAndVerifyWithSharding(None, 2, ACTIVE_TESTS)
+    self.RunAndVerifyWithSharding(None, len(ACTIVE_TESTS) - 1, ACTIVE_TESTS)
+    self.RunAndVerifyWithSharding(None, len(ACTIVE_TESTS), ACTIVE_TESTS)
+    self.RunAndVerifyWithSharding(None, len(ACTIVE_TESTS) + 1, ACTIVE_TESTS)
+
   def testEmptyFilter(self):
     """Tests an empty filter."""
 
     self.RunAndVerify('', [])
+    self.RunAndVerifyWithSharding('', 1, [])
+    self.RunAndVerifyWithSharding('', 2, [])
 
   def testBadFilter(self):
     """Tests a filter that matches nothing."""
@@ -230,12 +304,14 @@ class GTestFilterUnitTest(unittest.TestCase):
 
     self.RunAndVerify('FooTest.Xyz', ['FooTest.Xyz'])
     self.RunAndVerifyAllowingDisabled('FooTest.Xyz', ['FooTest.Xyz'])
+    self.RunAndVerifyWithSharding('FooTest.Xyz', 5, ['FooTest.Xyz'])
 
   def testUniversalFilters(self):
     """Tests filters that match everything."""
 
     self.RunAndVerify('*', ACTIVE_TESTS)
     self.RunAndVerify('*.*', ACTIVE_TESTS)
+    self.RunAndVerifyWithSharding('*.*', len(ACTIVE_TESTS) - 3, ACTIVE_TESTS)
     self.RunAndVerifyAllowingDisabled('*', ACTIVE_TESTS + DISABLED_TESTS)
     self.RunAndVerifyAllowingDisabled('*.*', ACTIVE_TESTS + DISABLED_TESTS)
 
@@ -289,7 +365,10 @@ class GTestFilterUnitTest(unittest.TestCase):
 
         'BazTest.TestOne',
         'BazTest.TestA',
-        'BazTest.TestB' ] + PARAM_TESTS)
+        'BazTest.TestB',
+
+        'HasDeathTest.Test1',
+        'HasDeathTest.Test2', ] + PARAM_TESTS)
 
   def testWildcardInTestName(self):
     """Tests using wildcard in the test name."""
@@ -350,7 +429,8 @@ class GTestFilterUnitTest(unittest.TestCase):
         ])
 
   def testNegativeFilters(self):
-    self.RunAndVerify('*-FooTest.Abc', [
+    self.RunAndVerify('*-HasDeathTest.Test1', [
+        'FooTest.Abc',
         'FooTest.Xyz',
 
         'BarTest.TestOne',
@@ -360,14 +440,20 @@ class GTestFilterUnitTest(unittest.TestCase):
         'BazTest.TestOne',
         'BazTest.TestA',
         'BazTest.TestB',
+
+        'HasDeathTest.Test2',
         ] + PARAM_TESTS)
 
-    self.RunAndVerify('*-FooTest.Abc:BazTest.*', [
+    self.RunAndVerify('*-FooTest.Abc:HasDeathTest.*', [
         'FooTest.Xyz',
 
         'BarTest.TestOne',
         'BarTest.TestTwo',
         'BarTest.TestThree',
+
+        'BazTest.TestOne',
+        'BazTest.TestA',
+        'BazTest.TestB',
         ] + PARAM_TESTS)
 
     self.RunAndVerify('BarTest.*-BarTest.TestOne', [
@@ -376,7 +462,7 @@ class GTestFilterUnitTest(unittest.TestCase):
         ])
 
     # Tests without leading '*'.
-    self.RunAndVerify('-FooTest.Abc:FooTest.Xyz', [
+    self.RunAndVerify('-FooTest.Abc:FooTest.Xyz:HasDeathTest.*', [
         'BarTest.TestOne',
         'BarTest.TestTwo',
         'BarTest.TestThree',
@@ -412,11 +498,65 @@ class GTestFilterUnitTest(unittest.TestCase):
 
