v0.5.0 · MIT · static analysis
VitestDedup reads your Vitest test files — never importing or executing them — and reports duplicate and near-duplicate tests: identical bodies hiding under different titles, structural copies that differ only in literals, whole suites repeated across files.
Every command shown on this site is real. Sample output is marked as illustrative.
$ npx vitest-dedup .vitest-dedup 0.5.0
duplicate-test (1 error)
error same normalized body under an equivalent context
--> tests/auth/login.spec.ts:14:1 redirects when signed out
related: tests/auth/session.spec.ts:22:1 same test
action: review removal or repair of intended coverage
near-duplicate-test (1 warning)
warning same behavior under an equivalent context
--> tests/api/users.spec.ts:8:1 lists admin users
related: tests/api/admin-users.spec.ts:31:1 similar
action: review before changing tests
318 tests in 42 files analyzed
errors: 1, warnings: 2, off: 0 · threshold: 0%
Analysis policy: FAIL
Detection time: 412.7 ms
Real command · output abridged and illustrative
npx vitest-dedup .
Copy-pasting a test and tweaking a value is the fastest way to add coverage today — and the slowest way to change anything tomorrow. As a suite grows, duplicated tests quietly pile up:
The analyzer's core judgment, in two sentences:
Two tests that do the same thing under different titles are duplicates. Two textually identical bodies that run under different hooks, mocks, or fixtures are not.
That distinction is why VitestDedup is an analysis tool rather than an auto-fixer. It names what each finding claims — a verdict with a remedy— and the decision to consolidate stays with you.
Features
No invented capabilities — each of these is shipped behavior ofv0.5.0, documented in thereference.
Tests are compared by normalized body, not title. Renamed copies get caught; identical bodies under different hooks, mocks, or fixtures are left alone.
Learn more →From exact duplicates and name collisions to parameterization candidates, subsumed tests, and redundant hooks — each with its own severity.
Learn more →Every finding names its remedy: redundant, consolidatable, name collision, or similar-uncertain. Rules configured off are not even computed.
Learn more →terminal for reading, jsonl for jq and agents, json for diffing runs, html for review, sarif for GitHub code scanning.
Learn more →Baseline existing debt and fail only on what a change adds. Scope a run to files changed since a revision, for pull requests.
Learn more →Your tests are read, never imported or executed. Vitest configuration is resolved statically, including monorepo project lists.
Learn more →Reports
Every finding carries a rule, a severity, a verdict, stable fingerprints, and full participant locations — the fields the json andsarif reporters write for machines.
rule duplicate-test · fingerprintduplicate-test:tests/auth/login.spec.ts:redirects-unauthenticated-users
two tests have the same normalized body under an equivalent context.
Action: review removal of one copy or repair of intended coverage.
rule parameterization-candidate · fingerprintparameterization-candidate:tests/cart/totals.spec.ts:applies-discount-code
same structure, differing only in literal values.
Action: preserve every case and assertion in one test.each table.
rule near-duplicate-test · fingerprintnear-duplicate-test:tests/api/users.spec.ts:lists-users-for-admin
same behavior under an equivalent context, but normalized bodies differ.
Action: review before changing tests; the usual outcome is one test.each table.
rule duplicate-test-name · fingerprintduplicate-test-name:tests/schemas/order.spec.ts:validates-payload
two tests in one file share a full title.
Action: rename one of the tests.
rule cross-file-duplicate · fingerprintcross-file-duplicate:tests/unit/format.spec.ts:formats-currency
duplicate-test criteria without the single-file restriction.
Action: review removal; duplication across unit and integration layers is sometimes deliberate.
rule redundant-hook · fingerprintredundant-hook:tests/db/repository.spec.ts:beforeEach-seed
a nested lifecycle hook repeats work an ancestor hook already performs.
Action: remove the nested hook.
Illustrative findings shaped after the documented JSON report fields (rule, verdict, participants, fingerprint). Not output generated by the CLI. Structured to consume real --reporters json output later without changing these components.
Workflow
A prebuilt binary for your platform arrives through optionalDependencies — no postinstall script, nothing compiled or executed at install time.
npm install --save-dev vitest-dedupDiscovery reads your Vitest configuration statically, then every test file is parsed and compared. Nothing is imported or run.
npx vitest-dedup .Each finding carries a verdict and an action. Deliberate parallels get a vitest-dedup-disable-next-line comment right in the test.
vitest-dedup . --reporters htmlRecord existing debt once, then fail only for what new work adds. In CI, the GitHub Action verifies the binary before running it.
vitest-dedup . --baseline dedup-baseline.jsonCommunity
Packages are published with npm trusted publishing, SHA-256 checksums, Sigstore signatures, and build provenance attestations — npm audit signatures verifies them.
Rust core, npm launcher, and the verification suite that gates every merge.
Bug reports and rule discussions. Check the existing list before opening a new one.
Start at CONTRIBUTING.md in the repository — verification, hooks, and coverage come first.
Concepts, configuration, CLI reference, and every reporter format.
Version history with per-release notes and links to the original GitHub releases.
Prebuilt binaries for macOS, Linux, and Windows, published with provenance attestations.