[mojo] Ports EDK

mojo/edk/system/multiprocess_message_pipe_unittest.cc

Index: mojo/edk/system/multiprocess_message_pipe_unittest.cc
diff --git a/mojo/edk/system/multiprocess_message_pipe_unittest.cc b/mojo/edk/system/multiprocess_message_pipe_unittest.cc
index 40622321e87503defa9af6b03f19c227647efa92..00c2ab564d4c3df196c0c93d337e1f99a6430b2e 100644
--- a/mojo/edk/system/multiprocess_message_pipe_unittest.cc
+++ b/mojo/edk/system/multiprocess_message_pipe_unittest.cc
@@ -6,29 +6,27 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>
+
 #include <string>
 #include <utility>
 #include <vector>
 
-#include "base/bind.h"
+#include "base/containers/hash_tables.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/files/scoped_temp_dir.h"
-#include "base/location.h"
 #include "base/logging.h"
+#include "base/strings/string_split.h"
 #include "build/build_config.h"
-#include "mojo/edk/embedder/embedder.h"
-#include "mojo/edk/embedder/platform_channel_pair.h"
-#include "mojo/edk/embedder/platform_shared_buffer.h"
 #include "mojo/edk/embedder/scoped_platform_handle.h"
-#include "mojo/edk/system/dispatcher.h"
-#include "mojo/edk/system/message_pipe_test_utils.h"
-#include "mojo/edk/system/platform_handle_dispatcher.h"
-#include "mojo/edk/system/raw_channel.h"
-#include "mojo/edk/system/shared_buffer_dispatcher.h"
+#include "mojo/edk/system/handle_signals_state.h"
 #include "mojo/edk/system/test_utils.h"
+#include "mojo/edk/test/mojo_test_base.h"
 #include "mojo/edk/test/test_utils.h"
+#include "mojo/public/c/system/buffer.h"
+#include "mojo/public/c/system/functions.h"
+#include "mojo/public/c/system/types.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 
@@ -36,27 +34,50 @@ namespace mojo {
 namespace edk {
 namespace {
 
-class MultiprocessMessagePipeTest
-    : public test::MultiprocessMessagePipeTestBase {};
+class MultiprocessMessagePipeTest : public test::MojoTestBase {
+ protected:
+  // Convenience class for tests which will control command-driven children.
+  // See the CommandDrivenClient definition below.
+  class CommandDrivenClientController {
+   public:
+    explicit CommandDrivenClientController(MojoHandle h) : h_(h) {}
+
+    void Send(const std::string& command) {
+      WriteMessage(h_, command);
+      EXPECT_EQ("ok", ReadMessage(h_));
+    }
+
+    void SendHandle(const std::string& name, MojoHandle p) {
+      WriteMessageWithHandles(h_, "take:" + name, &p, 1);
+      EXPECT_EQ("ok", ReadMessage(h_));
+    }
+
+    MojoHandle RetrieveHandle(const std::string& name) {
+      WriteMessage(h_, "return:" + name);
+      MojoHandle p;
+      EXPECT_EQ("ok", ReadMessageWithHandles(h_, &p, 1));
+      return p;
+    }
+
+    void Exit() { WriteMessage(h_, "exit"); }
+
+   private:
+    MojoHandle h_;
+  };
+};
 
 // For each message received, sends a reply message with the same contents
 // repeated twice, until the other end is closed or it receives "quitquitquit"
 // (which it doesn't reply to). It'll return the number of messages received,
 // not including any "quitquitquit" message, modulo 100.
-MOJO_MULTIPROCESS_TEST_CHILD_MAIN(EchoEcho) {
-  ScopedPlatformHandle client_platform_handle =
-      std::move(test::MultiprocessTestHelper::client_platform_handle);
-  CHECK(client_platform_handle.is_valid());
-  ScopedMessagePipeHandle mp =
-      CreateMessagePipe(std::move(client_platform_handle));
-
+DEFINE_TEST_CLIENT_WITH_PIPE(EchoEcho, MultiprocessMessagePipeTest, h) {
   const std::string quitquitquit("quitquitquit");
   int rv = 0;
   for (;; rv = (rv + 1) % 100) {
     // Wait for our end of the message pipe to be readable.
     HandleSignalsState hss;
     MojoResult result =
-        MojoWait(mp.get().value(), MOJO_HANDLE_SIGNAL_READABLE,
+        MojoWait(h, MOJO_HANDLE_SIGNAL_READABLE,
                  MOJO_DEADLINE_INDEFINITE, &hss);
     if (result != MOJO_RESULT_OK) {
       // It was closed, probably.
@@ -71,7 +92,7 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(EchoEcho) {
 
     std::string read_buffer(1000, '\0');
     uint32_t read_buffer_size = static_cast<uint32_t>(read_buffer.size());
-    CHECK_EQ(MojoReadMessage(mp.get().value(), &read_buffer[0],
+    CHECK_EQ(MojoReadMessage(h, &read_buffer[0],
                              &read_buffer_size, nullptr,
                              0, MOJO_READ_MESSAGE_FLAG_NONE),
              MOJO_RESULT_OK);
@@ -84,13 +105,13 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(EchoEcho) {
     }
 
     std::string write_buffer = read_buffer + read_buffer;
-    CHECK_EQ(MojoWriteMessage(mp.get().value(), write_buffer.data(),
+    CHECK_EQ(MojoWriteMessage(h, write_buffer.data(),
                               static_cast<uint32_t>(write_buffer.size()),
                               nullptr, 0u, MOJO_WRITE_MESSAGE_FLAG_NONE),
              MOJO_RESULT_OK);
   }
 
-   return rv;
+  return rv;
 }
 
 // Sends "hello" to child, and expects "hellohello" back.
@@ -101,41 +122,39 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(EchoEcho) {
 #define MAYBE_Basic Basic
 #endif  // defined(OS_ANDROID)
 TEST_F(MultiprocessMessagePipeTest, MAYBE_Basic) {
-  helper()->StartChild("EchoEcho");
-
-  ScopedMessagePipeHandle mp =
-      CreateMessagePipe(std::move(helper()->server_platform_handle));
-
-  std::string hello("hello");
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWriteMessage(mp.get().value(), hello.data(),
-                             static_cast<uint32_t>(hello.size()), nullptr, 0u,
-                             MOJO_WRITE_MESSAGE_FLAG_NONE));
+  RUN_CHILD_ON_PIPE(EchoEcho, h)
+    std::string hello("hello");
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(h, hello.data(),
+                               static_cast<uint32_t>(hello.size()), nullptr, 0u,
+                               MOJO_WRITE_MESSAGE_FLAG_NONE));
 
-  HandleSignalsState hss;
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWait(mp.get().value(), MOJO_HANDLE_SIGNAL_READABLE,
-               MOJO_DEADLINE_INDEFINITE, &hss));
-  // The child may or may not have closed its end of the message pipe and died
-  // (and we may or may not know it yet), so our end may or may not appear as
-  // writable.
-  EXPECT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE));
-  EXPECT_TRUE((hss.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE));
-
-  std::string read_buffer(1000, '\0');
-  uint32_t read_buffer_size = static_cast<uint32_t>(read_buffer.size());
-  CHECK_EQ(MojoReadMessage(mp.get().value(), &read_buffer[0],
-                           &read_buffer_size, nullptr, 0,
-                           MOJO_READ_MESSAGE_FLAG_NONE),
-           MOJO_RESULT_OK);
-  read_buffer.resize(read_buffer_size);
-  VLOG(2) << "Parent got: " << read_buffer;
-  ASSERT_EQ(hello + hello, read_buffer);
+    HandleSignalsState hss;
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWait(h, MOJO_HANDLE_SIGNAL_READABLE,
+                       MOJO_DEADLINE_INDEFINITE, &hss));
+    // The child may or may not have closed its end of the message pipe and died
+    // (and we may or may not know it yet), so our end may or may not appear as
+    // writable.
+    EXPECT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE));
+    EXPECT_TRUE((hss.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE));
 
-  MojoClose(mp.release().value());
+    std::string read_buffer(1000, '\0');
+    uint32_t read_buffer_size = static_cast<uint32_t>(read_buffer.size());
+    CHECK_EQ(MojoReadMessage(h, &read_buffer[0],
+                             &read_buffer_size, nullptr, 0,
+                             MOJO_READ_MESSAGE_FLAG_NONE),
+             MOJO_RESULT_OK);
+    read_buffer.resize(read_buffer_size);
+    VLOG(2) << "Parent got: " << read_buffer;
+    ASSERT_EQ(hello + hello, read_buffer);
 
