Design: Test Coverage Improvement (74% → 80%, stretch 90%)

Status: Superseded by 0044-coverage_improvement_2026q2

Summary

This doc planned restoring line coverage to 80%+ (with a 90% stretch) after the filter-support merge dropped it to ~74%. The plan excluded vendored third_party/ code from the metric and added targeted tests across the text engine, renderer backends, rendering context, the filter executor, and previously untested SVG element types.

That work is done. Repo-wide line coverage is now 85.63% (past this doc's 80% target), and the specific test files this plan called for have landed — e.g. TextEngine_tests.cc and dedicated SVGSVGElement_tests.cc / SVGImageElement_tests.cc / SVGUseElement_tests.cc / SVGTextPathElement_tests.cc / SVGStopElement_tests.cc / SVGLineElement_tests.cc. Ongoing coverage work is tracked in 0044-coverage_improvement_2026q2.

The original full plan (per-subsystem coverage tables, per-phase test checklists, and the Round 1 results) is recoverable from git history.