Programming language: Rust
License: Apache License 2.0
Latest version: v0.22.0

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Build Status Latest Version License:MIT Docker Developers Wiki

Tarpaulin is a code coverage reporting tool for the Cargo build system, named for a waterproof cloth used to cover cargo on a ship. Currently, tarpaulin provides working line coverage and while fairly reliable may still contain minor inaccuracies in the results. A lot of work has been done to get it working on a wide range of projects, but often unique combinations of packages and build features can cause issues so please report anything you find that's wrong. Also, check out our roadmap for planned features.

On Linux Tarpaulin's default tracing backend is still Ptrace and will only work on x86_64 processors. This can be changed to the llvm coverage instrumentation with --engine llvm, for Mac and Windows this is the default collection method.

It can also be run in Docker, which is useful for when you don't use Linux but want to run it locally, e.g. during development. See below for how to do that.

Below is the help-text for a thorough explanation of the flags and features available:

cargo-tarpaulin version: 0.22.0
Tool to analyse test coverage of cargo projects

    cargo tarpaulin [FLAGS] [OPTIONS] [-- <args>...]

        --all                      Alias for --workspace (deprecated)
        --all-features             Build all available features
        --all-targets              Test all targets
        --avoid-cfg-tarpaulin      Remove --cfg=tarpaulin from the RUSTFLAG
        --benches                  Test all benches
        --bins                     Test all binaries
    -b, --branch                   Branch coverage: NOT IMPLEMENTED
        --count                    Counts the number of hits during coverage
        --debug                    Show debug output - this is used for diagnosing issues with tarpaulin
        --doc                      Test only this library's documentation
        --dump-traces              Log tracing events and save to a json file. Also, enabled when --debug is used
        --examples                 Test all examples
        --follow-exec              Follow executed processes capturing coverage information if they're part of your
        --force-clean              Adds a clean stage to work around cargo bugs that may affect coverage results
    -f, --forward                  Forwards unexpected signals to test. This is now the default behaviour
        --frozen                   Do not update Cargo.lock or any caches
    -h, --help                     Prints help information
        --ignore-config            Ignore any project config files
        --ignore-panics            Ignore panic macros in tests
        --ignore-tests             Ignore lines of test functions when collecting coverage (default)
    -i, --ignored                  Run ignored tests as well
        --implicit-test-threads    Don't supply an explicit `--test-threads` argument to test executable. By default
                                   tarpaulin will infer the default rustc would pick if not ran via tarpaulin and set it
        --include-tests            Include lines of test functions when collecting coverage
        --lib                      Test only this package's library unit tests
    -l, --line                     Line coverage
        --locked                   Do not update Cargo.lock
        --no-default-features      Do not include default features
        --no-fail-fast             Run all tests regardless of failure
        --no-run                   Compile tests but don't run coverage
        --offline                  Run without accessing the network
        --print-rust-flags         Print the RUSTFLAGS options that tarpaulin will compile your program with and exit
        --print-rustdoc-flags      Print the RUSTDOCFLAGS options that tarpaulin will compile any doctests with and exit
        --release                  Build in release mode.
        --skip-clean               The opposite of --force-clean
        --tests                    Test all tests
    -V, --version                  Prints version information
    -v, --verbose                  Show extra output
        --workspace                Test all packages in the workspace

