Add test coverage for stac_api_io.py error handling

- Test decode error in request() method
- Test write to URL error in write_text_to_href()
- Test unknown STAC object type error in stac_object_from_dict()

Author: nlebovits

tests/test_stac_api_io.py

@@ -1,5 +1,6 @@
 import typing
 from pathlib import Path
+from typing import Any
 from urllib.parse import parse_qs, urlsplit
 
 import pystac
@@ -289,3 +290,58 @@ def test_stac_io_in_pystac() -> None:
     stac_io = root._stac_io
     assert isinstance(stac_io, StacApiIO)
     assert stac_io.timeout == 42
+
+
+def test_request_decode_error(requests_mock: Mocker) -> None:
+    """Test that decode errors in request() are properly handled."""
+    url = "https://example.com/bad-encoding"
+    # Mock a response with invalid UTF-8 content
+    requests_mock.get(url, status_code=200, content=b"\xff\xfe\x00\x00")
+
+    stac_api_io = StacApiIO()
+
+    with pytest.raises(APIError) as excinfo:
+        stac_api_io.request(url)
+
+    assert (
+        "decode" in str(excinfo.value).lower() or "utf-8" in str(excinfo.value).lower()
+    )
+
+
+def test_write_text_to_href_url_error() -> None:
+    """Test that write_text_to_href raises APIError for URLs."""
+    stac_api_io = StacApiIO()
+
+    with pytest.raises(APIError, match="Transactions not supported"):
+        stac_api_io.write_text_to_href("https://example.com/write", "content")
+
+
+def test_stac_object_from_dict_unknown_type(monkeypatch: MonkeyPatch) -> None:
+    """Test that unknown STAC object types raise ValueError."""
+    stac_api_io = StacApiIO()
+
+    import json
+
+    with open("tests/data/planetary-computer-collection.json") as f:
+        real_stac_data = json.load(f)
+
+    # Mock identify_stac_object to return an unknown type
+    class MockInfo:
+        object_type = "UNKNOWN_TYPE"
+
+    def mock_identify_stac_object(d: dict[str, Any]) -> MockInfo:
+        return MockInfo()
+
+    # Mock migrate_to_latest to just return the data unchanged
+    def mock_migrate_to_latest(d: dict[str, Any], info: MockInfo) -> dict[str, Any]:
+        return d
+
+    monkeypatch.setattr(
+        "pystac_client.stac_api_io.identify_stac_object", mock_identify_stac_object
+    )
+    monkeypatch.setattr(
+        "pystac_client.stac_api_io.migrate_to_latest", mock_migrate_to_latest
+    )
+
+    with pytest.raises(ValueError, match="Unknown STAC object type"):
+        stac_api_io.stac_object_from_dict(real_stac_data)