Add SingleLogSource to system_logs sources

chrome/browser/chromeos/system_logs/single_log_source_unittest.cc

+// Copyright 2017 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 "chrome/browser/chromeos/system_logs/single_log_source.h"
+
+#include <string>
+
+#include "base/bind.h"
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/files/scoped_temp_dir.h"
+#include "base/macros.h"
+#include "base/run_loop.h"
+#include "base/test/scoped_task_scheduler.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace system_logs {
+
+class SingleLogSourceTest : public ::testing::Test {
+ public:
+  SingleLogSourceTest()
+      : source_(SingleLogSource::SupportedSource::kMessages),
+        num_callback_calls_(0) {
+    CHECK(dir_.CreateUniqueTempDir());
+    log_file_path_ = dir_.GetPath().Append("log_file");
+
+    // Create the dummy log file for writing.
+    base::File new_file;
+    new_file.Initialize(log_file_path_, base::File::FLAG_CREATE_ALWAYS |
+                                            base::File::FLAG_WRITE);
+    new_file.Close();
+    CHECK(base::PathExists(log_file_path_));
+
+    // Open the dummy log file for reading from within the log source.
+    source_.file_.Initialize(log_file_path_,
+                             base::File::FLAG_OPEN | base::File::FLAG_READ);
+    CHECK(source_.file_.IsValid());
+  }
+
+  ~SingleLogSourceTest() override {}
+
+  // Writes a string to |log_file_path_|.
+  bool WriteFile(const std::string& input) {
+    return base::WriteFile(log_file_path_, input.data(), input.size());
+  }
+  // Appends a string to |log_file_path_|.
+  bool AppendToFile(const std::string& input) {
+    return base::AppendToFile(log_file_path_, input.data(), input.size());
+  }
+
+  // Calls source_.Fetch() to start a logs fetch operation. Passes in
+  // OnFileRead() as a callback. Runs until Fetch() has completed.
+  void FetchFromSource() {
+    source_.Fetch(
+        base::Bind(&SingleLogSourceTest::OnFileRead, base::Unretained(this)));
+    base::RunLoop().RunUntilIdle();
+  }
+
+  // Callback for fetching logs from |source_|. Overwrites the previous stored
+  // value of |latest_response_|.
+  void OnFileRead(SystemLogsResponse* response) {
+    ++num_callback_calls_;
+    if (response->empty())
+      return;
+
+    // Since |source_| represents a single log source, it should only return a
+    // single string result.
+    EXPECT_EQ(1U, response->size());
+    latest_response_ = std::move(response->begin()->second);
+  }
+
+  int num_callback_calls() const { return num_callback_calls_; }
+
+  const std::string& latest_response() const { return latest_response_; }
+
+  const base::FilePath& log_file_path() const { return log_file_path_; }
+
+ private:
+  // Unit under test.
+  SingleLogSource source_;
+
+  // Counts the number of times that |source_| has invoked the callback.
+  int num_callback_calls_;
+
+  // Stores the string response returned from |source_| the last time it invoked
+  // OnFileRead.
+  std::string latest_response_;
+
+  // Temporary dir for creating a dummy log file.
+  base::ScopedTempDir dir_;
+
+  // Path to the dummy log file in |dir_|.
+  base::FilePath log_file_path_;
+
+  // Used for running scheduled tasks.
+  base::test::ScopedTaskScheduler scheduler_;

[afakhry, 2017/05/11 00:56:54]

Can you also add a member of type content::TestBrowserThreadBundle to overcome
those failures?

To validate that it works. Build a debug version of your test, and run it to
make sure you don't encounter those failures.

Always run unit tests in a debug build as DCHECKs are enabled and you'd know if
you made a mistake.

gn gen out/debug --args="is_debug=true .... etc."

