diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3248a52..061ca8a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -169,8 +169,8 @@ set(META_APP_AUTHOR "Martchus")
 set(META_APP_URL "https://github.com/${META_APP_AUTHOR}/${META_PROJECT_NAME}")
 set(META_APP_DESCRIPTION "C++ library for reading and writing MP4 (iTunes), ID3, Vorbis, Opus, FLAC and Matroska tags")
 set(META_VERSION_MAJOR 6)
-set(META_VERSION_MINOR 3)
-set(META_VERSION_PATCH 1)
+set(META_VERSION_MINOR 4)
+set(META_VERSION_PATCH 0)
 set(META_PUBLIC_SHARED_LIB_DEPENDS c++utilities)
 set(META_PUBLIC_STATIC_LIB_DEPENDS c++utilities_static)
 set(META_PRIVATE_COMPILE_DEFINITIONS LEGACY_API)
diff --git a/abstracttrack.h b/abstracttrack.h
index 24054f0..8e6647d 100644
--- a/abstracttrack.h
+++ b/abstracttrack.h
@@ -66,12 +66,14 @@ public:
     uint64 id() const;
     void setId(uint64 id);
     const std::string name() const;
+    void setName(const std::string &name);
     const ChronoUtilities::TimeSpan &duration() const;
     double bitrate() const;
     double maxBitrate() const;
     const ChronoUtilities::DateTime &creationTime() const;
     const ChronoUtilities::DateTime &modificationTime() const;
     const std::string &language() const;
+    void setLanguage(const std::string &language);
     uint32 samplingFrequency() const;
     uint32 extensionSamplingFrequency() const;
     uint16 bitsPerSample() const;
@@ -86,6 +88,7 @@ public:
     const Size &displaySize() const;
     const Size &resolution() const;
     const std::string &compressorName() const;
+    void setCompressorName(const std::string &compressorName);
     uint16 depth() const;
     uint32 fps() const;
     const char *chromaFormat() const;
@@ -93,8 +96,11 @@ public:
     bool isInterlaced() const;
     uint32 timeScale() const;
     bool isEnabled() const;
+    void setEnabled(bool enabled);
     bool isDefault() const;
+    void setDefault(bool isDefault);
     bool isForced() const;
+    void setForced(bool forced);
     bool hasLacing() const;
     bool isEncrypted() const;
     uint32 colorSpace() const;
@@ -341,6 +347,15 @@ inline const std::string AbstractTrack::name() const
     return m_name;
 }
 
+/*!
+ * \brief Sets the name.
+ * \remarks Whether the new value is applied when saving changes depends on the implementation.
+ */
+inline void AbstractTrack::setName(const std::string &name)
+{
+    m_name = name;
+}
+
 /*!
  * \brief Returns the duration if known; otherwise returns a TimeSpan of zero ticks.
  */
@@ -391,6 +406,15 @@ inline const std::string &AbstractTrack::language() const
     return m_language;
 }
 
+/*!
+ * \brief Sets the language of the track.
+ * \remarks Whether the new value is applied when saving changes depends on the implementation.
+ */
+inline void AbstractTrack::setLanguage(const std::string &language)
+{
+    m_language = language;
+}
+
 /*!
  * \brief Returns the number of samples per second if known; otherwise returns 0.
  */
@@ -493,6 +517,15 @@ inline const std::string &AbstractTrack::compressorName() const
     return m_compressorName;
 }
 
+/*!
+ * \brief Returns the compressor name if known; otherwise returns an empty string.
+ * \remarks Whether the new value is applied when saving changes depends on the implementation.
+ */
+inline void AbstractTrack::setCompressorName(const std::string &compressorName)
+{
+    m_compressorName = compressorName;
+}
+
 /*!
  * \brief Returns the bit depth if known; otherwise returns 0.
  */
@@ -557,6 +590,15 @@ inline bool AbstractTrack::isEnabled() const
     return m_enabled;
 }
 
