tests(parser): add midas lexer tests

tests/lexer/test_midas_lexer.py

@@ -0,0 +1,129 @@
+from typing import Any
+
+import pytest
+
+from lexer.midas import MidasLexer
+from lexer.token import Token, TokenType
+
+
+def scan(source: str) -> list[Token]:
+    return MidasLexer(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.LEFT_BRACE),
+        ("}", TokenType.RIGHT_BRACE),
+        (":", 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
+
+
+@pytest.mark.parametrize(
+    "src,expected",
+    [
+        ("+", TokenType.PLUS),
+        ("-", TokenType.MINUS),
+        ("*", TokenType.STAR),
+        ("/", TokenType.SLASH),
+        (">", TokenType.GREATER),
+        (">=", TokenType.GREATER_EQUAL),
+        ("<", TokenType.LESS),
+        ("<=", TokenType.LESS_EQUAL),
+        ("=", TokenType.EQUAL),
+        ("==", TokenType.EQUAL_EQUAL),
+        ("!=", TokenType.BANG_EQUAL),
+    ],
+)
+def test_operators(src: str, expected: TokenType):
+    tokens: list[Token] = scan(src)
+    assert_n_tokens(tokens, 1)
+    assert tokens[0].type == expected
+
+
+@pytest.mark.parametrize(
+    "src,expected",
+    [
+        ("a", TokenType.IDENTIFIER),
+        ("foo", TokenType.IDENTIFIER),
+        ("foo1", TokenType.IDENTIFIER),
+        ("foo_", TokenType.IDENTIFIER),
+        ("foo_bar1_baz2", TokenType.IDENTIFIER),
+        ("FOO_BAR1_BAZ2", TokenType.IDENTIFIER),
+        ("true", TokenType.TRUE),
+        ("false", TokenType.FALSE),
+        ("none", TokenType.NONE),
+    ],
+)
+def test_identifiers_keywords(src: str, expected: TokenType):
+    tokens: list[Token] = scan(src)
+    assert_n_tokens(tokens, 1)
+    assert tokens[0].type == expected
+
+
+@pytest.mark.parametrize(
+    "src,expected",
+    [
+        ("// This is a comment", TokenType.COMMENT),
+        ("/* This is a comment */", TokenType.COMMENT),
+        (" ", TokenType.WHITESPACE),
+        ("\t", TokenType.WHITESPACE),
+        ("\r", TokenType.WHITESPACE),
+        ("  \t  \t", TokenType.WHITESPACE),
+        ("\n", TokenType.NEWLINE),
+    ],
+)
+def test_misc(src: str, expected: TokenType):
+    tokens: list[Token] = scan(src)
+    assert_n_tokens(tokens, 1)
+    assert tokens[0].type == expected
+
+
+@pytest.mark.parametrize(
+    "src,expected_type,expected_value",
+    [
+        ("0", TokenType.NUMBER, 0),
+        ("0.0", TokenType.NUMBER, 0),
+        ("1234.56", TokenType.NUMBER, 1234.56),
+    ],
+)
+def test_literals(src: str, expected_type: TokenType, expected_value: Any):
+    tokens: list[Token] = scan(src)
+    assert_n_tokens(tokens, 1)
+    assert tokens[0].type == expected_type
+    assert tokens[0].value == expected_value
+
+
+def test_single_bang_error():
+    with pytest.raises(SyntaxError):
+        scan("!")
+
+
+@pytest.mark.parametrize(
+    "src",
+    [
+        "@",
+        '"',
+        "'",
+        ".",
+    ],
+)
+def test_unexpected_character(src: str):
+    with pytest.raises(SyntaxError):
+        scan(src)