-  // We sent one message.
-  ASSERT_EQ(1 % 100, helper()->WaitForChildShutdown());
+    std::string quitquitquit("quitquitquit");
+    CHECK_EQ(MojoWriteMessage(h, quitquitquit.data(),
+                              static_cast<uint32_t>(quitquitquit.size()),
+                              nullptr, 0u, MOJO_WRITE_MESSAGE_FLAG_NONE),
+             MOJO_RESULT_OK);
+  END_CHILD_AND_EXPECT_EXIT_CODE(1 % 100);
 }
 
 // Sends a bunch of messages to the child. Expects them "repeated" back. Waits
@@ -147,71 +166,60 @@ TEST_F(MultiprocessMessagePipeTest, MAYBE_Basic) {
 #define MAYBE_QueueMessages QueueMessages
 #endif  // defined(OS_ANDROID)
 TEST_F(MultiprocessMessagePipeTest, MAYBE_QueueMessages) {
-  helper()->StartChild("EchoEcho");
+  static const size_t kNumMessages = 1001;
+  RUN_CHILD_ON_PIPE(EchoEcho, h)
+    for (size_t i = 0; i < kNumMessages; i++) {
+      std::string write_buffer(i, 'A' + (i % 26));
+      ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(h, write_buffer.data(),
+                               static_cast<uint32_t>(write_buffer.size()),
+                               nullptr, 0u, MOJO_WRITE_MESSAGE_FLAG_NONE));
+    }
 
-  ScopedMessagePipeHandle mp =
-      CreateMessagePipe(std::move(helper()->server_platform_handle));
+    for (size_t i = 0; i < kNumMessages; i++) {
+      HandleSignalsState hss;
+      ASSERT_EQ(MOJO_RESULT_OK,
+                MojoWait(h, MOJO_HANDLE_SIGNAL_READABLE,
+                         MOJO_DEADLINE_INDEFINITE, &hss));
+      // The child may or may not have closed its end of the message pipe and
+      // died (and we may or may not know it yet), so our end may or may not
+      // appear as writable.
+      ASSERT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE));
+      ASSERT_TRUE((hss.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE));
+
+      std::string read_buffer(kNumMessages * 2, '\0');
+      uint32_t read_buffer_size = static_cast<uint32_t>(read_buffer.size());
+      ASSERT_EQ(MojoReadMessage(h, &read_buffer[0],
+                                &read_buffer_size, nullptr, 0,
+                                MOJO_READ_MESSAGE_FLAG_NONE),
+               MOJO_RESULT_OK);
+      read_buffer.resize(read_buffer_size);
+
+      ASSERT_EQ(std::string(i * 2, 'A' + (i % 26)), read_buffer);
+    }
 
-  static const size_t kNumMessages = 1001;
-  for (size_t i = 0; i < kNumMessages; i++) {
-    std::string write_buffer(i, 'A' + (i % 26));
+    const std::string quitquitquit("quitquitquit");
     ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWriteMessage(mp.get().value(), write_buffer.data(),
-                             static_cast<uint32_t>(write_buffer.size()),
-                             nullptr, 0u, MOJO_WRITE_MESSAGE_FLAG_NONE));
-  }
+              MojoWriteMessage(h, quitquitquit.data(),
+                               static_cast<uint32_t>(quitquitquit.size()),
+                               nullptr, 0u, MOJO_WRITE_MESSAGE_FLAG_NONE));
 
-  for (size_t i = 0; i < kNumMessages; i++) {
+    // Wait for it to become readable, which should fail (since we sent
+    // "quitquitquit").
     HandleSignalsState hss;
-    ASSERT_EQ(MOJO_RESULT_OK,
-              MojoWait(mp.get().value(), MOJO_HANDLE_SIGNAL_READABLE,
+    ASSERT_EQ(MOJO_RESULT_FAILED_PRECONDITION,
+              MojoWait(h, MOJO_HANDLE_SIGNAL_READABLE,
                        MOJO_DEADLINE_INDEFINITE, &hss));
-    // The child may or may not have closed its end of the message pipe and died
-    // (and we may or may not know it yet), so our end may or may not appear as
-    // writable.
-    ASSERT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE));
-    ASSERT_TRUE((hss.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE));
-
-    std::string read_buffer(kNumMessages * 2, '\0');
-    uint32_t read_buffer_size = static_cast<uint32_t>(read_buffer.size());
-    ASSERT_EQ(MojoReadMessage(mp.get().value(), &read_buffer[0],
-                             &read_buffer_size, nullptr, 0,
-                             MOJO_READ_MESSAGE_FLAG_NONE),
-             MOJO_RESULT_OK);
-    read_buffer.resize(read_buffer_size);
-
-    ASSERT_EQ(std::string(i * 2, 'A' + (i % 26)), read_buffer);
-  }
-
-  const std::string quitquitquit("quitquitquit");
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWriteMessage(mp.get().value(), quitquitquit.data(),
-                             static_cast<uint32_t>(quitquitquit.size()),
-                             nullptr, 0u, MOJO_WRITE_MESSAGE_FLAG_NONE));
-
-  // Wait for it to become readable, which should fail (since we sent
-  // "quitquitquit").
-  HandleSignalsState hss;
-  ASSERT_EQ(MOJO_RESULT_FAILED_PRECONDITION,
-            MojoWait(mp.get().value(), MOJO_HANDLE_SIGNAL_READABLE,
-                     MOJO_DEADLINE_INDEFINITE, &hss));
-  ASSERT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, hss.satisfied_signals);
-  ASSERT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, hss.satisfiable_signals);
-
-  ASSERT_EQ(static_cast<int>(kNumMessages % 100),
-            helper()->WaitForChildShutdown());
+    ASSERT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, hss.satisfied_signals);
+    ASSERT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, hss.satisfiable_signals);
+  END_CHILD_AND_EXPECT_EXIT_CODE(static_cast<int>(kNumMessages % 100));
 }
 
-MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckSharedBuffer) {
-  ScopedPlatformHandle client_platform_handle =
-      std::move(test::MultiprocessTestHelper::client_platform_handle);
-  CHECK(client_platform_handle.is_valid());
-  ScopedMessagePipeHandle mp =
-      CreateMessagePipe(std::move(client_platform_handle));
-
+DEFINE_TEST_CLIENT_WITH_PIPE(CheckSharedBuffer, MultiprocessMessagePipeTest,
+                             h) {
   // Wait for the first message from our parent.
   HandleSignalsState hss;
-  CHECK_EQ(MojoWait(mp.get().value(), MOJO_HANDLE_SIGNAL_READABLE,
+  CHECK_EQ(MojoWait(h, MOJO_HANDLE_SIGNAL_READABLE,
                MOJO_DEADLINE_INDEFINITE, &hss),
            MOJO_RESULT_OK);
   // In this test, the parent definitely doesn't close its end of the message
@@ -227,7 +235,7 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckSharedBuffer) {
   uint32_t num_bytes = static_cast<uint32_t>(read_buffer.size());
   MojoHandle handles[10];
   uint32_t num_handlers = MOJO_ARRAYSIZE(handles);  // Maximum number to receive
-  CHECK_EQ(MojoReadMessage(mp.get().value(), &read_buffer[0],
+  CHECK_EQ(MojoReadMessage(h, &read_buffer[0],
                            &num_bytes, &handles[0],
                            &num_handlers, MOJO_READ_MESSAGE_FLAG_NONE),
            MOJO_RESULT_OK);
@@ -250,15 +258,15 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckSharedBuffer) {
 
   // And send a message to signal that we've written stuff.
   const std::string go2("go 2");
-  CHECK_EQ(MojoWriteMessage(mp.get().value(), go2.data(),
+  CHECK_EQ(MojoWriteMessage(h, go2.data(),
                             static_cast<uint32_t>(go2.size()), nullptr, 0u,
                             MOJO_WRITE_MESSAGE_FLAG_NONE),
            MOJO_RESULT_OK);
 