+/*!
+ * \brief Sets whether the track is enabled.
+ * \remarks Whether the new value is applied when saving changes depends on the implementation.
+ */
+inline void AbstractTrack::setEnabled(bool enabled)
+{
+    m_enabled = enabled;
+}
+
 /*!
  * \brief Returns true if the track is denoted as default; otherwise returns false.
  */
@@ -565,6 +607,15 @@ inline bool AbstractTrack::isDefault() const
     return m_default;
 }
 
+/*!
+ * \brief Sets whether the track is a default track.
+ * \remarks Whether the new value is applied when saving changes depends on the implementation.
+ */
+inline void AbstractTrack::setDefault(bool isDefault)
+{
+    m_default = isDefault;
+}
+
 /*!
  * \brief Returns true if the track is denoted as forced; otherwise returns false.
  */
@@ -573,6 +624,15 @@ inline bool AbstractTrack::isForced() const
     return m_forced;
 }
 
+/*!
+ * \brief Sets whether the track is forced.
+ * \remarks Whether the new value is applied when saving changes depends on the implementation.
+ */
+inline void AbstractTrack::setForced(bool forced)
+{
+    m_forced = forced;
+}
+
 /*!
  * \brief Returns true if the track has lacing; otherwise returns false.
  */
diff --git a/tests/overall.h b/tests/overall.h
index d986f86..692799b 100644
--- a/tests/overall.h
+++ b/tests/overall.h
@@ -106,7 +106,7 @@ private:
     void removeAllTags();
     void noop();
     void createMkvWithNestedTags();
-    void addMp4Track();
+    void alterMp4Tracks();
     void removeSecondTrack();
 
 public:
diff --git a/tests/overallflac.cpp b/tests/overallflac.cpp
index 458ba9f..4265f71 100644
--- a/tests/overallflac.cpp
+++ b/tests/overallflac.cpp
@@ -41,7 +41,7 @@ void OverallTests::checkFlacTestfile1()
         checkOggTestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -71,7 +71,7 @@ void OverallTests::checkFlacTestfile2()
         checkOggTestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
diff --git a/tests/overallmkv.cpp b/tests/overallmkv.cpp
index 35be04d..d03775d 100644
--- a/tests/overallmkv.cpp
+++ b/tests/overallmkv.cpp
@@ -62,7 +62,7 @@ void OverallTests::checkMkvTestfile1()
         checkMkvTestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -102,7 +102,7 @@ void OverallTests::checkMkvTestfile2()
         checkMkvTestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -142,7 +142,7 @@ void OverallTests::checkMkvTestfile3()
         checkMkvTestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -176,7 +176,7 @@ void OverallTests::checkMkvTestfile4()
     switch(m_tagStatus) {
     case TagStatus::Original:
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
         break;
     case TagStatus::TestMetaDataPresent:
         checkMkvTestMetaData();
@@ -226,7 +226,7 @@ void OverallTests::checkMkvTestfile5()
         checkMkvTestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -267,7 +267,7 @@ void OverallTests::checkMkvTestfile6()
         checkMkvTestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -309,7 +309,7 @@ void OverallTests::checkMkvTestfile7()
         checkMkvTestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -351,7 +351,7 @@ void OverallTests::checkMkvTestfile8()
         checkMkvTestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -415,7 +415,7 @@ void OverallTests::checkMkvTestfileHandbrakeChapters()
         checkMkvTestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -451,7 +451,7 @@ void OverallTests::checkMkvTestfileNestedTags()
         CPPUNIT_ASSERT(generalTagFound);
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tags.size());
     }
 }
 