     SetEnvVar(FILTER_ENV_VAR, 'Foo*')
     command = '%s --%s=%s' % (COMMAND, FILTER_FLAG, '*One')
-    tests_run = Run(command)
+    tests_run = Run(command)[0]
     SetEnvVar(FILTER_ENV_VAR, None)
 
     self.AssertSetEqual(tests_run, ['BarTest.TestOne', 'BazTest.TestOne'])
 
+  def testShardStatusFileIsCreated(self):
+    """Tests that the shard file is created if specified in the environment."""
+
+    test_tmpdir = tempfile.mkdtemp()
+    shard_status_file = os.path.join(test_tmpdir, 'shard_status_file')
+    self.assert_(not os.path.exists(shard_status_file))
+
+    extra_env = {SHARD_STATUS_FILE_ENV_VAR: shard_status_file}
+    stdout_file = InvokeWithModifiedEnv(extra_env, os.popen, COMMAND, 'r')
+    try:
+      stdout_file.readlines()
+    finally:
+      stdout_file.close()
+      self.assert_(os.path.exists(shard_status_file))
+      os.remove(shard_status_file)
+      os.removedirs(test_tmpdir)
+
+  def testShardStatusFileIsCreatedWithListTests(self):
+    """Tests that the shard file is created with --gtest_list_tests."""
+
+    test_tmpdir = tempfile.mkdtemp()
+    shard_status_file = os.path.join(test_tmpdir, 'shard_status_file2')
+    self.assert_(not os.path.exists(shard_status_file))
+
+    extra_env = {SHARD_STATUS_FILE_ENV_VAR: shard_status_file}
+    stdout_file = InvokeWithModifiedEnv(extra_env, os.popen,
+                                        '%s --gtest_list_tests' % COMMAND, 'r')
+    try:
+      stdout_file.readlines()
+    finally:
+      stdout_file.close()
+      self.assert_(os.path.exists(shard_status_file))
+      os.remove(shard_status_file)
+      os.removedirs(test_tmpdir)
+
+  def testShardingWorksWithDeathTests(self):
+    """Tests integration with death tests and sharding."""
+    gtest_filter = 'HasDeathTest.*:SeqP/*'
+    expected_tests = [
+        'HasDeathTest.Test1',
+        'HasDeathTest.Test2',
+
+        'SeqP/ParamTest.TestX/0',
+        'SeqP/ParamTest.TestX/1',
+        'SeqP/ParamTest.TestY/0',
+        'SeqP/ParamTest.TestY/1',
+        ]
+
+    for command in (COMMAND + ' --gtest_death_test_style=threadsafe',
+                    COMMAND + ' --gtest_death_test_style=fast'):
+      self.RunAndVerifyWithSharding(gtest_filter, 3, expected_tests,
+                                    check_exit_0=True, command=command)
+      self.RunAndVerifyWithSharding(gtest_filter, 5, expected_tests,
+                                    check_exit_0=True, command=command)
 
 if __name__ == '__main__':
   gtest_test_utils.Main()
diff --git a/test/gtest_filter_unittest_.cc b/test/gtest_filter_unittest_.cc
index 9961079..22638e0 100644
--- a/test/gtest_filter_unittest_.cc
+++ b/test/gtest_filter_unittest_.cc
@@ -91,6 +91,25 @@ TEST(BazTest, DISABLED_TestC) {
   FAIL() << "Expected failure.";
 }
 
+// Test case HasDeathTest
+
+TEST(HasDeathTest, Test1) {
+#ifdef GTEST_HAS_DEATH_TEST
+  EXPECT_DEATH({exit(1);},
+    ".*");
+#endif  // GTEST_HAS_DEATH_TEST
+}
+
+// We need at least two death tests to make sure that the all death tests
+// aren't on the first shard.
+TEST(HasDeathTest, Test2) {
+#ifdef GTEST_HAS_DEATH_TEST
+  EXPECT_DEATH({exit(1);},
+    ".*");
+#endif  // GTEST_HAS_DEATH_TEST
+}
+
+
 // Test case FoobarTest
 