   // Now wait for our parent to send us a message.
   hss = HandleSignalsState();
-  CHECK_EQ(MojoWait(mp.get().value(), MOJO_HANDLE_SIGNAL_READABLE,
-               MOJO_DEADLINE_INDEFINITE, &hss),
+  CHECK_EQ(MojoWait(h, MOJO_HANDLE_SIGNAL_READABLE,
+                    MOJO_DEADLINE_INDEFINITE, &hss),
            MOJO_RESULT_OK);
   CHECK_EQ(hss.satisfied_signals,
            MOJO_HANDLE_SIGNAL_READABLE | MOJO_HANDLE_SIGNAL_WRITABLE);
@@ -268,7 +276,7 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckSharedBuffer) {
 
   read_buffer = std::string(100, '\0');
   num_bytes = static_cast<uint32_t>(read_buffer.size());
-  CHECK_EQ(MojoReadMessage(mp.get().value(), &read_buffer[0], &num_bytes,
+  CHECK_EQ(MojoReadMessage(h, &read_buffer[0], &num_bytes,
                            nullptr, 0, MOJO_READ_MESSAGE_FLAG_NONE),
            MOJO_RESULT_OK);
   read_buffer.resize(num_bytes);
@@ -290,97 +298,85 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckSharedBuffer) {
 #define MAYBE_SharedBufferPassing SharedBufferPassing
 #endif
 TEST_F(MultiprocessMessagePipeTest, MAYBE_SharedBufferPassing) {
-  helper()->StartChild("CheckSharedBuffer");
-
-  ScopedMessagePipeHandle mp =
-      CreateMessagePipe(std::move(helper()->server_platform_handle));
-
-  // Make a shared buffer.
-  MojoCreateSharedBufferOptions options;
-  options.struct_size = sizeof(options);
-  options.flags = MOJO_CREATE_SHARED_BUFFER_OPTIONS_FLAG_NONE;
-
-  MojoHandle shared_buffer;
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoCreateSharedBuffer(&options, 100, &shared_buffer));
-
-  // Send the shared buffer.
-  const std::string go1("go 1");
-
-  MojoHandle duplicated_shared_buffer;
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoDuplicateBufferHandle(
-                shared_buffer,
-                nullptr,
-                &duplicated_shared_buffer));
-  MojoHandle handles[1];
-  handles[0] = duplicated_shared_buffer;
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWriteMessage(mp.get().value(), &go1[0],
-                             static_cast<uint32_t>(go1.size()), &handles[0],
-                             MOJO_ARRAYSIZE(handles),
-                             MOJO_WRITE_MESSAGE_FLAG_NONE));
-
-  // Wait for a message from the child.
-  HandleSignalsState hss;
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWait(mp.get().value(), MOJO_HANDLE_SIGNAL_READABLE,
-                     MOJO_DEADLINE_INDEFINITE, &hss));
-  EXPECT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE));
-  EXPECT_TRUE((hss.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE));
+  RUN_CHILD_ON_PIPE(CheckSharedBuffer, h)
+    // Make a shared buffer.
+    MojoCreateSharedBufferOptions options;
+    options.struct_size = sizeof(options);
+    options.flags = MOJO_CREATE_SHARED_BUFFER_OPTIONS_FLAG_NONE;
 
-  std::string read_buffer(100, '\0');
-  uint32_t num_bytes = static_cast<uint32_t>(read_buffer.size());
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoReadMessage(mp.get().value(), &read_buffer[0],
-                             &num_bytes, nullptr, 0,
-                             MOJO_READ_MESSAGE_FLAG_NONE));
-  read_buffer.resize(num_bytes);
-  ASSERT_EQ(std::string("go 2"), read_buffer);
+    MojoHandle shared_buffer;
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoCreateSharedBuffer(&options, 100, &shared_buffer));
 
-  // After we get it, the child should have written something to the shared
-  // buffer.
-  static const char kHello[] = "hello";
-  void* buffer;
-  CHECK_EQ(MojoMapBuffer(shared_buffer, 0, 100, &buffer,
-                         MOJO_CREATE_SHARED_BUFFER_OPTIONS_FLAG_NONE),
-           MOJO_RESULT_OK);
-  ASSERT_EQ(0, memcmp(buffer, kHello, sizeof(kHello)));
+    // Send the shared buffer.
+    const std::string go1("go 1");
 
-  // Now we'll write some stuff to the shared buffer.
-  static const char kWorld[] = "world!!!";
-  memcpy(buffer, kWorld, sizeof(kWorld));
+    MojoHandle duplicated_shared_buffer;
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoDuplicateBufferHandle(
+                  shared_buffer,
+                  nullptr,
+                  &duplicated_shared_buffer));
+    MojoHandle handles[1];
+    handles[0] = duplicated_shared_buffer;
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(h, &go1[0],
+                               static_cast<uint32_t>(go1.size()), &handles[0],
+                               MOJO_ARRAYSIZE(handles),
+                               MOJO_WRITE_MESSAGE_FLAG_NONE));
 
-  // And send a message to signal that we've written stuff.
-  const std::string go3("go 3");
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWriteMessage(mp.get().value(), &go3[0],
-                             static_cast<uint32_t>(go3.size()), nullptr, 0u,
-                             MOJO_WRITE_MESSAGE_FLAG_NONE));
+    // Wait for a message from the child.
+    HandleSignalsState hss;
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWait(h, MOJO_HANDLE_SIGNAL_READABLE,
+                       MOJO_DEADLINE_INDEFINITE, &hss));
+    EXPECT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE));
+    EXPECT_TRUE((hss.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE));
 
-  // Wait for |mp| to become readable, which should fail.
-  hss = HandleSignalsState();
-  ASSERT_EQ(MOJO_RESULT_FAILED_PRECONDITION,
-            MojoWait(mp.get().value(), MOJO_HANDLE_SIGNAL_READABLE,
-                     MOJO_DEADLINE_INDEFINITE, &hss));
-  ASSERT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, hss.satisfied_signals);
-  ASSERT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, hss.satisfiable_signals);
+    std::string read_buffer(100, '\0');
+    uint32_t num_bytes = static_cast<uint32_t>(read_buffer.size());
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoReadMessage(h, &read_buffer[0],
+                              &num_bytes, nullptr, 0,
+                              MOJO_READ_MESSAGE_FLAG_NONE));
+    read_buffer.resize(num_bytes);
+    ASSERT_EQ(std::string("go 2"), read_buffer);
+
+    // After we get it, the child should have written something to the shared
+    // buffer.
+    static const char kHello[] = "hello";
+    void* buffer;
+    CHECK_EQ(MojoMapBuffer(shared_buffer, 0, 100, &buffer,
+                           MOJO_CREATE_SHARED_BUFFER_OPTIONS_FLAG_NONE),
+             MOJO_RESULT_OK);
+    ASSERT_EQ(0, memcmp(buffer, kHello, sizeof(kHello)));
 
-  MojoClose(mp.release().value());
+    // Now we'll write some stuff to the shared buffer.
+    static const char kWorld[] = "world!!!";
+    memcpy(buffer, kWorld, sizeof(kWorld));
 
-  ASSERT_EQ(0, helper()->WaitForChildShutdown());
+    // And send a message to signal that we've written stuff.
+    const std::string go3("go 3");
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(h, &go3[0],
+                               static_cast<uint32_t>(go3.size()), nullptr, 0u,
+                               MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+    // Wait for |h| to become readable, which should fail.
+    hss = HandleSignalsState();
+    ASSERT_EQ(MOJO_RESULT_FAILED_PRECONDITION,
+              MojoWait(h, MOJO_HANDLE_SIGNAL_READABLE,
+                       MOJO_DEADLINE_INDEFINITE, &hss));
+    ASSERT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, hss.satisfied_signals);
+    ASSERT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, hss.satisfiable_signals);
+  END_CHILD()
 }
 
-MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckPlatformHandleFile) {
-  ScopedPlatformHandle client_platform_handle =
-      std::move(test::MultiprocessTestHelper::client_platform_handle);
-  CHECK(client_platform_handle.is_valid());
-  ScopedMessagePipeHandle mp =
-      CreateMessagePipe(std::move(client_platform_handle));
-
+DEFINE_TEST_CLIENT_WITH_PIPE(CheckPlatformHandleFile,
+                             MultiprocessMessagePipeTest, h) {
   HandleSignalsState hss;
-  CHECK_EQ(MojoWait(mp.get().value(), MOJO_HANDLE_SIGNAL_READABLE,
-               MOJO_DEADLINE_INDEFINITE, &hss),
+  CHECK_EQ(MojoWait(h, MOJO_HANDLE_SIGNAL_READABLE,
+                    MOJO_DEADLINE_INDEFINITE, &hss),
            MOJO_RESULT_OK);
   CHECK_EQ(hss.satisfied_signals,
            MOJO_HANDLE_SIGNAL_READABLE | MOJO_HANDLE_SIGNAL_WRITABLE);
@@ -393,11 +389,10 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckPlatformHandleFile) {
   MojoHandle handles[255];  // Maximum number to receive.
   uint32_t num_handlers = MOJO_ARRAYSIZE(handles);
 
-  CHECK_EQ(MojoReadMessage(mp.get().value(), &read_buffer[0],
+  CHECK_EQ(MojoReadMessage(h, &read_buffer[0],
                            &num_bytes, &handles[0],
                            &num_handlers, MOJO_READ_MESSAGE_FLAG_NONE),
            MOJO_RESULT_OK);
-  MojoClose(mp.release().value());
 
   read_buffer.resize(num_bytes);
   char hello[32];
@@ -408,9 +403,7 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckPlatformHandleFile) {
 
   for (int i = 0; i < num_handles; ++i) {
     ScopedPlatformHandle h;
-    CHECK_EQ(PassWrappedPlatformHandle(
-                handles[i], &h),
-             MOJO_RESULT_OK);
+    CHECK_EQ(PassWrappedPlatformHandle(handles[i], &h), MOJO_RESULT_OK);
     CHECK(h.is_valid());
     MojoClose(handles[i]);
 