+
+  DISALLOW_COPY_AND_ASSIGN(SingleLogSourceTest);
+};
+
+TEST_F(SingleLogSourceTest, EmptyFile) {
+  FetchFromSource();
+
+  EXPECT_EQ(1, num_callback_calls());
+  EXPECT_EQ("", latest_response());
+}
+
+TEST_F(SingleLogSourceTest, SingleRead) {
+  EXPECT_TRUE(AppendToFile("Hello world!\n"));
+  FetchFromSource();
+
+  EXPECT_EQ(1, num_callback_calls());
+  EXPECT_EQ("Hello world!\n", latest_response());
+}
+
+TEST_F(SingleLogSourceTest, IncrementalReads) {
+  EXPECT_TRUE(AppendToFile("Hello world!\n"));
+  FetchFromSource();
+
+  EXPECT_EQ(1, num_callback_calls());
+  EXPECT_EQ("Hello world!\n", latest_response());
+
+  EXPECT_TRUE(AppendToFile("The quick brown fox jumps over the lazy dog\n"));
+  FetchFromSource();
+
+  EXPECT_EQ(2, num_callback_calls());
+  EXPECT_EQ("The quick brown fox jumps over the lazy dog\n", latest_response());
+
+  EXPECT_TRUE(AppendToFile("Some like it hot.\nSome like it cold\n"));
+  FetchFromSource();
+
+  EXPECT_EQ(3, num_callback_calls());
+  EXPECT_EQ("Some like it hot.\nSome like it cold\n", latest_response());
+
+  // As a sanity check, read entire contents of file separately to make sure it
+  // was written incrementally, and hence read incrementally.
+  std::string file_contents;
+  EXPECT_TRUE(base::ReadFileToString(log_file_path(), &file_contents));
+  EXPECT_EQ(
+      "Hello world!\nThe quick brown fox jumps over the lazy dog\n"
+      "Some like it hot.\nSome like it cold\n",
+      file_contents);
+}
+
+// The log files read by SingleLogSource are not expected to be overwritten.
+// This test is just to ensure that the SingleLogSource class is robust enough
+// not to break in the event of an overwrite.
+TEST_F(SingleLogSourceTest, FileOverwrite) {
+  EXPECT_TRUE(AppendToFile("0123456789\n"));
+  FetchFromSource();
+
+  EXPECT_EQ(1, num_callback_calls());
+  EXPECT_EQ("0123456789\n", latest_response());
+
+  // Overwrite the file.
+  EXPECT_TRUE(WriteFile("abcdefg\n"));
+  FetchFromSource();
+
+  // Should re-read from the beginning.
+  EXPECT_EQ(2, num_callback_calls());
+  EXPECT_EQ("abcdefg\n", latest_response());
+
+  // Append to the file to make sure incremental read still works.
+  EXPECT_TRUE(AppendToFile("hijk\n"));
+  FetchFromSource();
+
+  EXPECT_EQ(3, num_callback_calls());
+  EXPECT_EQ("hijk\n", latest_response());
+
+  // Overwrite again, this time with a longer length than the existing file.
+  // Previous contents:
+  //   abcdefg~hijk~     <-- "~" is a single-char representation of newline.
+  // New contents:
+  //   lmnopqrstuvwxyz~  <-- excess text beyond end of prev contents: "yz~"
+  EXPECT_TRUE(WriteFile("lmnopqrstuvwxyz\n"));
+  FetchFromSource();
+
+  EXPECT_EQ(4, num_callback_calls());
+  EXPECT_EQ("yz\n", latest_response());
+}
+
+TEST_F(SingleLogSourceTest, IncompleteLines) {
+  EXPECT_TRUE(AppendToFile("0123456789"));
+  FetchFromSource();
+
+  EXPECT_EQ(1, num_callback_calls());
+  EXPECT_EQ("", latest_response());
+
+  EXPECT_TRUE(AppendToFile("abcdefg"));
+  FetchFromSource();
+
+  EXPECT_EQ(2, num_callback_calls());
+  EXPECT_EQ("", latest_response());
+
+  EXPECT_TRUE(AppendToFile("hijk\n"));
+  FetchFromSource();
+
+  EXPECT_EQ(3, num_callback_calls());
+  // All the previously written text should be read this time.
+  EXPECT_EQ("0123456789abcdefghijk\n", latest_response());
+
+  EXPECT_TRUE(AppendToFile("Hello world\n"));
+  EXPECT_TRUE(AppendToFile("Goodbye world"));
+  FetchFromSource();
+
+  // Partial whole-line reads are not supported. The last byte of the read must
+  // be a new line.
+  EXPECT_EQ(4, num_callback_calls());
+  EXPECT_EQ("", latest_response());
+
+  EXPECT_TRUE(AppendToFile("\n"));
+  FetchFromSource();
+
+  EXPECT_EQ(5, num_callback_calls());
+  EXPECT_EQ("Hello world\nGoodbye world\n", latest_response());
+}
+
+TEST_F(SingleLogSourceTest, Anonymize) {
+  EXPECT_TRUE(AppendToFile("My MAC address is: 11:22:33:44:55:66\n"));
+  FetchFromSource();
+
+  EXPECT_EQ(1, num_callback_calls());
+  EXPECT_EQ("My MAC address is: 11:22:33:00:00:01\n", latest_response());
+
+  // Suppose the write operation is not atomic, and the MAC address is written
+  // across two separate writes.
+  EXPECT_TRUE(AppendToFile("Your MAC address is: AB:88:C"));
+  FetchFromSource();
+
+  EXPECT_EQ(2, num_callback_calls());
+  EXPECT_EQ("", latest_response());
+
+  EXPECT_TRUE(AppendToFile("D:99:EF:77\n"));
+  FetchFromSource();
+
+  EXPECT_EQ(3, num_callback_calls());
+  EXPECT_EQ("Your MAC address is: ab:88:cd:00:00:02\n", latest_response());
+}
+
+}  // namespace system_logs