Test Coverage Goal - March 2026 - Target: 52% (Python bootstrap layer)

[github-actions]

📊 Test Coverage Status Report

Analysis Date: 2026-03-23
Current Coverage: Effectively 0% on Python layer (no Python test files exist)
Target for Month: Add meaningful test coverage to the Python bootstrap layer

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🔍 Coverage Reality Check

The test-coverage-improver workflow references a 44% coverage figure, but a codebase audit reveals important context:

Layer	Status
Rust (primary)	242 source files, 19,366+ lines of tests — Rust CI runs cargo test --all
Python bootstrap	2 source files (247 lines) — zero test files exist
Coverage tooling	No .coveragerc, no coverage.xml, no pytest configured

The 44% figure likely reflects Rust test coverage (via cargo test) rather than Python pytest coverage. The Python layer has 0% measurable coverage because no Python tests run in CI.

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🎯 Priority Test Targets for March 2026

src/azlin/rust_bridge.py (225 lines — 0% covered)

This is the critical Python entry point. It has complex logic for finding/installing the Rust binary:

Function	Lines	Complexity	Priority
_platform_suffix()	16	Low	🟡 Medium
_is_rust_binary()	11	Low	🟡 Medium
_find_rust_binary()	15	Medium	🔴 Critical
_download_from_release()	68	High	🔴 Critical
_build_from_source()	27	Medium	🔴 Critical
_exec_rust()	7	Low	🟡 Medium
entry()	32	Medium	🔴 Critical

Note: PR #885 adds tests/unit/test_rust_bridge.py with 7 tests — this is the right foundation! Merge it to start coverage tracking.

src/azlin/__init__.py (22 lines — trivial, MI score 100)

Simple package metadata — low priority, but easy wins for coverage percentage.

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📋 March 2026 Testing Checklist

Foundation Setup (prerequisite)

• Merge PR fix(security): harden tar extraction in rust_bridge against path traversal (#876) #885 (adds tests/unit/test_rust_bridge.py — 7 tests)
• Add pytest + pytest-cov to [dependency-groups].dev in pyproject.toml
• Add coverage configuration to pyproject.toml:

  [tool.coverage.run]
  source = ["src/azlin"]
  branch = true
  
  [tool.coverage.report]
  exclude_lines = ["if __name__ == .__main__.", "pragma: no cover"]

• Update rust-ci.yml or ci.yml to run Python tests with coverage:

  - name: Python tests
    run: python -m pytest tests/unit/ --cov=src/azlin --cov-report=xml

High-Priority Tests (rust_bridge.py)

• _platform_suffix(): Test all 5 platform/arch combinations (linux x86_64, linux aarch64, macOS x86_64, macOS arm64, Windows, unknown)
• _find_rust_binary(): Test found-at-each-candidate-path, none-found, non-executable skipped
• _download_from_release(): Test download success, API failure, no matching asset, extraction error
• _build_from_source(): Test cargo-not-found, cargo-success, cargo-failure
• entry(): Test full bootstrap flow (found, download, build, all-fail)

Medium-Priority Tests

• _is_rust_binary(): Test subprocess success/failure/timeout
• _exec_rust(): Test Windows path (subprocess) vs Unix path (execvp)

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🛠️ Testing Approach

All external calls must be mocked (no real network/filesystem):

# Example: Test platform detection
from unittest.mock import patch
from azlin.rust_bridge import _platform_suffix

def test_platform_suffix_linux_x86_64():
    with patch("platform.system", return_value="Linux"), \
         patch("platform.machine", return_value="x86_64"):
        assert _platform_suffix() == "linux-x86_64"

def test_platform_suffix_unknown_returns_none():
    with patch("platform.system", return_value="FreeBSD"), \
         patch("platform.machine", return_value="x86_64"):
        assert _platform_suffix() is None

# Example: Test binary discovery
from unittest.mock import patch, MagicMock
from azlin.rust_bridge import _find_rust_binary

def test_find_binary_returns_managed_path_when_valid(tmp_path):
    fake_bin = tmp_path / "azlin"
    fake_bin.touch()
    with patch("azlin.rust_bridge.MANAGED_BIN", fake_bin), \
         patch("os.access", return_value=True), \
         patch("azlin.rust_bridge._is_rust_binary", return_value=True):
        result = _find_rust_binary()
        assert result == str(fake_bin)

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📈 Coverage Progress Tracker

Week	Coverage %	Tests Added	Notes
2026-03-23	~0% (baseline)	0	No Python tests in CI
Target end of March	52%+	15–20	Bootstrap layer covered

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🔗 Related

• PR fix(security): harden tar extraction in rust_bridge against path traversal (#876) #885: fix/issue-876-rust-bridge-security-hardening — includes initial test_rust_bridge.py
• Issue bug: tarfile extraction without filter='data' in rust_bridge.py #876: tarfile security fix (motivates testing the download path)
• test-coverage-improver.md workflow: configured to run weekly and on Python PRs

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Next Month Preview

Once the Python bootstrap is covered, consider adding Rust coverage reporting via cargo-tarpaulin or cargo-llvm-cov to track the actual coverage of the primary codebase. The 19,366+ lines of Rust tests deserve visibility in coverage metrics too.

Generated by Test Coverage Improvement Tracker