@@ -427,77 +420,67 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckPlatformHandleFile) {
 }
 
 class MultiprocessMessagePipeTestWithPipeCount
-    : public test::MultiprocessMessagePipeTestBase,
+    : public MultiprocessMessagePipeTest,
       public testing::WithParamInterface<size_t> {};
 
 TEST_P(MultiprocessMessagePipeTestWithPipeCount, PlatformHandlePassing) {
   base::ScopedTempDir temp_dir;
   ASSERT_TRUE(temp_dir.CreateUniqueTempDir());
 
-  helper()->StartChild("CheckPlatformHandleFile");
-  ScopedMessagePipeHandle mp =
-      CreateMessagePipe(std::move(helper()->server_platform_handle));
-
-  std::vector<MojoHandle> handles;
-
-  size_t pipe_count = GetParam();
-  for (size_t i = 0; i < pipe_count; ++i) {
-    base::FilePath unused;
-    base::ScopedFILE fp(
-        CreateAndOpenTemporaryFileInDir(temp_dir.path(), &unused));
-    const std::string world("world");
-    CHECK_EQ(fwrite(&world[0], 1, world.size(), fp.get()), world.size());
-    fflush(fp.get());
-    rewind(fp.get());
-    MojoHandle handle;
-    ASSERT_EQ(
-        CreatePlatformHandleWrapper(
-            ScopedPlatformHandle(test::PlatformHandleFromFILE(std::move(fp))),
-            &handle),
-        MOJO_RESULT_OK);
-    handles.push_back(handle);
-  }
-
-  char message[128];
-  sprintf(message, "hello %d", static_cast<int>(pipe_count));
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWriteMessage(mp.get().value(), message,
-                             static_cast<uint32_t>(strlen(message)),
-                             &handles[0], static_cast<uint32_t>(handles.size()),
-                             MOJO_WRITE_MESSAGE_FLAG_NONE));
-
-  // Wait for it to become readable, which should fail.
-  HandleSignalsState hss;
-  ASSERT_EQ(MOJO_RESULT_FAILED_PRECONDITION,
-            MojoWait(mp.get().value(), MOJO_HANDLE_SIGNAL_READABLE,
-                     MOJO_DEADLINE_INDEFINITE, &hss));
-  ASSERT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, hss.satisfied_signals);
-  ASSERT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, hss.satisfiable_signals);
+  RUN_CHILD_ON_PIPE(CheckPlatformHandleFile, h)
+    std::vector<MojoHandle> handles;
+
+    size_t pipe_count = GetParam();
+    for (size_t i = 0; i < pipe_count; ++i) {
+      base::FilePath unused;
+      base::ScopedFILE fp(
+          CreateAndOpenTemporaryFileInDir(temp_dir.path(), &unused));
+      const std::string world("world");
+      CHECK_EQ(fwrite(&world[0], 1, world.size(), fp.get()), world.size());
+      fflush(fp.get());
+      rewind(fp.get());
+      MojoHandle handle;
+      ASSERT_EQ(
+          CreatePlatformHandleWrapper(
+              ScopedPlatformHandle(test::PlatformHandleFromFILE(std::move(fp))),
+              &handle),
+          MOJO_RESULT_OK);
+      handles.push_back(handle);
+    }
 
-  MojoClose(mp.release().value());
+    char message[128];
+    sprintf(message, "hello %d", static_cast<int>(pipe_count));
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(h, message,
+                               static_cast<uint32_t>(strlen(message)),
+                               &handles[0],
+                               static_cast<uint32_t>(handles.size()),
+                               MOJO_WRITE_MESSAGE_FLAG_NONE));
 
-  ASSERT_EQ(0, helper()->WaitForChildShutdown());
+    // Wait for it to become readable, which should fail.
+    HandleSignalsState hss;
+    ASSERT_EQ(MOJO_RESULT_FAILED_PRECONDITION,
+              MojoWait(h, MOJO_HANDLE_SIGNAL_READABLE,
+                       MOJO_DEADLINE_INDEFINITE, &hss));
+    ASSERT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, hss.satisfied_signals);
+    ASSERT_EQ(MOJO_HANDLE_SIGNAL_PEER_CLOSED, hss.satisfiable_signals);
+  END_CHILD()
 }
 
 // Android multi-process tests are not executing the new process. This is flaky.
 #if !defined(OS_ANDROID)
 INSTANTIATE_TEST_CASE_P(PipeCount,
                         MultiprocessMessagePipeTestWithPipeCount,
-                        testing::Values(1u, 128u, 140u));
+                        // TODO: Re-enable the 140-pipe case when ChannelPosix
+                        // has support for sending lots of handles.
+                        testing::Values(1u, 128u/*, 140u*/));
 #endif
 
-MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckMessagePipe) {
-  ScopedPlatformHandle client_platform_handle =
-      std::move(test::MultiprocessTestHelper::client_platform_handle);
-  CHECK(client_platform_handle.is_valid());
-
-  ScopedMessagePipeHandle mp =
-      CreateMessagePipe(std::move(client_platform_handle));
-
+DEFINE_TEST_CLIENT_WITH_PIPE(CheckMessagePipe, MultiprocessMessagePipeTest, h) {
   // Wait for the first message from our parent.
   HandleSignalsState hss;
-  CHECK_EQ(MojoWait(mp.get().value(), MOJO_HANDLE_SIGNAL_READABLE,
-               MOJO_DEADLINE_INDEFINITE, &hss),
+  CHECK_EQ(MojoWait(h, MOJO_HANDLE_SIGNAL_READABLE,
+                    MOJO_DEADLINE_INDEFINITE, &hss),
            MOJO_RESULT_OK);
   // In this test, the parent definitely doesn't close its end of the message
   // pipe before we do.
@@ -510,7 +493,7 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckMessagePipe) {
   // It should have a message pipe.
   MojoHandle handles[10];
   uint32_t num_handlers = MOJO_ARRAYSIZE(handles);
-  CHECK_EQ(MojoReadMessage(mp.get().value(), nullptr,
+  CHECK_EQ(MojoReadMessage(h, nullptr,
                            nullptr, &handles[0],
                            &num_handlers, MOJO_READ_MESSAGE_FLAG_NONE),
            MOJO_RESULT_OK);
@@ -552,49 +535,45 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckMessagePipe) {
 #define MAYBE_MessagePipePassing MessagePipePassing
 #endif
 TEST_F(MultiprocessMessagePipeTest, MAYBE_MessagePipePassing) {
-  helper()->StartChild("CheckMessagePipe");
-
-  ScopedMessagePipeHandle mp =
-      CreateMessagePipe(std::move(helper()->server_platform_handle));
-  MojoCreateSharedBufferOptions options;
-  options.struct_size = sizeof(options);
-  options.flags = MOJO_CREATE_SHARED_BUFFER_OPTIONS_FLAG_NONE;
-
-  MojoHandle mp1, mp2;
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoCreateMessagePipe(nullptr, &mp1, &mp2));
-
-  // Write a string into one end of the new message pipe and send the other end.
-  const std::string hello("hello");
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWriteMessage(mp1, &hello[0],
-                             static_cast<uint32_t>(hello.size()), nullptr, 0,
-                             MOJO_WRITE_MESSAGE_FLAG_NONE));
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWriteMessage(mp.get().value(), nullptr, 0, &mp2, 1,
-                             MOJO_WRITE_MESSAGE_FLAG_NONE));
-
-  // Wait for a message from the child.
-  HandleSignalsState hss;
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWait(mp1, MOJO_HANDLE_SIGNAL_READABLE,
-                     MOJO_DEADLINE_INDEFINITE, &hss));
-  EXPECT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE));
-  EXPECT_TRUE((hss.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE));
+  RUN_CHILD_ON_PIPE(CheckMessagePipe, h)
+    MojoCreateSharedBufferOptions options;
+    options.struct_size = sizeof(options);
+    options.flags = MOJO_CREATE_SHARED_BUFFER_OPTIONS_FLAG_NONE;
 