diff --git a/tests/overallmp3.cpp b/tests/overallmp3.cpp
index 54567ae..8f94aec 100644
--- a/tests/overallmp3.cpp
+++ b/tests/overallmp3.cpp
@@ -77,7 +77,7 @@ void OverallTests::checkMp3Testfile1()
         checkMp3TestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 
 }
diff --git a/tests/overallmp4.cpp b/tests/overallmp4.cpp
index a783b74..94489e4 100644
--- a/tests/overallmp4.cpp
+++ b/tests/overallmp4.cpp
@@ -53,7 +53,7 @@ void OverallTests::checkMp4Testfile1()
         checkMp4TestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -68,11 +68,11 @@ void OverallTests::checkMp4Testfile2()
     for(const auto &track : tracks) {
         switch(track->id()) {
         case 1:
-            CPPUNIT_ASSERT(track->mediaType() == MediaType::Video);
-            CPPUNIT_ASSERT(track->format() == GeneralMediaFormat::Avc);
-            CPPUNIT_ASSERT(track->format().sub == SubFormats::AvcHighProfile);
+            CPPUNIT_ASSERT_EQUAL(MediaType::Video, track->mediaType());
+            CPPUNIT_ASSERT_EQUAL(GeneralMediaFormat::Avc, track->format().general);
+            CPPUNIT_ASSERT_EQUAL(static_cast<unsigned char>(SubFormats::AvcHighProfile), track->format().sub);
             CPPUNIT_ASSERT_EQUAL(4.0, track->version());
-            CPPUNIT_ASSERT(track->creationTime().year() == 2013);
+            CPPUNIT_ASSERT_EQUAL(2013, track->creationTime().year());
             CPPUNIT_ASSERT(track->pixelSize() == Size(1920, 750));
             break;
         case 2:
@@ -87,21 +87,21 @@ void OverallTests::checkMp4Testfile2()
             CPPUNIT_ASSERT_EQUAL(static_cast<unsigned char>(Mpeg4ChannelConfigs::FrontLeftFrontRight), track->channelConfig());
             break;
         case 3:
-            CPPUNIT_ASSERT(track->mediaType() == MediaType::Audio);
-            CPPUNIT_ASSERT(track->format() == GeneralMediaFormat::Ac3);
+            CPPUNIT_ASSERT_EQUAL(MediaType::Audio, track->mediaType());
+            CPPUNIT_ASSERT_EQUAL(GeneralMediaFormat::Ac3, track->format().general);
             CPPUNIT_ASSERT_EQUAL("eng"s, track->language());
-            CPPUNIT_ASSERT(track->creationTime().year() == 2013);
+            CPPUNIT_ASSERT_EQUAL(2013, track->creationTime().year());
             break;
         case 4:
-            CPPUNIT_ASSERT(track->mediaType() == MediaType::Audio);
-            CPPUNIT_ASSERT(track->format() == GeneralMediaFormat::DtsHd);
+            CPPUNIT_ASSERT_EQUAL(MediaType::Audio, track->mediaType());
+            CPPUNIT_ASSERT_EQUAL(GeneralMediaFormat::DtsHd, track->format().general);
             CPPUNIT_ASSERT_EQUAL("eng"s, track->language());
-            CPPUNIT_ASSERT(track->creationTime().year() == 2013);
+            CPPUNIT_ASSERT_EQUAL(2013, track->creationTime().year());
             break;
         case 6:
-            CPPUNIT_ASSERT(track->mediaType() == MediaType::Text);
-            CPPUNIT_ASSERT(track->format() == GeneralMediaFormat::TimedText);
-            CPPUNIT_ASSERT(track->creationTime().year() == 2013);
+            CPPUNIT_ASSERT_EQUAL(MediaType::Text, track->mediaType());
+            CPPUNIT_ASSERT_EQUAL(GeneralMediaFormat::TimedText, track->format().general);
+            CPPUNIT_ASSERT_EQUAL(2013, track->creationTime().year());
             break;
         default:
             CPPUNIT_FAIL("unknown track ID");
@@ -147,13 +147,13 @@ void OverallTests::checkMp4Testfile3()
     const auto tags = m_fileInfo.tags();
     switch(m_tagStatus) {
