gn: beginnings of format command

tools/gn/command_format_unittest.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/files/file_util.h"
+#include "base/strings/string_util.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "tools/gn/commands.h"
+
+namespace commands {
+bool FormatFileToString(const std::string& input_filename, std::string* output);
+}  // namespace commands
+
+TEST(Format, AllTests) {
+  std::string out;
+  std::string expected;
+  for (int i = 1; i <= 3; ++i) {
+    char buf[256];
+    base::snprintf(buf, sizeof(buf), "//tools/gn/format_test_data/%03d.gn", i);
+    EXPECT_TRUE(commands::FormatFileToString(buf, &out));
+    base::FilePath golden;
+    base::snprintf(
+        buf, sizeof(buf), "tools/gn/format_test_data/%03d.golden", i);
+    golden = golden.AppendASCII(buf);
+    ASSERT_TRUE(base::ReadFileToString(golden, &expected));
+    EXPECT_EQ(out, expected);
+  }
+}