 TEST(DISABLED_FoobarTest, Test1) {
diff --git a/test/gtest_output_test.py b/test/gtest_output_test.py
index 9aaade2..f35e002 100755
--- a/test/gtest_output_test.py
+++ b/test/gtest_output_test.py
@@ -64,13 +64,17 @@ PROGRAM_PATH = os.path.join(gtest_test_utils.GetBuildDir(), PROGRAM)
 
 # At least one command we exercise must not have the
 # --gtest_internal_skip_environment_and_ad_hoc_tests flag.
-COMMAND_WITH_COLOR = PROGRAM_PATH + ' --gtest_color=yes'
-COMMAND_WITH_TIME = (PROGRAM_PATH + ' --gtest_print_time '
+COMMAND_WITH_COLOR = ({}, PROGRAM_PATH + ' --gtest_color=yes')
+COMMAND_WITH_TIME = ({}, PROGRAM_PATH + ' --gtest_print_time '
                      '--gtest_internal_skip_environment_and_ad_hoc_tests '
                      '--gtest_filter="FatalFailureTest.*:LoggingTest.*"')
-COMMAND_WITH_DISABLED = (PROGRAM_PATH + ' --gtest_also_run_disabled_tests '
+COMMAND_WITH_DISABLED = ({}, PROGRAM_PATH + ' --gtest_also_run_disabled_tests '
                          '--gtest_internal_skip_environment_and_ad_hoc_tests '
                          '--gtest_filter="*DISABLED_*"')
+COMMAND_WITH_SHARDING = ({'GTEST_SHARD_INDEX': '1', 'GTEST_TOTAL_SHARDS': '2'},
+                         PROGRAM_PATH +
+                         ' --gtest_internal_skip_environment_and_ad_hoc_tests '
+                         ' --gtest_filter="PassingTest.*"')
 
 GOLDEN_PATH = os.path.join(gtest_test_utils.GetSourceDir(),
                            GOLDEN_NAME)
@@ -136,19 +140,26 @@ def NormalizeOutput(output):
   return output
 
 
-def IterShellCommandOutput(cmd, stdin_string=None):
+def IterShellCommandOutput(env_cmd, stdin_string=None):
   """Runs a command in a sub-process, and iterates the lines in its STDOUT.
 
   Args:
 
-    cmd:           The shell command.
-    stdin_string:  The string to be fed to the STDIN of the sub-process;
-                   If None, the sub-process will inherit the STDIN
-                   from the parent process.
+    env_cmd:           The shell command. A 2-tuple where element 0 is a dict
+                       of extra environment variables to set, and element 1
+                       is a string with the command and any flags.
+    stdin_string:      The string to be fed to the STDIN of the sub-process;
+                       If None, the sub-process will inherit the STDIN
+                       from the parent process.
   """
 
   # Spawns cmd in a sub-process, and gets its standard I/O file objects.
-  stdin_file, stdout_file = os.popen2(cmd, 'b')
+  # Set and save the environment properly.
+  old_env_vars = dict(os.environ)
+  os.environ.update(env_cmd[0])
+  stdin_file, stdout_file = os.popen2(env_cmd[1], 'b')
+  os.environ.clear()
+  os.environ.update(old_env_vars)
 
   # If the caller didn't specify a string for STDIN, gets it from the
   # parent process.
@@ -168,39 +179,50 @@ def IterShellCommandOutput(cmd, stdin_string=None):
     yield line
 
 
-def GetShellCommandOutput(cmd, stdin_string=None):
+def GetShellCommandOutput(env_cmd, stdin_string=None):
   """Runs a command in a sub-process, and returns its STDOUT in a string.
 
   Args:
 
-    cmd:           The shell command.
-    stdin_string:  The string to be fed to the STDIN of the sub-process;
-                   If None, the sub-process will inherit the STDIN
-                   from the parent process.
+    env_cmd:           The shell command. A 2-tuple where element 0 is a dict
+                       of extra environment variables to set, and element 1
+                       is a string with the command and any flags.
+    stdin_string:      The string to be fed to the STDIN of the sub-process;
+                       If None, the sub-process will inherit the STDIN
+                       from the parent process.
   """
 
-  lines = list(IterShellCommandOutput(cmd, stdin_string))
+  lines = list(IterShellCommandOutput(env_cmd, stdin_string))
   return string.join(lines, '')
 
 
-def GetCommandOutput(cmd):
+def GetCommandOutput(env_cmd):
   """Runs a command and returns its output with all file location
   info stripped off.
 