     case TagStatus::Original:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
         break;
     case TagStatus::TestMetaDataPresent:
         checkMp4TestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -169,8 +169,8 @@ void OverallTests::checkMp4Testfile4()
     for(const auto &track : tracks) {
         switch(track->id()) {
         case 1:
-            CPPUNIT_ASSERT(track->mediaType() == MediaType::Audio);
-            CPPUNIT_ASSERT(track->format() == GeneralMediaFormat::Alac);
+            CPPUNIT_ASSERT_EQUAL(MediaType::Audio, track->mediaType());
+            CPPUNIT_ASSERT_EQUAL(GeneralMediaFormat::Alac, track->format().general);
             CPPUNIT_ASSERT(track->creationTime().year() == 2008);
             CPPUNIT_ASSERT(track->channelCount() == 2);
             CPPUNIT_ASSERT(track->bitsPerSample() == 16);
@@ -199,7 +199,7 @@ void OverallTests::checkMp4Testfile4()
         checkMp4TestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -215,9 +215,9 @@ void OverallTests::checkMp4Testfile5()
     for(const auto &track : tracks) {
         switch(track->id()) {
         case 1:
-            CPPUNIT_ASSERT(track->mediaType() == MediaType::Audio);
-            CPPUNIT_ASSERT(track->format() == GeneralMediaFormat::Aac);
-            CPPUNIT_ASSERT(track->format().sub == SubFormats::AacMpeg4LowComplexityProfile);
+            CPPUNIT_ASSERT_EQUAL(MediaType::Audio, track->mediaType());
+            CPPUNIT_ASSERT_EQUAL(GeneralMediaFormat::Aac, track->format().general);
+            CPPUNIT_ASSERT_EQUAL(static_cast<unsigned char>(SubFormats::AacMpeg4LowComplexityProfile), track->format().sub);
             CPPUNIT_ASSERT(track->format().extension & ExtensionFormats::SpectralBandReplication);
             CPPUNIT_ASSERT(track->format().extension & ExtensionFormats::ParametricStereo);
             CPPUNIT_ASSERT(track->creationTime().year() == 2014);
@@ -235,13 +235,13 @@ void OverallTests::checkMp4Testfile5()
     const auto tags = m_fileInfo.tags();
     switch(m_tagStatus) {
     case TagStatus::Original:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
         break;
     case TagStatus::TestMetaDataPresent:
         checkMp4TestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -253,19 +253,19 @@ void OverallTests::checkMp4Testfile6()
     CPPUNIT_ASSERT(m_fileInfo.containerFormat() == ContainerFormat::Mp4);
     const auto tracks = m_fileInfo.tracks();
     if(m_mode & Mp4TestFlags::RemoveTagOrTrack) {
-        CPPUNIT_ASSERT(tracks.size() == 4);
+        CPPUNIT_ASSERT_EQUAL(4_st, tracks.size());
     } else {
-        CPPUNIT_ASSERT(tracks.size() == 6);
+        CPPUNIT_ASSERT_EQUAL(6_st, tracks.size());
     }
     bool track2Present = false, track5Present = false;
     for(const auto &track : tracks) {
         switch(track->id()) {
         case 1:
-            CPPUNIT_ASSERT(track->mediaType() == MediaType::Video);
-            CPPUNIT_ASSERT(track->format() == GeneralMediaFormat::Avc);
-            CPPUNIT_ASSERT(track->format().sub == SubFormats::AvcHighProfile);
-            CPPUNIT_ASSERT(track->version() == 4);
-            CPPUNIT_ASSERT(track->creationTime().year() == 2013);
+            CPPUNIT_ASSERT_EQUAL(MediaType::Video, track->mediaType());
+            CPPUNIT_ASSERT_EQUAL(GeneralMediaFormat::Avc, track->format().general);
+            CPPUNIT_ASSERT_EQUAL(static_cast<unsigned char>(SubFormats::AvcHighProfile), track->format().sub);
