Add direct coverage for GitHub Project GraphQL mutations and pagination

[codeforester]

Goal

Add direct, hermetic tests for the GitHub Project GraphQL data-access paths so malformed mutation payloads, pagination regressions, and failure translation are caught before basectl gh project changes a live Project.

Background

A fresh coverage run on current main (685d538) passed all 1,051 Python tests and the repository ratchet at 88.12% statements, 77.67% branches, and 85.55% combined coverage. The hosted Python 3.10-3.13 jobs reported the same statement result and at least 77.62% branch / 85.53% combined coverage.

The aggregate result hides the largest package-level gap. base_github_projects is at 78.44% statement and 64.49% branch coverage. Its lowest-covered modules include:

• engine.py: 53.28% statements, 27.27% branches, 48.00% combined.
• project_graphql.py: 56.25% statements, 25.00% branches, 50.00% combined.
• project_item_fields.py: 67.21% statements, 52.27% branches, 63.25% combined.
• project_git.py: 75.68% statements, 50.00% branches, 68.63% combined.

The uncovered engine.py paths include the mutations and cursor loops used to create, copy, update, link, and backfill GitHub Projects. These are live mutation boundaries where an argument or pagination defect can affect real repository planning state even while the repo-wide coverage floor remains green.

Scope

• Add mocked unit tests for fetch_project_repository_names, fetch_repository_issues, and fetch_project_issue_content_ids, including single-page and multi-page responses.
• Cover mutation payloads and response parsing for project create/copy/update, single-select field create/update, repository linking, issue backfill, and item updates.
• Cover missing-node, missing-repository, missing-issue, authentication, scope, timeout, and GraphQL error translation where those branches are currently untested.
• Cover project_item_fields.py pagination plus copy/default planning and application, including skipped missing fields/options and preservation of existing values.
• Keep all tests hermetic by mocking the GitHub CLI/GraphQL boundary; do not require credentials or mutate a live Project.

Acceptance Criteria

• Every cursor loop listed in Scope has direct single-page and multi-page coverage and verifies cursor progression and termination.
• Project and field mutation helpers assert the exact GraphQL variables sent and the parsed return value or error.
• Item-copy/default tests prove existing non-empty values are preserved and missing fields/options are reported rather than silently dropped.
• base_github_projects reaches at least 85% statement coverage and 75% branch coverage without excluding additional production files.
• The repository statement, branch, and combined coverage ratchets remain enabled and pass.

Validation

BASE_CLI_SOURCE_DIR=../base-cli/lib/python \
PYTHONPATH=../base-cli/lib/python:lib/python:cli/python \
python -m pytest cli/python/base_github_projects/tests -q

BASE_CLI_SOURCE_DIR=../base-cli/lib/python \
PYTHONPATH=../base-cli/lib/python:lib/python:cli/python \
python -m pytest --cov=cli/python --cov-report=term-missing --cov-report=json:coverage.json
python -m tests.coverage_gate coverage.json

BASE_BASH_LIBS_DIR=../base-bash-libs/lib/bash \
BASE_CLI_SOURCE_DIR=../base-cli/lib/python \
env -u BASE_HOME ./bin/base-test

Non-Goals

• Calling or mutating a live GitHub Project from unit tests.
• Refactoring the Project command architecture or changing public command behavior.
• Requiring 100% coverage or covering generated/static GraphQL query strings for their own sake.

Project Fields

• Status: Ready
• Priority: P2
• Area: Python
• Initiative: Contract Hardening
• Size: M

Agent Assignment

Copilot candidate after triage. The GraphQL boundary is mockable and the expected request/response contracts are explicit; a human should still review the mutation assertions before merge.