   Args:
-    cmd:  the shell command.
+    env_cmd:  The shell command. A 2-tuple where element 0 is a dict of extra
+              environment variables to set, and element 1 is a string with
+              the command and any flags.
   """
 
   # Disables exception pop-ups on Windows.
   os.environ['GTEST_CATCH_EXCEPTIONS'] = '1'
-  return NormalizeOutput(GetShellCommandOutput(cmd, ''))
+  return NormalizeOutput(GetShellCommandOutput(env_cmd, ''))
+
+
+def GetOutputOfAllCommands():
+  """Returns concatenated output from several representative commands."""
+
+  return (GetCommandOutput(COMMAND_WITH_COLOR) +
+          GetCommandOutput(COMMAND_WITH_TIME) +
+          GetCommandOutput(COMMAND_WITH_DISABLED) +
+          GetCommandOutput(COMMAND_WITH_SHARDING))
 
 
 class GTestOutputTest(unittest.TestCase):
   def testOutput(self):
-    output = (GetCommandOutput(COMMAND_WITH_COLOR) +
-              GetCommandOutput(COMMAND_WITH_TIME) +
-              GetCommandOutput(COMMAND_WITH_DISABLED))
+    output = GetOutputOfAllCommands()
     golden_file = open(GOLDEN_PATH, 'rb')
     golden = golden_file.read()
     golden_file.close()
@@ -214,9 +236,7 @@ class GTestOutputTest(unittest.TestCase):
 
 if __name__ == '__main__':
   if sys.argv[1:] == [GENGOLDEN_FLAG]:
-    output = (GetCommandOutput(COMMAND_WITH_COLOR) +
-              GetCommandOutput(COMMAND_WITH_TIME) +
-              GetCommandOutput(COMMAND_WITH_DISABLED))
+    output = GetOutputOfAllCommands()
     golden_file = open(GOLDEN_PATH, 'wb')
     golden_file.write(output)
     golden_file.close()
diff --git a/test/gtest_output_test_.cc b/test/gtest_output_test_.cc
index 5c76609..f5748d1 100644
--- a/test/gtest_output_test_.cc
+++ b/test/gtest_output_test_.cc
@@ -85,6 +85,12 @@ void TryTestSubroutine() {
   FAIL() << "This should never be reached.";
 }
 
