Add tests for spec parsing

Signed-off-by: Tushar Goel <tushar.goel.dav@gmail.com>

Author: TG1999

src/packageurl/__init__.py

@@ -463,6 +463,10 @@ def from_string(cls, purl: str) -> Self:
         type_, sep, remainder = remainder.partition("/")
         if not type_ or not sep:
             raise ValueError(f"purl is missing the required type component: {purl!r}.")
+        
+        # check if type starts with a number
+        if type_[0] in string.digits:
+            raise ValueError(f"purl type cannot start with a number: {type_!r}.")
 
         type_ = type_.lower()
 

tests/test_purl_spec.py

@@ -0,0 +1,58 @@
+import json
+import os
+
+import pytest
+
+from packageurl import PackageURL
+
+current_dir = os.path.dirname(__file__)
+root_dir = os.path.abspath(os.path.join(current_dir, ".."))
+spec_file_path = os.path.join(root_dir, "spec", "tests", "spec", "specification-test.json")
+
+valid_purl_types_file = os.path.join(root_dir, "spec", "purl-types-index.json")
+
+
+with open(spec_file_path, "r", encoding="utf-8") as f:
+    test_cases = json.load(f)
+
+with open(valid_purl_types_file, "r", encoding="utf-8") as f:
+    valid_purl_types = json.load(f)
+
+tests = test_cases["tests"]
+
+parse_tests = [t for t in tests if t["test_type"] == "parse"]
+build_tests = [t for t in tests if t["test_type"] == "build"]
+
+@pytest.mark.parametrize("description, input_str, expected_output, expected_failure", [
+    (t["description"], t["input"], t["expected_output"], t["expected_failure"])
+    for t in parse_tests
+])
+def test_parse(description, input_str, expected_output, expected_failure):
+    if expected_failure:
+        with pytest.raises(Exception):
+            PackageURL.from_string(input_str)
+    else:
+        result = PackageURL.from_string(input_str)
+        assert result.to_string() == expected_output
+
+
+@pytest.mark.parametrize("description, input_dict, expected_output, expected_failure", [
+    (t["description"], t["input"], t["expected_output"], t["expected_failure"])
+    for t in build_tests
+])
+def test_build(description, input_dict, expected_output, expected_failure):
+    kwargs = {
+        "type": input_dict.get("type"),
+        "namespace": input_dict.get("namespace"),
+        "name": input_dict.get("name"),
+        "version": input_dict.get("version"),
+        "qualifiers": input_dict.get("qualifiers"),
+        "subpath": input_dict.get("subpath"),
+    }
+
+    if expected_failure:
+        with pytest.raises(Exception):
+            PackageURL(**kwargs).to_string()
+    else:
+        purl = PackageURL(**kwargs)
+        assert purl.to_string() == expected_output