Add multiprocess test helper functions.

Don't force people who want to write multiprocess tests to derive their
test fixture from MultiProcessTest.

TBR=phajdan.jr@chromium.org

Review URL: https://codereview.chromium.org/189373002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255796 0039d316-1c4b-4281-b951-d872f2087c98

base/test/multiprocess_test.cc

@@ -9,6 +9,34 @@
 
 namespace base {
 
+#if !defined(OS_ANDROID)
+ProcessHandle SpawnMultiProcessTestChild(
+    const std::string& procname,
+    const CommandLine& base_command_line,
+    const LaunchOptions& options,
+    bool debug_on_start) {
+  CommandLine command_line(base_command_line);
+  // TODO(viettrungluu): See comment above |MakeCmdLine()| in the header file.
+  // This is a temporary hack, since |MakeCmdLine()| has to provide a full
+  // command line.
+  if (!command_line.HasSwitch(switches::kTestChildProcess)) {
+    command_line.AppendSwitchASCII(switches::kTestChildProcess, procname);
+    if (debug_on_start)
+      command_line.AppendSwitch(switches::kDebugOnStart);
+  }
+
+  ProcessHandle handle = kNullProcessHandle;
+  LaunchProcess(command_line, options, &handle);
+  return handle;
+}
+#endif  // !defined(OS_ANDROID)
+
+CommandLine GetMultiProcessTestChildBaseCommandLine() {
+  return *CommandLine::ForCurrentProcess();
+}
+
+// MultiProcessTest ------------------------------------------------------------
+
 MultiProcessTest::MultiProcessTest() {
 }
 
@@ -21,24 +49,23 @@ ProcessHandle MultiProcessTest::SpawnChild(const std::string& procname,
   return SpawnChildWithOptions(procname, options, debug_on_start);
 }
 
-#if !defined(OS_ANDROID)
 ProcessHandle MultiProcessTest::SpawnChildWithOptions(
     const std::string& procname,
     const LaunchOptions& options,
     bool debug_on_start) {
-  ProcessHandle handle = kNullProcessHandle;
-  LaunchProcess(MakeCmdLine(procname, debug_on_start), options, &handle);
-  return handle;
+  return SpawnMultiProcessTestChild(procname,
+                                    MakeCmdLine(procname, debug_on_start),
+                                    options,
+                                    debug_on_start);
 }
-#endif
 
 CommandLine MultiProcessTest::MakeCmdLine(const std::string& procname,
                                           bool debug_on_start) {
-  CommandLine cl(*CommandLine::ForCurrentProcess());
-  cl.AppendSwitchASCII(switches::kTestChildProcess, procname);
+  CommandLine command_line = GetMultiProcessTestChildBaseCommandLine();
+  command_line.AppendSwitchASCII(switches::kTestChildProcess, procname);
   if (debug_on_start)
-    cl.AppendSwitch(switches::kDebugOnStart);
-  return cl;
+    command_line.AppendSwitch(switches::kDebugOnStart);
+  return command_line;
 }
 
 }  // namespace base

base/test/multiprocess_test.h

@@ -17,6 +17,59 @@ class CommandLine;
 
 namespace base {
 
+// Helpers to spawn a child for a multiprocess test and execute a designated
+// function. Use these when you already have another base class for your test
+// fixture, but you want (some) of your tests to be multiprocess (otherwise you
+// may just want to derive your fixture from |MultiProcessTest|, below).
+//
+// Use these helpers as follows:
+//
+//   TEST_F(MyTest, ATest) {
+//     CommandLine command_line(
+//         base::GetMultiProcessTestChildBaseCommandLine());
+//     // Maybe add our own switches to |command_line|....
+//
+//     LaunchOptions options;
+//     // Maybe set some options (e.g., |start_hidden| on Windows)....
+//
+//     // Start a child process and run |a_test_func|.
+//     base::ProcessHandle test_child_handle =
+//         base::SpawnMultiProcessTestChild("a_test_func", command_line,
+//                                          options, false);
+//
+//     // Do stuff involving |test_child_handle| and the child process....
+//
+//     int rv = -1;
+//     ASSERT_TRUE(base::WaitForExitCodeWithTimeout(
+//         test_child_handle, &rv, TestTimeouts::action_timeout()));
+//     base::CloseProcessHandle(test_child_handle);
+//     EXPECT_EQ(0, rv);
+//   }
+//
+//   // Note: |MULTIPROCESS_TEST_MAIN()| is defined in
+//   // testing/multi_process_function_list.h.
+//   MULTIPROCESS_TEST_MAIN(a_test_func) {
+//     // Code here runs in a child process....
+//     return 0;
+//   }
+
+// Spawns a child process and executes the function |procname| declared using
+// |MULTIPROCESS_TEST_MAIN()| or |MULTIPROCESS_TEST_MAIN_WITH_SETUP()|.
+// |command_line| should be as provided by
+// |GetMultiProcessTestChildBaseCommandLine()| (below), possibly with arguments
+// added. Note: On Windows, you probably want to set |options.start_hidden|.
+ProcessHandle SpawnMultiProcessTestChild(
+    const std::string& procname,
+    const CommandLine& command_line,
+    const LaunchOptions& options,
+    bool debug_on_start);
+
+// Gets the base command line for |SpawnMultiProcessTestChild()|. To this, you
+// may add any flags needed for your child process.
+CommandLine GetMultiProcessTestChildBaseCommandLine();
+
+// MultiProcessTest ------------------------------------------------------------
+
 // A MultiProcessTest is a test class which makes it easier to
 // write a test which requires code running out of process.
 //
@@ -64,6 +117,12 @@ class MultiProcessTest : public PlatformTest {
                                       bool debug_on_start);
 
   // Set up the command line used to spawn the child process.
+  // Override this to add things to the command line (calling this first in the
+  // override).
+  // Note that currently some tests rely on this providing a full command line,
+  // which they then use directly with |LaunchProcess()|.
+  // TODO(viettrungluu): Remove this and add a virtual
+  // |ModifyChildCommandLine()|; make the two divergent uses more sane.
   virtual CommandLine MakeCmdLine(const std::string& procname,
                                   bool debug_on_start);
 

base/test/multiprocess_test_android.cc

@@ -15,14 +15,15 @@ namespace base {
 // A very basic implementation for Android. On Android tests can run in an APK
 // and we don't have an executable to exec*. This implementation does the bare
 // minimum to execute the method specified by procname (in the child process).
+//  - |base_command_line| is ignored.
 //  - All options except |fds_to_remap| are ignored.
 //  - |debug_on_start| is ignored.
-ProcessHandle MultiProcessTest::SpawnChildWithOptions(
-    const std::string& procname,
-    const LaunchOptions& options,
-    bool debug_on_start) {
-  // TODO(vtl): The FD-remapping done below is wrong in the presence of cycles
-  // (e.g., fd1 -> fd2, fd2 -> fd1). crbug.com/326576
+ProcessHandle SpawnMultiProcessTestChild(const std::string& procname,
+                                         const CommandLine& base_command_line,
+                                         const LaunchOptions& options,
+                                         bool debug_on_start) {
+  // TODO(viettrungluu): The FD-remapping done below is wrong in the presence of
+  // cycles (e.g., fd1 -> fd2, fd2 -> fd1). crbug.com/326576
   FileHandleMappingVector empty;
   const FileHandleMappingVector* fds_to_remap =
       options.fds_to_remap ? options.fds_to_remap : ∅