+TEST(PassingTest, PassingTest1) {
+}
+
+TEST(PassingTest, PassingTest2) {
+}
+
 // Tests catching a fatal failure in a subroutine.
 TEST(FatalFailureTest, FatalFailureInSubroutine) {
   printf("(expecting a failure that x should be 1)\n");
diff --git a/test/gtest_output_test_golden_lin.txt b/test/gtest_output_test_golden_lin.txt
index 74ed737..46a90fb 100644
--- a/test/gtest_output_test_golden_lin.txt
+++ b/test/gtest_output_test_golden_lin.txt
@@ -7,7 +7,7 @@ Expected: true
 gtest_output_test_.cc:#: Failure
 Value of: 3
 Expected: 2
-[==========] Running 54 tests from 22 test cases.
+[==========] Running 56 tests from 23 test cases.
 [----------] Global test environment set-up.
 FooEnvironment::SetUp() called.
 BarEnvironment::SetUp() called.
@@ -26,6 +26,11 @@ BarEnvironment::SetUp() called.
 [----------] 1 test from My/ATypeParamDeathTest/1, where TypeParam = double
 [ RUN      ] My/ATypeParamDeathTest/1.ShouldRunFirst
 [       OK ] My/ATypeParamDeathTest/1.ShouldRunFirst
+[----------] 2 tests from PassingTest
+[ RUN      ] PassingTest.PassingTest1
+[       OK ] PassingTest.PassingTest1
+[ RUN      ] PassingTest.PassingTest2
+[       OK ] PassingTest.PassingTest2
 [----------] 3 tests from FatalFailureTest
 [ RUN      ] FatalFailureTest.FatalFailureInSubroutine
 (expecting a failure that x should be 1)
@@ -508,8 +513,8 @@ FooEnvironment::TearDown() called.
 gtest_output_test_.cc:#: Failure
 Failed
 Expected fatal failure.
-[==========] 54 tests from 22 test cases ran.
-[  PASSED  ] 19 tests.
+[==========] 56 tests from 23 test cases ran.
+[  PASSED  ] 21 tests.
 [  FAILED  ] 35 tests, listed below:
 [  FAILED  ] FatalFailureTest.FatalFailureInSubroutine
 [  FAILED  ] FatalFailureTest.FatalFailureInNestedSubroutine
@@ -612,3 +617,16 @@ Note: Google Test filter = *DISABLED_*
 [----------] Global test environment tear-down
 [==========] 1 test from 1 test case ran.
 [  PASSED  ] 1 test.
+Note: Google Test filter = PassingTest.*
+Note: This is test shard 1 of 2.
+[==========] Running 1 test from 1 test case.
+[----------] Global test environment set-up.
+[----------] 1 test from PassingTest
+[ RUN      ] PassingTest.PassingTest2
+[       OK ] PassingTest.PassingTest2
+[----------] Global test environment tear-down
+[==========] 1 test from 1 test case ran.
+[  PASSED  ] 1 test.
+
+  YOU HAVE 1 DISABLED TEST
+
diff --git a/test/gtest_output_test_golden_win.txt b/test/gtest_output_test_golden_win.txt
index 17be5c0..77903ba 100644
--- a/test/gtest_output_test_golden_win.txt
+++ b/test/gtest_output_test_golden_win.txt
@@ -5,10 +5,15 @@ gtest_output_test_.cc:#: error: Value of: false
 Expected: true
 gtest_output_test_.cc:#: error: Value of: 3
 Expected: 2
-[==========] Running 50 tests from 20 test cases.
+[==========] Running 52 tests from 21 test cases.
 [----------] Global test environment set-up.
 FooEnvironment::SetUp() called.
 BarEnvironment::SetUp() called.
+[----------] 2 tests from PassingTest
+[ RUN      ] PassingTest.PassingTest1
+[       OK ] PassingTest.PassingTest1
+[ RUN      ] PassingTest.PassingTest2
+[       OK ] PassingTest.PassingTest2
 [----------] 3 tests from FatalFailureTest
 [ RUN      ] FatalFailureTest.FatalFailureInSubroutine
 (expecting a failure that x should be 1)
@@ -440,8 +445,8 @@ Expected non-fatal failure.
 FooEnvironment::TearDown() called.
 gtest_output_test_.cc:#: error: Failed
 Expected fatal failure.
-[==========] 50 tests from 20 test cases ran.
-[  PASSED  ] 14 tests.
+[==========] 52 tests from 21 test cases ran.
+[  PASSED  ] 16 tests.
 [  FAILED  ] 36 tests, listed below:
 [  FAILED  ] FatalFailureTest.FatalFailureInSubroutine
 [  FAILED  ] FatalFailureTest.FatalFailureInNestedSubroutine
@@ -540,3 +545,16 @@ Note: Google Test filter = *DISABLED_*
 [----------] Global test environment tear-down
 [==========] 1 test from 1 test case ran.
 [  PASSED  ] 1 test.
+Note: Google Test filter = PassingTest.*
+Note: This is test shard 1 of 2.
+[==========] Running 1 test from 1 test case.
+[----------] Global test environment set-up.
+[----------] 1 test from PassingTest
+[ RUN      ] PassingTest.PassingTest2
+[       OK ] PassingTest.PassingTest2
+[----------] Global test environment tear-down
+[==========] 1 test from 1 test case ran.
+[  PASSED  ] 1 test.
+
+  YOU HAVE 1 DISABLED TEST
+
diff --git a/test/gtest_unittest.cc b/test/gtest_unittest.cc
index 4bac8a6..335b9e0 100644
--- a/test/gtest_unittest.cc
+++ b/test/gtest_unittest.cc
@@ -138,7 +138,10 @@ using testing::internal::GetTestTypeId;
 using testing::internal::GetTypeId;
 using testing::internal::GTestFlagSaver;
 using testing::internal::Int32;
+using testing::internal::Int32FromEnvOrDie;
 using testing::internal::List;
+using testing::internal::ShouldRunTestOnShard;
+using testing::internal::ShouldShard;
 using testing::internal::ShouldUseColor;
 using testing::internal::StreamableToString;
 using testing::internal::String;
@@ -1375,6 +1378,161 @@ TEST(ParseInt32FlagTest, ParsesAndReturnsValidValue) {
   EXPECT_EQ(-789, value);
 }
 
