Add tests for weasyl.forms.expect_id (#1459)

Reviewed-by: Charmander <~@charmander.me>

weasyl/test/test_forms.py

@@ -0,0 +1,39 @@
+import pytest
+
+from weasyl import forms
+from weasyl.error import WeasylError
+
+
+INVALID_IDS = (
+    '',
+    'a',
+    '0',
+    '-1',
+    '9999999999999999999999',
+    '\0',
+    '٨',
+    '+1',
+    pytest.param('01', marks=pytest.mark.xfail()),
+    '1.',
+    ' 1',
+    '1\n',
+    '0x1',
+    '1a',
+)
+
+VALID_IDS = (
+    ('1', 1),
+    ('10', 10),
+    ('2147483647', 2147483647),
+)
+
+
+@pytest.mark.parametrize('string', INVALID_IDS)
+def test_expect_id_invalid(string: str):
+    with pytest.raises(WeasylError):
+        forms.expect_id(string)
+
+
+@pytest.mark.parametrize('string,expected', VALID_IDS)
+def test_expect_id_valid(string: str, expected: int):
+    assert forms.expect_id(string) == expected