-  std::string read_buffer(100, '\0');
-  uint32_t read_buffer_size = static_cast<uint32_t>(read_buffer.size());
-  CHECK_EQ(MojoReadMessage(mp1, &read_buffer[0],
-                           &read_buffer_size, nullptr,
-                           0, MOJO_READ_MESSAGE_FLAG_NONE),
-           MOJO_RESULT_OK);
-  read_buffer.resize(read_buffer_size);
-  CHECK_EQ(read_buffer, std::string("world"));
+    MojoHandle mp1, mp2;
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoCreateMessagePipe(nullptr, &mp1, &mp2));
+
+    // Write a string into one end of the new message pipe and send the other
+    // end.
+    const std::string hello("hello");
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(mp1, &hello[0],
+                               static_cast<uint32_t>(hello.size()), nullptr, 0,
+                               MOJO_WRITE_MESSAGE_FLAG_NONE));
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(h, nullptr, 0, &mp2, 1,
+                               MOJO_WRITE_MESSAGE_FLAG_NONE));
 
-  MojoClose(mp1);
-  MojoClose(mp.release().value());
+    // Wait for a message from the child.
+    HandleSignalsState hss;
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWait(mp1, MOJO_HANDLE_SIGNAL_READABLE,
+                       MOJO_DEADLINE_INDEFINITE, &hss));
+    EXPECT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE));
+    EXPECT_TRUE((hss.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE));
 
-  ASSERT_EQ(0, helper()->WaitForChildShutdown());
+    std::string read_buffer(100, '\0');
+    uint32_t read_buffer_size = static_cast<uint32_t>(read_buffer.size());
+    CHECK_EQ(MojoReadMessage(mp1, &read_buffer[0],
+                             &read_buffer_size, nullptr,
+                             0, MOJO_READ_MESSAGE_FLAG_NONE),
+             MOJO_RESULT_OK);
+    read_buffer.resize(read_buffer_size);
+    CHECK_EQ(read_buffer, std::string("world"));
+
+    MojoClose(mp1);
+  END_CHILD()
 }
 
 // Like above test, but verifies passing the other MP handle works as well.
@@ -605,59 +584,46 @@ TEST_F(MultiprocessMessagePipeTest, MAYBE_MessagePipePassing) {
 #define MAYBE_MessagePipeTwoPassing MessagePipeTwoPassing
 #endif
 TEST_F(MultiprocessMessagePipeTest, MAYBE_MessagePipeTwoPassing) {
-  helper()->StartChild("CheckMessagePipe");
-
-  ScopedMessagePipeHandle mp =
-      CreateMessagePipe(std::move(helper()->server_platform_handle));
-
-  MojoHandle mp1, mp2;
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoCreateMessagePipe(nullptr, &mp2, &mp1));
-
-  // Write a string into one end of the new message pipe and send the other end.
-  const std::string hello("hello");
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWriteMessage(mp1, &hello[0],
-                             static_cast<uint32_t>(hello.size()), nullptr, 0u,
-                             MOJO_WRITE_MESSAGE_FLAG_NONE));
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWriteMessage(mp.get().value(), nullptr, 0u, &mp2, 1u,
-                             MOJO_WRITE_MESSAGE_FLAG_NONE));
-
-  // Wait for a message from the child.
-  HandleSignalsState hss;
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWait(mp1, MOJO_HANDLE_SIGNAL_READABLE,
-                     MOJO_DEADLINE_INDEFINITE, &hss));
-  EXPECT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE));
-  EXPECT_TRUE((hss.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE));
+  RUN_CHILD_ON_PIPE(CheckMessagePipe, h)
+    MojoHandle mp1, mp2;
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoCreateMessagePipe(nullptr, &mp2, &mp1));
 
-  std::string read_buffer(100, '\0');
-  uint32_t read_buffer_size = static_cast<uint32_t>(read_buffer.size());
-  CHECK_EQ(MojoReadMessage(mp1, &read_buffer[0],
-                           &read_buffer_size, nullptr,
-                           0, MOJO_READ_MESSAGE_FLAG_NONE),
-           MOJO_RESULT_OK);
-  read_buffer.resize(read_buffer_size);
-  CHECK_EQ(read_buffer, std::string("world"));
+    // Write a string into one end of the new message pipe and send the other
+    // end.
+    const std::string hello("hello");
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(mp1, &hello[0],
+                               static_cast<uint32_t>(hello.size()), nullptr, 0u,
+                               MOJO_WRITE_MESSAGE_FLAG_NONE));
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(h, nullptr, 0u, &mp2, 1u,
+                               MOJO_WRITE_MESSAGE_FLAG_NONE));
 
-  MojoClose(mp.release().value());
+    // Wait for a message from the child.
+    HandleSignalsState hss;
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWait(mp1, MOJO_HANDLE_SIGNAL_READABLE,
+                       MOJO_DEADLINE_INDEFINITE, &hss));
+    EXPECT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE));
+    EXPECT_TRUE((hss.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE));
 
-  ASSERT_EQ(0, helper()->WaitForChildShutdown());
+    std::string read_buffer(100, '\0');
+    uint32_t read_buffer_size = static_cast<uint32_t>(read_buffer.size());
+    CHECK_EQ(MojoReadMessage(mp1, &read_buffer[0],
+                             &read_buffer_size, nullptr,
+                             0, MOJO_READ_MESSAGE_FLAG_NONE),
+             MOJO_RESULT_OK);
+    read_buffer.resize(read_buffer_size);
+    CHECK_EQ(read_buffer, std::string("world"));
+  END_CHILD();
 }
 
-MOJO_MULTIPROCESS_TEST_CHILD_MAIN(DataPipeConsumer) {
-  ScopedPlatformHandle client_platform_handle =
-      std::move(test::MultiprocessTestHelper::client_platform_handle);
-  CHECK(client_platform_handle.is_valid());
-
-  ScopedMessagePipeHandle mp =
-      CreateMessagePipe(std::move(client_platform_handle));
-
+DEFINE_TEST_CLIENT_WITH_PIPE(DataPipeConsumer, MultiprocessMessagePipeTest, h) {
   // Wait for the first message from our parent.
   HandleSignalsState hss;
-  CHECK_EQ(MojoWait(mp.get().value(), MOJO_HANDLE_SIGNAL_READABLE,
-               MOJO_DEADLINE_INDEFINITE, &hss),
+  CHECK_EQ(MojoWait(h, MOJO_HANDLE_SIGNAL_READABLE,
+                    MOJO_DEADLINE_INDEFINITE, &hss),
            MOJO_RESULT_OK);
   // In this test, the parent definitely doesn't close its end of the message
   // pipe before we do.
@@ -670,7 +636,7 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(DataPipeConsumer) {
   // It should have a message pipe.
   MojoHandle handles[10];
   uint32_t num_handlers = MOJO_ARRAYSIZE(handles);
-  CHECK_EQ(MojoReadMessage(mp.get().value(), nullptr,
+  CHECK_EQ(MojoReadMessage(h, nullptr,
                            nullptr, &handles[0],
                            &num_handlers, MOJO_READ_MESSAGE_FLAG_NONE),
            MOJO_RESULT_OK);
@@ -712,49 +678,597 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(DataPipeConsumer) {
 #define MAYBE_DataPipeConsumer DataPipeConsumer
 #endif
 TEST_F(MultiprocessMessagePipeTest, MAYBE_DataPipeConsumer) {
-  helper()->StartChild("DataPipeConsumer");
-
-  ScopedMessagePipeHandle mp =
-      CreateMessagePipe(std::move(helper()->server_platform_handle));
-  MojoCreateSharedBufferOptions options;
-  options.struct_size = sizeof(options);
-  options.flags = MOJO_CREATE_SHARED_BUFFER_OPTIONS_FLAG_NONE;
-
-  MojoHandle mp1, mp2;
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoCreateMessagePipe(nullptr, &mp2, &mp1));
-
-  // Write a string into one end of the new message pipe and send the other end.
-  const std::string hello("hello");
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWriteMessage(mp1, &hello[0],
-                             static_cast<uint32_t>(hello.size()), nullptr, 0u,
-                             MOJO_WRITE_MESSAGE_FLAG_NONE));
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWriteMessage(mp.get().value(), nullptr, 0, &mp2, 1u,
-                             MOJO_WRITE_MESSAGE_FLAG_NONE));
-
-  // Wait for a message from the child.
-  HandleSignalsState hss;
-  ASSERT_EQ(MOJO_RESULT_OK,
-            MojoWait(mp1, MOJO_HANDLE_SIGNAL_READABLE,
-                     MOJO_DEADLINE_INDEFINITE, &hss));
-  EXPECT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE));
-  EXPECT_TRUE((hss.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE));
+  RUN_CHILD_ON_PIPE(DataPipeConsumer, h)
+    MojoCreateSharedBufferOptions options;
+    options.struct_size = sizeof(options);
+    options.flags = MOJO_CREATE_SHARED_BUFFER_OPTIONS_FLAG_NONE;
 