+// Tests that Int32FromEnvOrDie() parses the value of the var or
+// returns the correct default.
+TEST(Int32FromEnvOrDieTest, ParsesAndReturnsValidValue) {
+  EXPECT_EQ(333, Int32FromEnvOrDie(GTEST_FLAG_PREFIX_UPPER "UnsetVar", 333));
+  SetEnv(GTEST_FLAG_PREFIX_UPPER "UnsetVar", "123");
+  EXPECT_EQ(123, Int32FromEnvOrDie(GTEST_FLAG_PREFIX_UPPER "UnsetVar", 333));
+  SetEnv(GTEST_FLAG_PREFIX_UPPER "UnsetVar", "-123");
+  EXPECT_EQ(-123, Int32FromEnvOrDie(GTEST_FLAG_PREFIX_UPPER "UnsetVar", 333));
+}
+
+#ifdef GTEST_HAS_DEATH_TEST
+
+// Tests that Int32FromEnvOrDie() aborts with an error message
+// if the variable is not an Int32.
+TEST(Int32FromEnvOrDieDeathTest, AbortsOnFailure) {
+  SetEnv(GTEST_FLAG_PREFIX_UPPER "VAR", "xxx");
+  EXPECT_DEATH({Int32FromEnvOrDie(GTEST_FLAG_PREFIX_UPPER "VAR", 123);},
+               ".*");
+}
+
+// Tests that Int32FromEnvOrDie() aborts with an error message
+// if the variable cannot be represnted by an Int32.
+TEST(Int32FromEnvOrDieDeathTest, AbortsOnInt32Overflow) {
+  SetEnv(GTEST_FLAG_PREFIX_UPPER "VAR", "1234567891234567891234");
+  EXPECT_DEATH({Int32FromEnvOrDie(GTEST_FLAG_PREFIX_UPPER "VAR", 123);},
+               ".*");
+}
+
+#endif  // GTEST_HAS_DEATH_TEST
+
+
+// Tests that ShouldRunTestOnShard() selects all tests
+// where there is 1 shard.
+TEST(ShouldRunTestOnShardTest, IsPartitionWhenThereIsOneShard) {
+  EXPECT_TRUE(ShouldRunTestOnShard(1, 0, 0));
+  EXPECT_TRUE(ShouldRunTestOnShard(1, 0, 1));
+  EXPECT_TRUE(ShouldRunTestOnShard(1, 0, 2));
+  EXPECT_TRUE(ShouldRunTestOnShard(1, 0, 3));
+  EXPECT_TRUE(ShouldRunTestOnShard(1, 0, 4));
+}
+
+class ShouldShardTest : public testing::Test {
+ protected:
+  virtual void SetUp() {
+    index_var_ = GTEST_FLAG_PREFIX_UPPER "INDEX";
+    total_var_ = GTEST_FLAG_PREFIX_UPPER "TOTAL";
+  }
+
+  virtual void TearDown() {
+    SetEnv(index_var_, "");
+    SetEnv(total_var_, "");
+  }
+
+  const char* index_var_;
+  const char* total_var_;
+};
+
+// Tests that sharding is disabled if neither of the environment variables
+// are set.
+TEST_F(ShouldShardTest, ReturnsFalseWhenNeitherEnvVarIsSet) {
+  SetEnv(index_var_, "");
+  SetEnv(total_var_, "");
+
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, false));
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, true));
+}
+
+// Tests that sharding is not enabled if total_shards  == 1.
+TEST_F(ShouldShardTest, ReturnsFalseWhenTotalShardIsOne) {
+  SetEnv(index_var_, "0");
+  SetEnv(total_var_, "1");
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, false));
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, true));
+}
+
+// Tests that sharding is enabled if total_shards > 1 and
+// we are not in a death test subprocess.
+TEST_F(ShouldShardTest, WorksWhenShardEnvVarsAreValid) {
+  SetEnv(index_var_, "4");
