diff --git a/rose/artiststr/__init__.py b/rose/artiststr/__init__.py
index 108c453..75a93b8 100644
--- a/rose/artiststr/__init__.py
+++ b/rose/artiststr/__init__.py
@@ -1,17 +1,17 @@
 import re
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 
 TAG_SPLITTER_REGEX = re.compile(r" \\\\ | / |; ?| vs\. ")
 
 
 @dataclass
 class Artists:
-    main: list[str]
-    guest: list[str]
-    remixer: list[str]
-    producer: list[str]
-    composer: list[str]
-    djmixer: list[str]
+    main: list[str] = field(default_factory=list)
+    guest: list[str] = field(default_factory=list)
+    remixer: list[str] = field(default_factory=list)
+    producer: list[str] = field(default_factory=list)
+    composer: list[str] = field(default_factory=list)
+    djmixer: list[str] = field(default_factory=list)
 
 
 def parse_artist_string(
@@ -39,7 +39,7 @@ def _split_tag(t: str | None) -> list[str]:
         dj, main = re.split(r" ?pres. ", main, maxsplit=1)
         li_dj.extend(_split_tag(dj))
     if main and " performed by " in main:
-        composer, main = re.split(r" ?performed by. ", main, maxsplit=1)
+        composer, main = re.split(r" ?performed by ", main, maxsplit=1)
         li_composer.extend(_split_tag(composer))
     if main:
         li_main.extend(_split_tag(main))
@@ -57,7 +57,7 @@ def _split_tag(t: str | None) -> list[str]:
 def format_artist_string(a: Artists, genres: list[str]) -> str:
     r = ";".join(a.producer + a.main + a.remixer)
     if a.composer and "Classical" in genres:
-        r = ";".join(a.composer) + " performed by. " + r
+        r = ";".join(a.composer) + " performed by " + r
     if a.djmixer:
         r = ";".join(a.djmixer) + " pres. " + r
     if a.guest:
diff --git a/rose/artiststr/__test__.py b/rose/artiststr/__test__.py
new file mode 100644
index 0000000..149828d
--- /dev/null
+++ b/rose/artiststr/__test__.py
@@ -0,0 +1,35 @@
+from rose.artiststr import Artists, format_artist_string, parse_artist_string
+
+
+def test_parse_artist_string() -> None:
+    assert parse_artist_string("A;B feat. C;D") == Artists(
+        main=["A", "B"],
+        guest=["C", "D"],
+    )
+    assert parse_artist_string("A pres. C;D") == Artists(
+        djmixer=["A"],
+        main=["C", "D"],
+    )
+    assert parse_artist_string("A performed by C;D") == Artists(
+        composer=["A"],
+        main=["C", "D"],
+    )
+    assert parse_artist_string("A pres. B;C feat. D;E") == Artists(
+        djmixer=["A"],
+        main=["B", "C"],
+        guest=["D", "E"],
+    )
+
+
+def test_format_artist_string() -> None:
+    assert format_artist_string(Artists(main=["A", "B"], guest=["C", "D"]), []) == "A;B feat. C;D"
+    assert format_artist_string(Artists(djmixer=["A"], main=["C", "D"]), []) == "A pres. C;D"
+    assert format_artist_string(Artists(composer=["A"], main=["C", "D"]), []) == "C;D"
+    assert (
+        format_artist_string(Artists(composer=["A"], main=["C", "D"]), ["Classical"])
+        == "A performed by C;D"
+    )
+    assert (
+        format_artist_string(Artists(djmixer=["A"], main=["B", "C"], guest=["D", "E"]), [])
+        == "A pres. B;C feat. D;E"
+    )