PYTHON-5727 Add tests for __main__ blocks

[aclark4life]

PYTHON-5727

Changes in this PR

Adds test coverage for the previously untested __main__ block in pymongo/uri_parser.py.

A new TestMainBlock class in test/test_uri_parser.py launches the module as a script via subprocess (python -m pymongo.uri_parser <uri>) and covers both branches:

• a valid URI is parsed and pretty-printed to stdout
• an invalid URI is caught and its error message printed

Both cases assert a clean (0) exit code.

Note: pymongo/daemon.py — the other module named in the ticket — already has TestMainBlock coverage on master. A repo-wide search confirmed these are the only two __main__ blocks in pymongo/, bson/, and gridfs/.

Test Plan

• python -m pytest test/test_uri_parser.py::TestMainBlock test/test_daemon.py::TestMainBlock -v passes.
• The new tests exercise the __main__ block end-to-end through a real subprocess, so coverage.py subprocess measurement will capture it.

Checklist

Checklist for Author

• Did you update the changelog (if necessary)? N/A — test-only change.
• Is there test coverage?
• Is any followup work tracked in a JIRA ticket? If so, add link(s). N/A

Checklist for Reviewer

• Does the title of the PR reference a JIRA Ticket?
• Do you fully understand the implementation? (Would you be comfortable explaining how this code works to someone else?)
• Is all relevant documentation (README or docstring) updated?

[Copilot]

Pull request overview

Adds end-to-end test coverage for the pymongo.uri_parser module’s __main__ block by executing it as a real module in a subprocess, ensuring both the success path (pretty-printed parsed result) and the handled error path (InvalidURI) are exercised.

Changes:

• Add subprocess-based tests that run python -m pymongo.uri_parser <uri> and assert expected stdout content.
• Cover both valid URI parsing output and invalid URI error message output while confirming exit code 0.