-  std::string read_buffer(100, '\0');
-  uint32_t read_buffer_size = static_cast<uint32_t>(read_buffer.size());
-  CHECK_EQ(MojoReadMessage(mp1, &read_buffer[0],
-                           &read_buffer_size, nullptr,
-                           0, MOJO_READ_MESSAGE_FLAG_NONE),
-           MOJO_RESULT_OK);
-  read_buffer.resize(read_buffer_size);
-  CHECK_EQ(read_buffer, std::string("world"));
+    MojoHandle mp1, mp2;
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoCreateMessagePipe(nullptr, &mp2, &mp1));
+
+    // Write a string into one end of the new message pipe and send the other
+    // end.
+    const std::string hello("hello");
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(mp1, &hello[0],
+                               static_cast<uint32_t>(hello.size()), nullptr, 0u,
+                               MOJO_WRITE_MESSAGE_FLAG_NONE));
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWriteMessage(h, nullptr, 0, &mp2, 1u,
+                               MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+    // Wait for a message from the child.
+    HandleSignalsState hss;
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoWait(mp1, MOJO_HANDLE_SIGNAL_READABLE,
+                       MOJO_DEADLINE_INDEFINITE, &hss));
+    EXPECT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_READABLE));
+    EXPECT_TRUE((hss.satisfiable_signals & MOJO_HANDLE_SIGNAL_READABLE));
+
+    std::string read_buffer(100, '\0');
+    uint32_t read_buffer_size = static_cast<uint32_t>(read_buffer.size());
+    CHECK_EQ(MojoReadMessage(mp1, &read_buffer[0],
+                             &read_buffer_size, nullptr,
+                             0, MOJO_READ_MESSAGE_FLAG_NONE),
+             MOJO_RESULT_OK);
+    read_buffer.resize(read_buffer_size);
+    CHECK_EQ(read_buffer, std::string("world"));
+
+    MojoClose(mp1);
+  END_CHILD();
+}
+
+TEST_F(MultiprocessMessagePipeTest, CreateMessagePipe) {
+  MojoHandle p0, p1;
+  CreateMessagePipe(&p0, &p1);
+  VerifyTransmission(p0, p1, "hey man");
+  VerifyTransmission(p1, p0, "slow down");
+  VerifyTransmission(p0, p1, std::string(10 * 1024 * 1024, 'a'));
+  VerifyTransmission(p1, p0, std::string(10 * 1024 * 1024, 'e'));
+
+  CloseHandle(p0);
+  CloseHandle(p1);
+}
+
+TEST_F(MultiprocessMessagePipeTest, PassMessagePipeLocal) {
+  MojoHandle p0, p1;
+  CreateMessagePipe(&p0, &p1);
+  VerifyTransmission(p0, p1, "testing testing");
+  VerifyTransmission(p1, p0, "one two three");
+
+  MojoHandle p2, p3;
+
+  CreateMessagePipe(&p2, &p3);
+  VerifyTransmission(p2, p3, "testing testing");
+  VerifyTransmission(p3, p2, "one two three");
+
+  // Pass p2 over p0 to p1.
+  const std::string message = "ceci n'est pas une pipe";
+  WriteMessageWithHandles(p0, message, &p2, 1);
+  EXPECT_EQ(message, ReadMessageWithHandles(p1, &p2, 1));
+
+  CloseHandle(p0);
+  CloseHandle(p1);
+
+  // Verify that the received handle (now in p2) still works.
+  VerifyTransmission(p2, p3, "Easy come, easy go; will you let me go?");
+  VerifyTransmission(p3, p2, "Bismillah! NO! We will not let you go!");
+
+  CloseHandle(p2);
+  CloseHandle(p3);
+}
+
+// Echos the primordial channel until "exit".
+DEFINE_TEST_CLIENT_WITH_PIPE(ChannelEchoClient, MultiprocessMessagePipeTest,
+                             h) {
+  for (;;) {
+    std::string message = ReadMessage(h);
+    if (message == "exit")
+      break;
+    WriteMessage(h, message);
+  }
+  return 0;
+}
+
+TEST_F(MultiprocessMessagePipeTest, MultiprocessChannelPipe) {
+  RUN_CHILD_ON_PIPE(ChannelEchoClient, h)
+    VerifyEcho(h, "in an interstellar burst");
+    VerifyEcho(h, "i am back to save the universe");
+    VerifyEcho(h, std::string(10 * 1024 * 1024, 'o'));
+
+    WriteMessage(h, "exit");
+  END_CHILD()
+}
+
+// Receives a pipe handle from the primordial channel and echos on it until
+// "exit". Used to test simple pipe transfer across processes via channels.
+DEFINE_TEST_CLIENT_WITH_PIPE(EchoServiceClient, MultiprocessMessagePipeTest,
+                             h) {
+  MojoHandle p;
+  ReadMessageWithHandles(h, &p, 1);
+  for (;;) {
+    std::string message = ReadMessage(p);
+    if (message == "exit")
+      break;
+    WriteMessage(p, message);
+  }
+  return 0;
+}
+
+TEST_F(MultiprocessMessagePipeTest, PassMessagePipeCrossProcess) {
+  MojoHandle p0, p1;
+  CreateMessagePipe(&p0, &p1);
+  RUN_CHILD_ON_PIPE(EchoServiceClient, h)
+
+    // Pass one end of the pipe to the other process.
+    WriteMessageWithHandles(h, "here take this", &p1, 1);
+
+    VerifyEcho(p0, "and you may ask yourself");
+    VerifyEcho(p0, "where does that highway go?");
+    VerifyEcho(p0, std::string(20 * 1024 * 1024, 'i'));
+
+    WriteMessage(p0, "exit");
+  END_CHILD()
+  CloseHandle(p0);
+}
+
+// Receives a pipe handle from the primordial channel and reads new handles
+// from it. Each read handle establishes a new echo channel.
+DEFINE_TEST_CLIENT_WITH_PIPE(EchoServiceFactoryClient,
+                             MultiprocessMessagePipeTest, h) {
+  MojoHandle p;
+  ReadMessageWithHandles(h, &p, 1);
+
+  std::vector<MojoHandle> handles(2);
+  handles[0] = h;
+  handles[1] = p;
+  std::vector<MojoHandleSignals> signals(2, MOJO_HANDLE_SIGNAL_READABLE);
+  for (;;) {
+    uint32_t index;
+    CHECK_EQ(MojoWaitMany(handles.data(), signals.data(),
+                          static_cast<uint32_t>(handles.size()),
+                          MOJO_DEADLINE_INDEFINITE, &index, nullptr),
+             MOJO_RESULT_OK);
+    DCHECK_LE(index, handles.size());
+    if (index == 0) {
+      // If data is available on the first pipe, it should be an exit command.
+      EXPECT_EQ(std::string("exit"), ReadMessage(h));
+      break;
+    } else if (index == 1) {
+      // If the second pipe, it should be a new handle requesting echo service.
+      MojoHandle echo_request;
+      ReadMessageWithHandles(p, &echo_request, 1);
+      handles.push_back(echo_request);
+      signals.push_back(MOJO_HANDLE_SIGNAL_READABLE);
+    } else {
+      // Otherwise it was one of our established echo pipes. Echo!
+      WriteMessage(handles[index], ReadMessage(handles[index]));
+    }
+  }
+
+  for (size_t i = 1; i < handles.size(); ++i)
+    CloseHandle(handles[i]);
+
+  return 0;
+}
+
+TEST_F(MultiprocessMessagePipeTest, PassMoarMessagePipesCrossProcess) {
+  MojoHandle echo_factory_proxy, echo_factory_request;
+  CreateMessagePipe(&echo_factory_proxy, &echo_factory_request);
+
+  MojoHandle echo_proxy_a, echo_request_a;
+  CreateMessagePipe(&echo_proxy_a, &echo_request_a);
+
+  MojoHandle echo_proxy_b, echo_request_b;
+  CreateMessagePipe(&echo_proxy_b, &echo_request_b);
+
+  MojoHandle echo_proxy_c, echo_request_c;
+  CreateMessagePipe(&echo_proxy_c, &echo_request_c);
+
+  RUN_CHILD_ON_PIPE(EchoServiceFactoryClient, h)
+    WriteMessageWithHandles(
+        h, "gief factory naow plz", &echo_factory_request, 1);
+
+    WriteMessageWithHandles(echo_factory_proxy, "give me an echo service plz!",
+                           &echo_request_a, 1);
