tests(parser): add basic lexer test

add a basic test for the annotation lexer to check punctuation tokens

tests/lexer/test_annotation_lexer.py

@@ -0,0 +1,26 @@
+import pytest
+
+from lexer.annotations import AnnotationLexer
+from lexer.token import Token, TokenType
+
+
+def scan(source: str) -> list[Token]:
+    return AnnotationLexer(source).process()
+
+def assert_n_tokens(tokens: list[Token], n: int):
+    assert len(tokens) == n + 1
+    assert tokens[-1].type == TokenType.EOF
+
+@pytest.mark.parametrize("src,expected", [
+    ("(", TokenType.LEFT_PAREN),
+    (")", TokenType.RIGHT_PAREN),
+    ("[", TokenType.LEFT_BRACKET),
+    ("]", TokenType.RIGHT_BRACKET),
+    (":", TokenType.COLON),
+    (",", TokenType.COMMA),
+    ("_", TokenType.UNDERSCORE),
+])
+def test_punctuation(src: str, expected: TokenType):
+    tokens: list[Token] = scan(src)
+    assert_n_tokens(tokens, 1)
+    assert tokens[0].type == expected