+            CPPUNIT_ASSERT_EQUAL(4.0, track->version());
+            CPPUNIT_ASSERT_EQUAL(2013, track->creationTime().year());
             CPPUNIT_ASSERT(track->pixelSize() == Size(1920, 750));
             break;
         case 2:
@@ -275,22 +275,23 @@ void OverallTests::checkMp4Testfile6()
             CPPUNIT_ASSERT_EQUAL(static_cast<unsigned char>(SubFormats::AacMpeg4LowComplexityProfile), track->format().sub);
             CPPUNIT_ASSERT(!(track->format().extension & ExtensionFormats::SpectralBandReplication));
             CPPUNIT_ASSERT(!(track->format().extension & ExtensionFormats::ParametricStereo));
-            CPPUNIT_ASSERT_EQUAL("eng"s, track->language());
+            CPPUNIT_ASSERT_EQUAL("ger"s, track->language());
+            CPPUNIT_ASSERT_EQUAL("test"s, track->name());
             CPPUNIT_ASSERT_EQUAL(2013, track->creationTime().year());
             CPPUNIT_ASSERT_EQUAL(48000u, track->samplingFrequency());
             CPPUNIT_ASSERT_EQUAL(static_cast<unsigned char>(Mpeg4ChannelConfigs::FrontLeftFrontRight), track->channelConfig());
             break;
         case 3:
-            CPPUNIT_ASSERT(track->mediaType() == MediaType::Audio);
-            CPPUNIT_ASSERT(track->format() == GeneralMediaFormat::Ac3);
-            CPPUNIT_ASSERT(track->language() == "eng");
-            CPPUNIT_ASSERT(track->creationTime().year() == 2013);
+            CPPUNIT_ASSERT_EQUAL(MediaType::Audio, track->mediaType());
+            CPPUNIT_ASSERT_EQUAL(GeneralMediaFormat::Ac3, track->format().general);
+            CPPUNIT_ASSERT_EQUAL("eng"s, track->language());
+            CPPUNIT_ASSERT_EQUAL(2013, track->creationTime().year());
             break;
         case 4:
-            CPPUNIT_ASSERT(track->mediaType() == MediaType::Audio);
-            CPPUNIT_ASSERT(track->format() == GeneralMediaFormat::DtsHd);
-            CPPUNIT_ASSERT(track->language() == "eng");
-            CPPUNIT_ASSERT(track->creationTime().year() == 2013);
+            CPPUNIT_ASSERT_EQUAL(MediaType::Audio, track->mediaType());
+            CPPUNIT_ASSERT_EQUAL(GeneralMediaFormat::DtsHd, track->format().general);
+            CPPUNIT_ASSERT_EQUAL("eng"s, track->language());
+            CPPUNIT_ASSERT_EQUAL(2013, track->creationTime().year());
             break;
         case 5:
             CPPUNIT_ASSERT(track5Present = !track5Present);
@@ -299,11 +300,12 @@ void OverallTests::checkMp4Testfile6()
             CPPUNIT_ASSERT_EQUAL(2012, track->creationTime().year());
             CPPUNIT_ASSERT_EQUAL(44100u, track->samplingFrequency());
             CPPUNIT_ASSERT_EQUAL(static_cast<byte>(Mpeg4ChannelConfigs::FrontLeftFrontRight), track->channelConfig());
+            CPPUNIT_ASSERT_EQUAL("new track"s, track->name());
             break;
         case 6:
-            CPPUNIT_ASSERT(track->mediaType() == MediaType::Text);
-            CPPUNIT_ASSERT(track->format() == GeneralMediaFormat::TimedText);
-            CPPUNIT_ASSERT(track->creationTime().year() == 2013);
+            CPPUNIT_ASSERT_EQUAL(MediaType::Text, track->mediaType());
+            CPPUNIT_ASSERT_EQUAL(GeneralMediaFormat::TimedText, track->format().general);
+            CPPUNIT_ASSERT_EQUAL(2013, track->creationTime().year());
             break;
         default:
             CPPUNIT_FAIL("unknown track ID");
@@ -317,7 +319,7 @@ void OverallTests::checkMp4Testfile6()
         CPPUNIT_ASSERT(track5Present);
     }
 