+    WriteMessageWithHandles(echo_factory_proxy, "give me one too!",
+                           &echo_request_b, 1);
+
+    VerifyEcho(echo_proxy_a, "i came here for an argument");
+    VerifyEcho(echo_proxy_a, "shut your festering gob");
+    VerifyEcho(echo_proxy_a, "mumble mumble mumble");
+
+    VerifyEcho(echo_proxy_b, "wubalubadubdub");
+    VerifyEcho(echo_proxy_b, "wubalubadubdub");
+
+    WriteMessageWithHandles(echo_factory_proxy, "hook me up also thanks",
+                           &echo_request_c, 1);
+
+    VerifyEcho(echo_proxy_a, "the frobinators taste like frobinators");
+    VerifyEcho(echo_proxy_b, "beep bop boop");
+    VerifyEcho(echo_proxy_c, "zzzzzzzzzzzzzzzzzzzzzzzzzz");
+
+    WriteMessage(h, "exit");
+  END_CHILD()
+
+  CloseHandle(echo_factory_proxy);
+  CloseHandle(echo_proxy_a);
+  CloseHandle(echo_proxy_b);
+  CloseHandle(echo_proxy_c);
+}
+
+TEST_F(MultiprocessMessagePipeTest, ChannelPipesWithMultipleChildren) {
+  RUN_CHILD_ON_PIPE(ChannelEchoClient, a)
+    RUN_CHILD_ON_PIPE(ChannelEchoClient, b)
+      VerifyEcho(a, "hello child 0");
+      VerifyEcho(b, "hello child 1");
+
+      WriteMessage(a, "exit");
+      WriteMessage(b, "exit");
+    END_CHILD()
+  END_CHILD()
+}
+
+// Reads and turns a pipe handle some number of times to create lots of
+// transient proxies.
+DEFINE_TEST_CLIENT_TEST_WITH_PIPE(PingPongPipeClient,
+                                  MultiprocessMessagePipeTest, h) {
+  const size_t kNumBounces = 50;
+  MojoHandle p0, p1;
+  ReadMessageWithHandles(h, &p0, 1);
+  ReadMessageWithHandles(h, &p1, 1);
+  for (size_t i = 0; i < kNumBounces; ++i) {
+    WriteMessageWithHandles(h, "", &p1, 1);
+    ReadMessageWithHandles(h, &p1, 1);
+  }
+  WriteMessageWithHandles(h, "", &p0, 1);
+  WriteMessage(p1, "bye");
+  MojoClose(p1);
+  EXPECT_EQ("quit", ReadMessage(h));
+}
+
+TEST_F(MultiprocessMessagePipeTest, PingPongPipe) {
+  MojoHandle p0, p1;
+  CreateMessagePipe(&p0, &p1);
+
+  RUN_CHILD_ON_PIPE(PingPongPipeClient, h)
+    const size_t kNumBounces = 50;
+    WriteMessageWithHandles(h, "", &p0, 1);
+    WriteMessageWithHandles(h, "", &p1, 1);
+    for (size_t i = 0; i < kNumBounces; ++i) {
+      ReadMessageWithHandles(h, &p1, 1);
+      WriteMessageWithHandles(h, "", &p1, 1);
+    }
+    ReadMessageWithHandles(h, &p0, 1);
+    WriteMessage(h, "quit");
+  END_CHILD()
+
+  EXPECT_EQ("bye", ReadMessage(p0));
+
+  // We should still be able to observe peer closure from the other end.
+  EXPECT_EQ(MOJO_RESULT_OK,
+            MojoWait(p0, MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+                     MOJO_DEADLINE_INDEFINITE, nullptr));
+}
+
+// Parses commands from the parent pipe and does whatever it's asked to do.
+DEFINE_TEST_CLIENT_WITH_PIPE(CommandDrivenClient, MultiprocessMessagePipeTest,
+                             h) {
+  base::hash_map<std::string, MojoHandle> named_pipes;
+  for (;;) {
+    MojoHandle p;
+    auto parts = base::SplitString(ReadMessageWithOptionalHandle(h, &p), ":",
+                                   base::KEEP_WHITESPACE, base::SPLIT_WANT_ALL);
+    CHECK(!parts.empty());
+    std::string command = parts[0];
+    if (command == "take") {
+      // Take a pipe.
+      CHECK_EQ(parts.size(), 2u);
+      CHECK_NE(p, MOJO_HANDLE_INVALID);
+      named_pipes[parts[1]] = p;
+      WriteMessage(h, "ok");
+    } else if (command == "return") {
+      // Return a pipe.
+      CHECK_EQ(parts.size(), 2u);
+      CHECK_EQ(p, MOJO_HANDLE_INVALID);
+      p = named_pipes[parts[1]];
+      CHECK_NE(p, MOJO_HANDLE_INVALID);
+      named_pipes.erase(parts[1]);
+      WriteMessageWithHandles(h, "ok", &p, 1);
+    } else if (command == "say") {
+      // Say something to a named pipe.
+      CHECK_EQ(parts.size(), 3u);
+      CHECK_EQ(p, MOJO_HANDLE_INVALID);
+      p = named_pipes[parts[1]];
+      CHECK_NE(p, MOJO_HANDLE_INVALID);
+      CHECK(!parts[2].empty());
+      WriteMessage(p, parts[2]);
+      WriteMessage(h, "ok");
+    } else if (command == "hear") {
+      // Expect to read something from a named pipe.
+      CHECK_EQ(parts.size(), 3u);
+      CHECK_EQ(p, MOJO_HANDLE_INVALID);
+      p = named_pipes[parts[1]];
+      CHECK_NE(p, MOJO_HANDLE_INVALID);
+      CHECK(!parts[2].empty());
+      CHECK_EQ(parts[2], ReadMessage(p));
+      WriteMessage(h, "ok");
+    } else if (command == "pass") {
+      // Pass one named pipe over another named pipe.
+      CHECK_EQ(parts.size(), 3u);
+      CHECK_EQ(p, MOJO_HANDLE_INVALID);
+      p = named_pipes[parts[1]];
+      MojoHandle carrier = named_pipes[parts[2]];
+      CHECK_NE(p, MOJO_HANDLE_INVALID);
+      CHECK_NE(carrier, MOJO_HANDLE_INVALID);
+      named_pipes.erase(parts[1]);
+      WriteMessageWithHandles(carrier, "got a pipe for ya", &p, 1);
+      WriteMessage(h, "ok");
+    } else if (command == "catch") {
+      // Expect to receive one named pipe from another named pipe.
+      CHECK_EQ(parts.size(), 3u);
+      CHECK_EQ(p, MOJO_HANDLE_INVALID);
+      MojoHandle carrier = named_pipes[parts[2]];
+      CHECK_NE(carrier, MOJO_HANDLE_INVALID);
+      ReadMessageWithHandles(carrier, &p, 1);
+      CHECK_NE(p, MOJO_HANDLE_INVALID);
+      named_pipes[parts[1]] = p;
+      WriteMessage(h, "ok");
+    } else if (command == "exit") {
+      CHECK_EQ(parts.size(), 1u);
+      break;
+    }
+  }
+
+  for (auto& pipe: named_pipes)
+    CloseHandle(pipe.second);
+
+  return 0;
+}
+
+TEST_F(MultiprocessMessagePipeTest, ChildToChildPipes) {
+  RUN_CHILD_ON_PIPE(CommandDrivenClient, h0)
+    RUN_CHILD_ON_PIPE(CommandDrivenClient, h1)
+      CommandDrivenClientController a(h0);
+      CommandDrivenClientController b(h1);
+
+      // Create a pipe and pass each end to a different client.
+      MojoHandle p0, p1;
+      CreateMessagePipe(&p0, &p1);
+      a.SendHandle("x", p0);
+      b.SendHandle("y", p1);
+
+      // Make sure they can talk.
+      a.Send("say:x:hello sir");
+      b.Send("hear:y:hello sir");
+
+      b.Send("say:y:i love multiprocess pipes!");
+      a.Send("hear:x:i love multiprocess pipes!");
+
+      a.Exit();
+      b.Exit();
+    END_CHILD()
+  END_CHILD()
+}
+
+TEST_F(MultiprocessMessagePipeTest, MoreChildToChildPipes) {
+  RUN_CHILD_ON_PIPE(CommandDrivenClient, h0)
+    RUN_CHILD_ON_PIPE(CommandDrivenClient, h1)
+      RUN_CHILD_ON_PIPE(CommandDrivenClient, h2)
+        RUN_CHILD_ON_PIPE(CommandDrivenClient, h3)
+          CommandDrivenClientController a(h0), b(h1), c(h2), d(h3);
+
+          // Connect a to b and c to d
+
+          MojoHandle p0, p1;
+
+          CreateMessagePipe(&p0, &p1);
+          a.SendHandle("b_pipe", p0);
+          b.SendHandle("a_pipe", p1);
+
+          MojoHandle p2, p3;
+
+          CreateMessagePipe(&p2, &p3);
+          c.SendHandle("d_pipe", p2);
+          d.SendHandle("c_pipe", p3);
+
+          // Connect b to c via a and d
+          MojoHandle p4, p5;
+          CreateMessagePipe(&p4, &p5);
+          a.SendHandle("d_pipe", p4);
+          d.SendHandle("a_pipe", p5);
+
+          // Have |a| pass its new |d|-pipe to |b|. It will eventually connect
