Add missing test file

test/AlbumTrackTests.cpp

+#include "Tests.h"
+
+#include "IAlbum.h"
+#include "IAlbumTrack.h"
+#include "IArtist.h"
+
+class AlbumTracks : public Tests
+{
+};
+
+TEST_F( AlbumTracks, Artists )
+{
+    auto album = ml->createAlbum( "album" );
+    auto artist1 = ml->createArtist( "artist 1" );
+    auto artist2 = ml->createArtist( "artist 2" );
+    album->addTrack( "track 1", 1 );
+    album->addTrack( "track 2", 2 );
+    album->addTrack( "track 3", 3 );
+
+    ASSERT_NE( artist1, nullptr );
+    ASSERT_NE( artist2, nullptr );
+
+    auto tracks = album->tracks();
+    for ( auto& t : tracks )
+    {
+        t->addArtist( artist1 );
+        t->addArtist( artist2 );
+
+        auto artists = t->artists();
+        ASSERT_EQ( artists.size(), 2u );
+    }
+
+    auto artists = ml->artists();
+    for ( auto& a : artists )
+    {
+        auto tracks = a->tracks();
+        ASSERT_EQ( tracks.size(), 3u );
+    }
+
+    Reload();
+
+    album = ml->album( "album" );
+    tracks = album->tracks();
+    for ( auto& t : tracks )
+    {
+        auto artists = t->artists();
+        ASSERT_EQ( artists.size(), 2u );
+    }
+
+    artists = ml->artists();
+    for ( auto& a : artists )
+    {
+        auto tracks = a->tracks();
+        ASSERT_EQ( tracks.size(), 3u );
+    }
+}