-    CPPUNIT_ASSERT(m_fileInfo.tags().size() == 0);
+    CPPUNIT_ASSERT_EQUAL(0_st, m_fileInfo.tags().size());
 }
 
 /*!
@@ -386,9 +388,13 @@ void OverallTests::setMp4TestMetaData()
 }
 
 /*!
- * \brief Adds all tracks from mtx-test-data/mp4/10-DanseMacabreOp.40.m4a to the file to be tested.
+ * \brief Alters the tracks of the file to be testd.
+ *
+ * - Adds track from mtx-test-data/mp4/10-DanseMacabreOp.40.m4a
+ * - Sets the language of the 2nd track to German
+ * - Sets the name of the 2nd track to "test".
  */
-void OverallTests::addMp4Track()
+void OverallTests::alterMp4Tracks()
 {
     m_additionalFileInfo.setPath(TestUtilities::testFilePath("mtx-test-data/mp4/10-DanseMacabreOp.40.m4a"));
     m_additionalFileInfo.reopen(true);
@@ -401,7 +407,15 @@ void OverallTests::addMp4Track()
     CPPUNIT_ASSERT_EQUAL(TrackType::Mp4Track, tracks[0]->type());
     auto *track = static_cast<Mp4Track *>(tracks[0]);
     CPPUNIT_ASSERT(static_cast<Mp4Container *>(m_additionalFileInfo.container())->removeTrack(track));
-    static_cast<Mp4Container *>(m_fileInfo.container())->addTrack(track);
+    CPPUNIT_ASSERT_EQUAL(0_st, m_additionalFileInfo.trackCount());
+    track->setName("new track");
+    auto *container = static_cast<Mp4Container *>(m_fileInfo.container());
+    CPPUNIT_ASSERT_EQUAL(5_st, container->trackCount());
+    container->addTrack(track);
+    CPPUNIT_ASSERT_EQUAL(6_st, container->trackCount());
+    auto &secondTrack = container->tracks()[1];
+    secondTrack->setLanguage("ger");
+    secondTrack->setName("test");
 }
 
 /*!
@@ -482,7 +496,7 @@ void OverallTests::testMp4Making()
         makeFile(TestUtilities::workingCopyPath("mtx-test-data/alac/othertest-itunes.m4a"), modifyRoutine, &OverallTests::checkMp4Testfile4);
         makeFile(TestUtilities::workingCopyPath("mtx-test-data/aac/he-aacv2-ps.m4a"), modifyRoutine, &OverallTests::checkMp4Testfile5);
         // -> add/remove tracks
-        modifyRoutine = (m_mode & RemoveTagOrTrack) ? &OverallTests::removeSecondTrack : &OverallTests::addMp4Track;
+        modifyRoutine = (m_mode & RemoveTagOrTrack) ? &OverallTests::removeSecondTrack : &OverallTests::alterMp4Tracks;
         m_fileInfo.setTagPosition(ElementPosition::Keep);
         makeFile(TestUtilities::workingCopyPath("mtx-test-data/mp4/1080p-DTS-HD-7.1.mp4"), modifyRoutine, &OverallTests::checkMp4Testfile6);
     }
diff --git a/tests/overallogg.cpp b/tests/overallogg.cpp
index c804202..3df7f2d 100644
--- a/tests/overallogg.cpp
+++ b/tests/overallogg.cpp
@@ -42,7 +42,7 @@ void OverallTests::checkOggTestfile1()
         checkOggTestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }
 
@@ -77,7 +77,7 @@ void OverallTests::checkOggTestfile2()
         checkOggTestMetaData();
         break;
     case TagStatus::Removed:
-        CPPUNIT_ASSERT(tags.size() == 0);
+        CPPUNIT_ASSERT_EQUAL(0_st, tracks.size());
     }
 }