Fix VideoFileWriterTest flakiness by using unique file path.

Both reference and tested videos were created
via a file whose path was fixed.
So, when tests were launched in parallel, race conditions ensued.
This CL creates an unique temporary filename for each video.

Bug: webrtc:10156
Change-Id: Ie3abf85abdfa95735cb86880bbd6a59393e609c1
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/127883
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Paulina Hensman <phensman@webrtc.org>
Commit-Queue: Yves Gerey <yvesg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27219}
diff --git a/rtc_tools/video_file_writer_unittest.cc b/rtc_tools/video_file_writer_unittest.cc
index 9a74b5f..fea01ba 100644
--- a/rtc_tools/video_file_writer_unittest.cc
+++ b/rtc_tools/video_file_writer_unittest.cc
@@ -24,11 +24,11 @@
 class VideoFileWriterTest : public ::testing::Test {
  public:
   void SetUp() override {
-    const std::string filename =
-        webrtc::test::OutputPath() + "test_video_file.y4m";
+    video_filename_ =
+        TempFilename(webrtc::test::OutputPath(), "test_video_file.y4m");
 
     // Create simple test video of size 6x4.
-    FILE* file = fopen(filename.c_str(), "wb");
+    FILE* file = fopen(video_filename_.c_str(), "wb");
     ASSERT_TRUE(file != nullptr);
     fprintf(file, "YUV4MPEG2 W6 H4 F60:1 C420 dummyParam\n");
     fprintf(file, "FRAME\n");
@@ -44,61 +44,85 @@
     fclose(file);
 
     // Open the newly created file.
-    video = webrtc::test::OpenY4mFile(filename);
-    ASSERT_TRUE(video);
+    video_ = webrtc::test::OpenY4mFile(video_filename_);
+    ASSERT_TRUE(video_);
+    ASSERT_EQ(video_->number_of_frames(), 2u);
+  }
+
+  void TearDown() override {
+    if (!video_filename_.empty()) {
+      RemoveFile(video_filename_);
+    }
+    if (!written_video_filename_.empty()) {
+      RemoveFile(written_video_filename_);
+    }
   }
 
   // Write and read Y4M file.
   void WriteVideoY4m() {
-    const std::string filename =
-        webrtc::test::OutputPath() + "test_video_file2.y4m";
-    webrtc::test::WriteVideoToFile(video, filename, fps);
-    written_video = webrtc::test::OpenY4mFile(filename);
-    ASSERT_TRUE(written_video);
+    // Cleanup existing file if any.
+    if (!written_video_filename_.empty()) {
+      RemoveFile(written_video_filename_);
+    }
+    // Create an unique filename, e.g. test_video_file2.y4mZapata.
+    written_video_filename_ =
+        TempFilename(webrtc::test::OutputPath(), "test_video_file2.y4m");
+    webrtc::test::WriteY4mVideoToFile(video_, written_video_filename_, fps);
+    written_video_ = webrtc::test::OpenY4mFile(written_video_filename_);
+    ASSERT_TRUE(written_video_);
   }
 
   // Write and read YUV file.
   void WriteVideoYuv() {
-    const std::string filename =
-        webrtc::test::OutputPath() + "test_video_file2.yuv";
-    webrtc::test::WriteVideoToFile(video, filename, fps);
-    written_video = webrtc::test::OpenYuvFile(filename, width, height);
-    ASSERT_TRUE(written_video);
+    // Cleanup existing file if any.
+    if (!written_video_filename_.empty()) {
+      RemoveFile(written_video_filename_);
+    }
+    // Create an unique filename, e.g. test_video_file2.yuvZapata.
+    written_video_filename_ =
+        TempFilename(webrtc::test::OutputPath(), "test_video_file2.yuv");
+    webrtc::test::WriteYuvVideoToFile(video_, written_video_filename_, fps);
+    written_video_ =
+        webrtc::test::OpenYuvFile(written_video_filename_, width, height);
+    ASSERT_TRUE(written_video_);
   }
 
   const int width = 6;
   const int height = 4;
   const int fps = 60;
-  rtc::scoped_refptr<webrtc::test::Video> video;
-  rtc::scoped_refptr<webrtc::test::Video> written_video;
+  rtc::scoped_refptr<webrtc::test::Video> video_;
+  rtc::scoped_refptr<webrtc::test::Video> written_video_;
+  // Each video object must be backed by file!
+  std::string video_filename_;
+  std::string written_video_filename_;
 };
 
 TEST_F(VideoFileWriterTest, TestParsingFileHeaderY4m) {
   WriteVideoY4m();
-  EXPECT_EQ(video->width(), written_video->width());
-  EXPECT_EQ(video->height(), written_video->height());
+  EXPECT_EQ(video_->width(), written_video_->width());
+  EXPECT_EQ(video_->height(), written_video_->height());
 }
 
 TEST_F(VideoFileWriterTest, TestParsingFileHeaderYuv) {
   WriteVideoYuv();
-  EXPECT_EQ(video->width(), written_video->width());
-  EXPECT_EQ(video->height(), written_video->height());
+  EXPECT_EQ(video_->width(), written_video_->width());
+  EXPECT_EQ(video_->height(), written_video_->height());
 }
 
 TEST_F(VideoFileWriterTest, TestParsingNumberOfFramesY4m) {
   WriteVideoY4m();
-  EXPECT_EQ(video->number_of_frames(), written_video->number_of_frames());
+  EXPECT_EQ(video_->number_of_frames(), written_video_->number_of_frames());
 }
 
 TEST_F(VideoFileWriterTest, TestParsingNumberOfFramesYuv) {
   WriteVideoYuv();
-  EXPECT_EQ(video->number_of_frames(), written_video->number_of_frames());
+  EXPECT_EQ(video_->number_of_frames(), written_video_->number_of_frames());
 }
 
 TEST_F(VideoFileWriterTest, TestPixelContentY4m) {
   WriteVideoY4m();
   int cnt = 0;
-  for (const rtc::scoped_refptr<I420BufferInterface> frame : *written_video) {
+  for (const rtc::scoped_refptr<I420BufferInterface> frame : *written_video_) {
     for (int i = 0; i < width * height; ++i, ++cnt)
       EXPECT_EQ(cnt, frame->DataY()[i]);
     for (int i = 0; i < width / 2 * height / 2; ++i, ++cnt)
@@ -111,7 +135,7 @@
 TEST_F(VideoFileWriterTest, TestPixelContentYuv) {
   WriteVideoYuv();
   int cnt = 0;
-  for (const rtc::scoped_refptr<I420BufferInterface> frame : *written_video) {
+  for (const rtc::scoped_refptr<I420BufferInterface> frame : *written_video_) {
     for (int i = 0; i < width * height; ++i, ++cnt)
       EXPECT_EQ(cnt, frame->DataY()[i]);
     for (int i = 0; i < width / 2 * height / 2; ++i, ++cnt)