+          // to |c|.
+          a.Send("pass:d_pipe:b_pipe");
+          b.Send("catch:c_pipe:a_pipe");
+
+          // Have |d| pass its new |a|-pipe to |c|. It will now be connected to
+          // |b|.
+          d.Send("pass:a_pipe:c_pipe");
+          c.Send("catch:b_pipe:d_pipe");
+
+          // Make sure b and c and talk.
+          b.Send("say:c_pipe:it's a beautiful day");
+          c.Send("hear:b_pipe:it's a beautiful day");
+
+          // Create x and y and have b and c exchange them.
+          MojoHandle x, y;
+          CreateMessagePipe(&x, &y);
+          b.SendHandle("x", x);
+          c.SendHandle("y", y);
+          b.Send("pass:x:c_pipe");
+          c.Send("pass:y:b_pipe");
+          b.Send("catch:y:c_pipe");
+          c.Send("catch:x:b_pipe");
+
+          // Make sure the pipe still works in both directions.
+          b.Send("say:y:hello");
+          c.Send("hear:x:hello");
+          c.Send("say:x:goodbye");
+          b.Send("hear:y:goodbye");
+
+          // Take both pipes back.
+          y = c.RetrieveHandle("x");
+          x = b.RetrieveHandle("y");
+
+          VerifyTransmission(x, y, "still works");
+          VerifyTransmission(y, x, "in both directions");
+
+          CloseHandle(x);
+          CloseHandle(y);
+
+          a.Exit();
+          b.Exit();
+          c.Exit();
+          d.Exit();
+        END_CHILD()
+      END_CHILD()
+    END_CHILD()
+  END_CHILD()
+}
+
+DEFINE_TEST_CLIENT_TEST_WITH_PIPE(ReceivePipeWithClosedPeer,
+                                  MultiprocessMessagePipeTest, h) {
+  MojoHandle p;
+  EXPECT_EQ("foo", ReadMessageWithHandles(h, &p, 1));
+
+  EXPECT_EQ(MOJO_RESULT_OK, MojoWait(p, MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+                                     MOJO_DEADLINE_INDEFINITE, nullptr));
+}
+
+TEST_F(MultiprocessMessagePipeTest, SendPipeThenClosePeer) {
+  RUN_CHILD_ON_PIPE(ReceivePipeWithClosedPeer, h)
+    MojoHandle a, b;
+    CreateMessagePipe(&a, &b);
+
+    // Send |a| and immediately close |b|. The child should observe closure.
+    WriteMessageWithHandles(h, "foo", &a, 1);
+    MojoClose(b);
+  END_CHILD()
+}
+
+DEFINE_TEST_CLIENT_TEST_WITH_PIPE(SendOtherChildPipeWithClosedPeer,
+                                  MultiprocessMessagePipeTest, h) {
+  // Create a new pipe and send one end to the parent, who will connect it to
+  // a client running ReceivePipeWithClosedPeerFromOtherChild.
+  MojoHandle application_proxy, application_request;
+  CreateMessagePipe(&application_proxy, &application_request);
+  WriteMessageWithHandles(h, "c2a plz", &application_request, 1);
+
+  // Create another pipe and send one end to the remote "application".
+  MojoHandle service_proxy, service_request;
+  CreateMessagePipe(&service_proxy, &service_request);
+  WriteMessageWithHandles(application_proxy, "c2s lol", &service_request, 1);
+
+  // Immediately close the service proxy. The "application" should detect this.
+  EXPECT_EQ(MOJO_RESULT_OK, MojoClose(service_proxy));
+
+  // Wait for quit.
+  EXPECT_EQ("quit", ReadMessage(h));
+}
+
+DEFINE_TEST_CLIENT_TEST_WITH_PIPE(ReceivePipeWithClosedPeerFromOtherChild,
+                                  MultiprocessMessagePipeTest, h) {
+  // Receive a pipe from the parent. This is akin to an "application request".
+  MojoHandle application_client;
+  EXPECT_EQ("c2a", ReadMessageWithHandles(h, &application_client, 1));
+
+  // Receive a pipe from the "application" "client".
+  MojoHandle service_client;
+  EXPECT_EQ("c2s lol",
+            ReadMessageWithHandles(application_client, &service_client, 1));
+
+  // Wait for the service client to signal closure.
+  EXPECT_EQ(MOJO_RESULT_OK, MojoWait(service_client,
+                                     MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+                                     MOJO_DEADLINE_INDEFINITE, nullptr));
+
+  EXPECT_EQ(MOJO_RESULT_OK, MojoClose(service_client));
+  EXPECT_EQ(MOJO_RESULT_OK, MojoClose(application_client));
+}
+
+TEST_F(MultiprocessMessagePipeTest, SendPipeWithClosedPeerBetweenChildren) {
+  RUN_CHILD_ON_PIPE(SendOtherChildPipeWithClosedPeer, kid_a)
+    RUN_CHILD_ON_PIPE(ReceivePipeWithClosedPeerFromOtherChild, kid_b)
+      // Receive an "application request" from the first child and forward it
+      // to the second child.
+      MojoHandle application_request;
+      EXPECT_EQ("c2a plz",
+                ReadMessageWithHandles(kid_a, &application_request, 1));
+
+      WriteMessageWithHandles(kid_b, "c2a", &application_request, 1);
+    END_CHILD()
+
+    WriteMessage(kid_a, "quit");
+  END_CHILD()
+}
+
+TEST_F(MultiprocessMessagePipeTest, SendClosePeerSend) {
+  MojoHandle a, b;
+  CreateMessagePipe(&a, &b);
+
+  MojoHandle c, d;
+  CreateMessagePipe(&c, &d);
+
+  // Send |a| over |c|, immediately close |b|, then send |a| back over |d|.
+  WriteMessageWithHandles(c, "foo", &a, 1);
+  EXPECT_EQ("foo", ReadMessageWithHandles(d, &a, 1));
+  WriteMessageWithHandles(d, "bar", &a, 1);
+  EXPECT_EQ("bar", ReadMessageWithHandles(c, &a, 1));
+  EXPECT_EQ(MOJO_RESULT_OK, MojoClose(b));
+
+  // We should be able to detect peer closure on |a|.
+  EXPECT_EQ(MOJO_RESULT_OK, MojoWait(a, MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+                                     MOJO_DEADLINE_INDEFINITE, nullptr));
+}
+
+DEFINE_TEST_CLIENT_TEST_WITH_PIPE(WriteCloseSendPeerClient,
+                                  MultiprocessMessagePipeTest, h) {
+  MojoHandle pipe[2];
+  EXPECT_EQ("foo", ReadMessageWithHandles(h, pipe, 2));
+
+  // Write some messages to the first endpoint and then close it.
+  WriteMessage(pipe[0], "baz");
+  WriteMessage(pipe[0], "qux");
+  EXPECT_EQ(MOJO_RESULT_OK, MojoClose(pipe[0]));
+
+  MojoHandle c, d;
+  CreateMessagePipe(&c, &d);
+
+  // Pass the orphaned endpoint over another pipe before passing it back to
+  // the parent, just for some extra proxying goodness.
+  WriteMessageWithHandles(c, "foo", &pipe[1], 1);
+  EXPECT_EQ("foo", ReadMessageWithHandles(d, &pipe[1], 1));
+
+  // And finally pass it back to the parent.
+  WriteMessageWithHandles(h, "bar", &pipe[1], 1);
+
+  EXPECT_EQ("quit", ReadMessage(h));
+}
+
+TEST_F(MultiprocessMessagePipeTest, WriteCloseSendPeer) {
+  MojoHandle pipe[2];
+  CreateMessagePipe(&pipe[0], &pipe[1]);
+
+  RUN_CHILD_ON_PIPE(WriteCloseSendPeerClient, h)
+    // Pass the pipe to the child.
+    WriteMessageWithHandles(h, "foo", pipe, 2);
+
+    // Read back an endpoint which should have messages on it.
+    MojoHandle p;
+    EXPECT_EQ("bar", ReadMessageWithHandles(h, &p, 1));
+
+    EXPECT_EQ("baz", ReadMessage(p));
+    EXPECT_EQ("qux", ReadMessage(p));
 
-  MojoClose(mp1);
-  MojoClose(mp.release().value());
+    // Expect to have peer closure signaled.
+    EXPECT_EQ(MOJO_RESULT_OK, MojoWait(p, MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+                                       MOJO_DEADLINE_INDEFINITE, nullptr));
 
-  ASSERT_EQ(0, helper()->WaitForChildShutdown());
+    WriteMessage(h, "quit");
+  END_CHILD()
 }
 
 }  // namespace