    -Z <FEATURES>...                   List of unstable nightly only flags
        --bench <NAME>...              Test only the specified bench target
        --bin <NAME>...                Test only the specified binary
        --ciserver <SERVICE>           Name of service, supported services are:
                                       travis-ci, travis-pro, circle-ci, semaphore, jenkins and codeship.
                                       If you are interfacing with coveralls.io or another site you can also specify a
                                       name that they will recognise. Refer to their documentation for this.
        --color <WHEN>                 Coloring: auto, always, never [possible values: Auto, Always, Never]
        --command <CMD>                cargo subcommand to run. So far only test and build are supported [possible
                                       values: Test, Build]
        --config <FILE>                Path to a toml file specifying a list of options this will override any other
                                       options set
        --coveralls <KEY>              Coveralls key, either the repo token, or if you're using travis use
                                       $TRAVIS_JOB_ID and specify travis-{ci|pro} in --ciserver
        --engine <ENGINE>              Coverage tracing backend to use [possible values: Auto, Ptrace, Llvm]
        --example <NAME>...            Test only the specified example
    -e, --exclude <PACKAGE>...         Package id specifications to exclude from coverage. See cargo help pkgid for more
        --exclude-files <FILE>...      Exclude given files from coverage results has * wildcard
        --fail-under <PERCENTAGE>      Sets a percentage threshold for failure ranging from 0-100, if coverage is below
                                       exit with a non-zero code
        --features <FEATURES>...       Features to be included in the target project
    -j, --jobs <N>                     Number of parallel jobs, defaults to # of CPUs
        --manifest-path <PATH>         Path to Cargo.toml
    -o, --out <FMT>...                 Output format of coverage report [possible values: Json, Stdout, Xml, Html, Lcov]
        --output-dir <PATH>            Specify a custom directory to write report files
    -p, --packages <PACKAGE>...        Package id specifications for which package should be build. See cargo help pkgid
                                       for more info
        --post-test-delay <SECONDS>    Delay after test to collect coverage profiles
        --profile <NAME>               Build artefacts with the specified profile
        --report-uri <URI>             URI to send report to, only used if the option --coveralls is used
    -r, --root <DIR>                   Calculates relative paths to root directory. If --manifest-path isn't specified
                                       it will look for a Cargo.toml in root
        --run-types <TYPE>...          Type of the coverage run [possible values: Tests, Doctests, Benchmarks, Examples,
                                       Lib, Bins, AllTargets]
        --rustflags <FLAGS>            rustflags to add when building project (can also be set via RUSTFLAGS env var)
        --target <TRIPLE>              Compilation target triple
        --target-dir <DIR>             Directory for all generated artifacts
        --test <NAME>...               Test only the specified test target
    -t, --timeout <SECONDS>            Integer for the maximum time in seconds without response from test before timeout
                                       (default is 1 minute).

    <args>...    Arguments to be passed to the test executables can be used to filter or skip certain tests

Note on tests using signals

If your tests or application make use of unix signals they may not work with tarpaulin. This is because tarpaulin relies on the sigtrap signal to catch when the instrumentation points are hit. The --forward option results in forwarding the signals from process stops not caused by SIGSTOP, SIGSEGV or SIGILL to the test binary.


Below is a list of features currently implemented. As Tarpaulin loads binary files into memory and parses the debugging information, different setups could lead to coverage not working. In this instance, please raise an issue detailing your setup and an example project and I'll attempt to fix it (please link us to a repo and the commit containing your project and paste the verbose output).

  • Line coverage
  • Full compatibility with cargo test CLI arguments
  • Uploading coverage to https://coveralls.io or https://codecov.io
  • HTML report generation and other coverage report types
  • Coverage of tests, doctests, benchmarks and examples possible
  • Excluding irrelevant files from coverage
  • Config file for mutually exclusive coverage settings (see Config file section for details)



Tarpaulin is a command-line program, you install it into your linux development environment with cargo install:

cargo install cargo-tarpaulin

Tarpaulin used to rely on Cargo as a dependency and then require an ssl install as well as other libraries but now it uses your system cargo simplifying the installation and massively reducing the install time on CI.

When using the Nix package manager, the nixpkgs.cargo-tarpaulin package can be used. This ensures that tarpaulin will be built with the same rust version as the rest of your packages.

You can also use cargo-binstall:

cargo binstall cargo-tarpaulin

Environment Variables

When tarpaulin runs your tests it strives to run them in the same environment as if they were ran via cargo test. In order to achieve this it sets the following environment variables when executing the test binaries:

  • RUST_BACKTRACE - When --verbose flag is used
  • CARGO_MANIFEST_DIR - Path to Cargo.toml From --root | --manifest-path or guessed from the current or parent directory
  • CARGO_PKG_NAME - From Cargo.toml
  • CARGO_PKG_AUTHORS - From Cargo.toml
  • CARGO_PKG_VERSION - From Cargo.toml
  • LLVM_PROFILE_FILE - Used for LLVM coverage

Cargo Manifest

In order for tarpaulin to construct the Cargo environment correctly, tarpaulin needs to find Cargo.toml by either:

  • Using --root or --manifest-path or
  • By invoking Cargo from the current working directory within the project holding Cargo.toml manifest or
  • By invoking Cargo from a sub-directory within the project

If Cargo does not find any Cargo.toml from using either of above methods the run will error "cargo metadata" and exit.

