[WIP] Monkeypatch tests (#448)

* Parameterize test_internals.py

* Create test_spotify_tools.py

* Monkeypatch pafy.download

* Monkeypatch YouTube search page

* Replace globals with fixtures

* Add missing urllib import, re-ordering and rename test_with_metadata.py

* Avoid creating temp directory in current working directory during test

* Update CHANGES.md

test/test_spotify_tools.py

@@ -0,0 +1,137 @@
+from spotdl import spotify_tools
+
+import os
+import pytest
+
+
+def test_generate_token():
+    token = spotify_tools.generate_token()
+    assert len(token) == 83
+
+
+def test_refresh_token():
+    old_instance = spotify_tools.spotify
+    spotify_tools.refresh_token()
+    new_instance = spotify_tools.spotify
+    assert not old_instance == new_instance
+
+
+class TestGenerateMetadata:
+    @pytest.fixture(scope="module")
+    def metadata_fixture(self):
+        metadata = spotify_tools.generate_metadata("ncs - spectre")
+        return metadata
+
+    def test_len(self, metadata_fixture):
+        assert len(metadata_fixture) == 23
+
+    def test_trackname(self, metadata_fixture):
+        assert metadata_fixture["name"] == "Spectre"
+
+    def test_artist(self, metadata_fixture):
+        assert metadata_fixture["artists"][0]["name"] == "Alan Walker"
+
+    def test_duration(self, metadata_fixture):
+        assert metadata_fixture["duration"] == 230.634
+
+
+def test_get_playlists():
+    expect_playlist_ids = [ "34gWCK8gVeYDPKcctB6BQJ",
+                            "04wTU2c2WNQG9XE5oSLYfj",
+                            "0fWBMhGh38y0wsYWwmM9Kt" ]
+
+    expect_playlists = [ "https://open.spotify.com/playlist/" +  playlist_id
+                         for playlist_id in expect_playlist_ids ]
+
+    playlists = spotify_tools.get_playlists("uqlakumu7wslkoen46s5bulq0")
+    assert playlists == expect_playlists
+
+
+def test_write_user_playlist(tmpdir, monkeypatch):
+    expect_tracks = 17
+    text_file = os.path.join(str(tmpdir), "test_us.txt")
+    monkeypatch.setattr("builtins.input", lambda x: 1)
+    spotify_tools.write_user_playlist("uqlakumu7wslkoen46s5bulq0", text_file)
+    with open(text_file, "r") as f:
+        tracks = len(f.readlines())
+    assert tracks == expect_tracks
+
+
+class TestFetchPlaylist:
+    @pytest.fixture(scope="module")
+    def playlist_fixture(self):
+        playlist = spotify_tools.fetch_playlist("https://open.spotify.com/playlist/0fWBMhGh38y0wsYWwmM9Kt")
+        return playlist
+
+    def test_name(self, playlist_fixture):
+        assert playlist_fixture["name"] == "special_test_playlist"
+
+    def test_tracks(self, playlist_fixture):
+        assert playlist_fixture["tracks"]["total"] == 14
+
+
+def test_write_playlist(tmpdir):
+    expect_tracks = 14
+    text_file = os.path.join(str(tmpdir), "test_pl.txt")
+    spotify_tools.write_playlist("https://open.spotify.com/playlist/0fWBMhGh38y0wsYWwmM9Kt", text_file)
+    with open(text_file, "r") as f:
+        tracks = len(f.readlines())
+    assert tracks == expect_tracks
+
+
+# XXX: Mock this test off if it fails in future
+class TestFetchAlbum:
+    @pytest.fixture(scope="module")
+    def album_fixture(self):
+        album = spotify_tools.fetch_album("https://open.spotify.com/album/499J8bIsEnU7DSrosFDJJg")
+        return album
+
+    def test_name(self, album_fixture):
+        assert album_fixture["name"] == "NCS: Infinity"
+
+    def test_tracks(self, album_fixture):
+        assert album_fixture["tracks"]["total"] == 15
+
+
+# XXX: Mock this test off if it fails in future
+class TestFetchAlbumsFromArtist:
+    @pytest.fixture(scope="module")
+    def albums_from_artist_fixture(self):
+        albums = spotify_tools.fetch_albums_from_artist("https://open.spotify.com/artist/7oPftvlwr6VrsViSDV7fJY")
+        return albums
+
+    def test_len(self, albums_from_artist_fixture):
+        assert len(albums_from_artist_fixture) == 18
+
+    def test_zeroth_album_name(self, albums_from_artist_fixture):
+        assert albums_from_artist_fixture[0]["name"] == "Revolution Radio"
+
+    def test_zeroth_album_tracks(self, albums_from_artist_fixture):
+        assert albums_from_artist_fixture[0]["total_tracks"] == 12
+
+    def test_fist_album_name(self, albums_from_artist_fixture):
+        assert albums_from_artist_fixture[1]["name"] == "Demolicious"
+
+    def test_first_album_tracks(self, albums_from_artist_fixture):
+        assert albums_from_artist_fixture[0]["total_tracks"] == 12
+
+
+# XXX: Mock this test off if it fails in future
+def test_write_all_albums_from_artist(tmpdir):
+    # current number of tracks on spotify since as of 10/10/2018
+    # in US market only
+    expect_tracks = 49
+    text_file = os.path.join(str(tmpdir), "test_ab.txt")
+    spotify_tools.write_all_albums_from_artist("https://open.spotify.com/artist/4dpARuHxo51G3z768sgnrY", text_file)
+    with open(text_file, "r") as f:
+        tracks = len(f.readlines())
+    assert tracks == expect_tracks
+
+
+def test_write_album(tmpdir):
+    expect_tracks = 15
+    text_file = os.path.join(str(tmpdir), "test_al.txt")
+    spotify_tools.write_album("https://open.spotify.com/album/499J8bIsEnU7DSrosFDJJg", text_file)
+    with open(text_file, "r") as f:
+        tracks = len(f.readlines())
+    assert tracks == expect_tracks