ZeroCov

Problem. Every engineering team has deferred tests: "we'll write tests next sprint." Months later, authentication, expense handling, and approval workflows have zero coverage, and fixing that by hand is a two-to-three-week project. The root cause is tooling: existing AI assistants suggest test lines, but none can read a specification, plan a layered strategy, run the suite, and repair the source when the tests and the contract disagree. Solution. ZeroCov is a six-step workflow executed by IBM Bob 2.0 on a real-shaped Node.js/TypeScript REST API (ExpenseFlow). Step 1 — Bob reads openapi.yaml, docs/auth-security-requirements.md and docs/approval-workflow.md, then measures the baseline: 22.77% statements, 14 tests. Step 2 — Plan mode writes TEST-STRATEGY.md, risk-ranking modules and assigning test layers; a human approves before any code. Step 3 — four subagents (auth, API, integration, utils) write spec-driven tests in parallel, each with isolated context. Step 4 — Agent mode runs pnpm test:coverage, reads failures, and fixes the source until green. Step 5 — COVERAGE-REPORT.md documents the delta and every finding. Step 6 — the session diff becomes a reviewable pull request. Result. 145 tests across 9 suites; 89.46% statement and 91.57% line coverage, up from 22.77% / 25.36%. Eight tests fail at the test commit and pass after two source fixes: the auth middleware now returns 401 for every token verification failure (EXP-TOKEN-401), and expense amount validation reuses the shared validator, enforcing integer, finite, positive, capped amounts per openapi.yaml. No assertion was weakened to make a test pass. Target users. Developers assigned to reduce test debt before a release, teams adding coverage gates to CI, and engineers onboarding to an untested service. They interact with it through IBM Bob IDE: attach the specs, approve the strategy, let subagents execute, review the diff. Why it is different. (1) Tests are derived from the contract, not from current behavior, so divergences surface as failures instead of being blessed; (2) parallelism is real — four isolated subagents cover four layers in one wall-clock; (3) the red-to-green sequence is auditable in git: tests land first, fixes second; (4) a project rule forbids weakening an assertion to match a bug, and the rule is enforced across all subagents. Efficiency. The session takes about 25 minutes versus a 2–3 week manual estimate. Reproduction is one command on a baseline tag, and captured evidence is in the repository: docs/coverage-before.txt, docs/red-state-failures.txt, docs/coverage-after.txt, plus Bob task session screenshots in bob_sessions/. Honesty note. ExpenseFlow is a synthetic fixture; the two divergences were seeded deliberately so the workflow is demonstrable and fully reproducible end to end. The deliverable is the workflow — the defects exist to prove it works.