Several RFCs are open in rust-lang to expose more of these directly in order to avoid the issues arising out of this.

Command line

To get detailed help on available arguments when running tarpaulin call:

cargo tarpaulin --help

Currently no options are required, if no root directory is defined Tarpaulin will run in the current working directory.

Below is a Tarpaulin run utilising one of our example projects. This is a relatively simple project to test and if you check the test, you can see the output correctly reports the lines the test hits.

cargo tarpaulin -v
[INFO tarpaulin] Running Tarpaulin
[INFO tarpaulin] Building project
    Finished dev [unoptimized + debuginfo] target(s) in 0.00s
[DEBUG tarpaulin] Processing simple_project
[INFO tarpaulin] Launching test
[INFO tarpaulin] running /home/xd009642/code/rust/tarpaulin/tests/data/simple_project/target/debug/deps/simple_project-b0accf6671d080e0

running 1 test
test tests::bad_test ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

[INFO tarpaulin] Coverage Results:
|| Uncovered Lines:
|| src/lib.rs: 6
|| src/unused.rs: 4-6
|| Tested/Total Lines:
|| src/lib.rs: 5/6
|| src/unused.rs: 0/3
55.56% coverage, 5/9 lines covered

Tarpaulin can also report the change in coverage for each file between runs. If the tests were updated in the previous example to cover all the lines we would expect the following output.

cargo tarpaulin -v
[INFO tarpaulin] Running Tarpaulin
[INFO tarpaulin] Building project
    Finished dev [unoptimized + debuginfo] target(s) in 0.00s
[DEBUG tarpaulin] Processing simple_project
[INFO tarpaulin] Launching test
[INFO tarpaulin] running /home/xd009642/code/rust/tarpaulin/tests/data/simple_project/target/debug/deps/simple_project-b0accf6671d080e0

running 1 test
test tests::bad_test ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

[INFO tarpaulin] Coverage Results:
|| Tested/Total Lines:
|| src/lib.rs: 6/6 +16.67%
|| src/unused.rs: 3/3 +100%
100% coverage, 9/9 lines covered, +44.44% change in coverage

Hint: if using coveralls.io with travis-ci run with the options --ciserver travis-ci --coveralls $TRAVIS_JOB_ID. The coveralls.io repo-token is mainly designed for private repos and it won't generate a badge for the coverage results submitted (although you can still see them on the coveralls web interface). For an example of a project using Tarpaulin, you can check out my crate keygraph-rs.

Ignoring code in files

Before tarpaulin 0.13.4 you could ignore code in blocks with #[cfg_attr(tarpaulin, skip)] this has changed with 0.13.4 and onwards and the new instructions are described below. If you get compiler errors mentioning unknown attribute skip use the --avoid-cfg-tarpaulin flag, this affects a small number of users as it wasn't a largely adopted feature so also look to updating your code or seeing if any of your dependencies are out of date.

Tarpaulin allows you to ignore modules or functions using attributes. Below is an example of ignoring the main function in a project:

fn main() {
    println!("I won't be included in results");

// Also supports the rustc `no_coverage` attribute.
fn not_included() {


However, the skip attribute only allows you to exclude code from coverage it doesn't change the code present in the binaries or what tests are ran. Because of this, --cfg=tarpaulin is used when building your project for Tarpaulin allowing you to also conditionally include/exclude code from compilation entirely. For example to have a test that isn't included in the test binaries when built with tarpaulin and cannot be ran just do:

fn big_test_not_for_tarpaulin() {
    // Something that would be very slow in tarpaulin or not work

If you still want the test included in the binary just ignored by default you can use:

#[cfg_attr(tarpaulin, ignore)]
fn ignored_by_tarpaulin() {


There is also nightly support for using tool attributes with tarpaulin for skip. For example:


fn main() {
    println!("I won't be in coverage stats");


As Tarpaulin changes the RUSTFLAGS when building tests sometimes rebuilds of test binaries can't be avoided. There is also a --clean and --skip-clean argument, the default has been changed at times to avoid issues with incremental compilation when changing RUSTFLAGS. If you aim to reduce the amount of unnecessary recompilation attempting to add the --skip-clean flag should be the first step. After that you can either:

  1. Use cargo tarpaulin --print-rust-flags and use those flags for dev and coverage
  2. Use --target-dir when running tarpaulin and have a coverage build and dev build

Continuous Integration Services

Tarpaulin aims to be easy to add to your CI workflow. With well tested support for Travis-CI it also supports sending CI specific meta-data to coveralls.io for Circle, Semaphore, Jenkins and Codeship (though only Jenkins has been tested).