+  SetEnv(total_var_, "22");
+  EXPECT_TRUE(ShouldShard(total_var_, index_var_, false));
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, true));
+
+  SetEnv(index_var_, "8");
+  SetEnv(total_var_, "9");
+  EXPECT_TRUE(ShouldShard(total_var_, index_var_, false));
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, true));
+
+  SetEnv(index_var_, "0");
+  SetEnv(total_var_, "9");
+  EXPECT_TRUE(ShouldShard(total_var_, index_var_, false));
+  EXPECT_FALSE(ShouldShard(total_var_, index_var_, true));
+}
+
+#ifdef GTEST_HAS_DEATH_TEST
+
+// Tests that we exit in error if the sharding values are not valid.
+TEST_F(ShouldShardTest, AbortsWhenShardingEnvVarsAreInvalid) {
+  SetEnv(index_var_, "4");
+  SetEnv(total_var_, "4");
+  EXPECT_DEATH({ShouldShard(total_var_, index_var_, false);},
+               ".*");
+
+  SetEnv(index_var_, "4");
+  SetEnv(total_var_, "-2");
+  EXPECT_DEATH({ShouldShard(total_var_, index_var_, false);},
+               ".*");
+
+  SetEnv(index_var_, "5");
+  SetEnv(total_var_, "");
+  EXPECT_DEATH({ShouldShard(total_var_, index_var_, false);},
+               ".*");
+
+  SetEnv(index_var_, "");
+  SetEnv(total_var_, "5");
+  EXPECT_DEATH({ShouldShard(total_var_, index_var_, false);},
+               ".*");
+}
+
+#endif  // GTEST_HAS_DEATH_TEST
+
+// Tests that ShouldRunTestOnShard is a partition when 5
+// shards are used.
+TEST(ShouldRunTestOnShardTest, IsPartitionWhenThereAreFiveShards) {
+  // Choose an arbitrary number of tests and shards.
+  const int num_tests = 17;
+  const int num_shards = 5;
+
+  // Check partitioning: each test should be on exactly 1 shard.
+  for (int test_id = 0; test_id < num_tests; test_id++) {
+    int prev_selected_shard_index = -1;
+    for (int shard_index = 0; shard_index < num_shards; shard_index++) {
+      if (ShouldRunTestOnShard(num_shards, shard_index, test_id)) {
+        if (prev_selected_shard_index < 0) {
+          prev_selected_shard_index = shard_index;
+        } else {
+          ADD_FAILURE() << "Shard " << prev_selected_shard_index << " and "
+            << shard_index << " are both selected to run test " << test_id;
+        }
+      }
+    }
+  }
+
+  // Check balance: This is not required by the sharding protocol, but is a
+  // desirable property for performance.
+  for (int shard_index = 0; shard_index < num_shards; shard_index++) {
+    int num_tests_on_shard = 0;
+    for (int test_id = 0; test_id < num_tests; test_id++) {
+      num_tests_on_shard +=
+        ShouldRunTestOnShard(num_shards, shard_index, test_id);
+    }
+    EXPECT_GE(num_tests_on_shard, num_tests / num_shards);
+  }
+}
+
 // For the same reason we are not explicitly testing everything in the
 // Test class, there are no separate tests for the following classes
 // (except for some trivial cases):