Duvet

Duvet is a tool that establishes a bidirectional link between implementation and specification. This practice is called requirements traceability, which is defined as:

the ability to describe and follow the life of a requirement in both a forwards and backwards direction (i.e., from its origins, through its development and specification, to its subsequent deployment and use, and through periods of ongoing refinement and iteration in any of these phases)

Quick Start

Before getting started, Duvet requires a rust toolchain.

1. Install command

   $ cargo install duvet --locked

2. Initialize repository

   In this example, we are using Rust. However, Duvet can be used with any language.

   $ duvet init --lang-rust --specification https://www.rfc-editor.org/rfc/rfc2324

3. Add a implementation comment in the project

   // src/lib.rs
   
   //= https://www.rfc-editor.org/rfc/rfc2324#section-2.1.1
   //# A coffee pot server MUST accept both the BREW and POST method
   //# equivalently.

4. Generate a report

   $ duvet report

Querying traceability state

duvet query is a development-time companion to duvet report. Where report produces the full traceability artifact for CI, query answers focused questions during development:

• Have I annotated the requirements I'm working on?
• Does my implementation have a test?
• Did the test actually execute the implementation?
• Are there duplicate annotations covering the same text?

Each question is a check (--check / -c), composable per invocation:

$ duvet query -c implementation,test --section my-spec.md
$ duvet query -c coverage -r 'target/jacoco/*.xml' -f jacoco-xml

The coverage check correlates test annotations with executed implementation annotations using a coverage report. For Java sources, duvet uses a verified two-phase coverage model that understands method declarations and other constructs that don't appear in bytecode-based coverage data; for other languages it uses a verified degraded model that reads coverage directly at the annotation's target line.

See the guide for the full reference.

Development

You must have git lfs installed. You can check this by running

git lfs version

Building

$ cargo xtask build

Testing

$ cargo xtask test

Verifying the coverage model

The two-phase coverage model in duvet-coverage is formally verified with Verus. CI runs the verifier on every push and PR. To verify locally:

1. Download the pinned Verus release. The version that matches vstd in Cargo.lock is in .github/workflows/ci.yml as VERUS_VERSION. Verus ships pre-built binaries for x86_64 Linux, x86_64 macOS, arm64 macOS, and x86_64 Windows; pick the one for your host:

   $ VERUS_VERSION="0.2026.05.24.ecee80a"
   $ curl -L -o verus.zip \
       "https://github.com/verus-lang/verus/releases/download/release%2F${VERUS_VERSION}/verus-${VERUS_VERSION}-x86-linux.zip"
   $ unzip -q verus.zip

   The archive extracts to verus-x86-linux/ (or -x86-macos, etc.) and contains the verus and cargo-verus binaries, the bundled z3 solver, and the vstd standard library.

2. Add the directory to PATH.

   $ export PATH="$PWD/verus-x86-linux:$PATH"

3. Install the Rust toolchain Verus needs. The first time verus runs, it prints the exact rustup install command for the toolchain it pins. Run that command:

   $ verus
   verus: required rust toolchain X.Y.Z-x86_64-unknown-linux-gnu not found
   run the following command (in a bash-compatible shell) to install the necessary toolchain:
     rustup install X.Y.Z-x86_64-unknown-linux-gnu
   ...
   $ rustup install X.Y.Z-x86_64-unknown-linux-gnu

   On macOS, you may also need to clear the Gatekeeper quarantine on the binaries; the archive includes macos_allow_gatekeeper.sh.

4. Verify the proofs.

   $ cargo verus build -p duvet-coverage --features verify

   Expected output: verified N functions, 0 errors. A non-zero error count indicates a regression in the proofs.

   The verify feature is what pulls in vstd. It is off by default so that vstd stays out of the published dependency graph — every vstd path in duvet-coverage is ghost, so a plain cargo build erases all of them. Omitting --features verify here will fail with unresolved vstd imports.

The Verus prebuilt binary (and the z3 it bundles) are built against glibc 2.34+ / 2.31+, so older distributions (Amazon Linux 2, Ubuntu 20.04, CentOS 7) cannot run them. On those hosts, build Verus — and, if its prebuilt z3 also won't start, z3 — from source so they link against the local glibc (see Verus's BUILD.md: vargo build --release, then put source/target-verus/release on PATH).

A from-source z3 reports a build-hash-suffixed SMT version string that the verifier rejects by default. It is still the pinned z3 version, so results are identical; pass the (supported) flag to skip the cosmetic check — vargo build accepts --no-solver-version-check, and the verify step uses the -V form:

$ cargo verus build -p duvet-coverage --features verify -- -V no-solver-version-check

Otherwise, rely on CI for verification.

Security

See CONTRIBUTING for more information.

License

This project is licensed under the Apache-2.0 License.