You can also use Tarpaulin on Azure, check out crate-ci/azure-pipelines for an example config.

Travis-ci and Coverage Sites

The expected most common usecase is launching coverage via a CI service to upload to a site like codecov or coveralls. Given the built in support and ubiquity of travis-ci it seems prudent to document the required steps here for new users. To follow these steps you'll first need a travis-ci and a project setup for your coverage reporting site of choice.

We recommend taking the minimal rust .travis.yml, installing the libssl-dev dependency tarpaulin has and then running Tarpaulin with the version of rustc you require. Tarpaulin is installed in before_cache to allow it to be cached and prevent having to reinstall every Travis run. You can also replace cargo test with a verbose run of tarpaulin to see the test results as well as coverage output.

Tarpaulin is ran after success as there are still some unstable features which could cause coverage runs to fail. If you don't rely on any of these features you can alternatively replace cargo test with a call to cargo tarpaulin.

For codecov.io you'll need to export CODECOV_TOKEN are instructions on this in the settings of your codecov project.

language: rust
# tarpaulin has only been tested on bionic and trusty other distros may have issues
dist: bionic
            - libssl-dev
cache: cargo
  - stable
  - beta
  - nightly
    - rust: nightly

before_script: |
  if [[ "$TRAVIS_RUST_VERSION" == stable ]]; then
    cargo install cargo-tarpaulin

- cargo clean
- cargo build
- cargo test

after_success: |
  if [[ "$TRAVIS_RUST_VERSION" == stable ]]; then
    # Uncomment the following line for coveralls.io
    # cargo tarpaulin --ciserver travis-ci --coveralls $TRAVIS_JOB_ID

    # Uncomment the following two lines create and upload a report for codecov.io
    # cargo tarpaulin --out Xml
    # bash <(curl -s https://codecov.io/bash)

If you rely on certain nightly features you may need to change the before_script to before_cache to force tarpaulin to reinstall each time. However, if it can be avoided it will speed up your CI runs.

Alternatively, there are the prebuilt docker images or the travis-install shell script. The travis-install script will install the latest tagged release built on travis to your travis instance and significantly speeds up the travis builds. You can install via that script using bash <(curl https://raw.githubusercontent.com/xd009642/tarpaulin/master/travis-install.sh).

The prebuilt binary is built using github actions ubuntu:latest image, because of this it doesn't work on xenial or trusty, but it works on bionic. You should still keep the rest of the recommended travis settings.

GitHub Actions

File .github/workflows/coverage.yml Example how to run coverage within docker with seccomp in GitHub Actions and push the result to .

name:                           coverage

on:                             [push]
    name:                       coverage
    runs-on:                    ubuntu-latest
      image:                    xd009642/tarpaulin:develop-nightly
      options:                  --security-opt seccomp=unconfined
      - name:                   Checkout repository
        uses:                   actions/checkout@v2

      - name:                   Generate code coverage
        run: |
          cargo +nightly tarpaulin --verbose --all-features --workspace --timeout 120 --out Xml

      - name:                   Upload to codecov.io
        uses:                   codecov/codecov-action@v2
          # token:                ${{secrets.CODECOV_TOKEN}} # not required for public repos
          fail_ci_if_error:     true


To run tarpaulin on CircleCI you need to run tarpaulin in docker and set the machine flag to true as shown below:

    machine: true
      - checkout
      - run:
          name: Coverage with docker
          command: docker run --security-opt seccomp=unconfined -v "${PWD}:/volume" xd009642/tarpaulin

Gitlab Pipelines

To get the coverage results showing up in your Gitlab pipelines add the following regex to the Test coverage section in the gitlab job definition in .gitlab-ci.yml:

job: ...
  coverage: '/^\d+.\d+% coverage/'

Gitlab can show coverage information in the diff of a merge request. For that, use

job: ...
        coverage_format: cobertura
        path: cobertura.xml

and generate a cobertura.xml as described under Pycobertura.

For installation add cargo install cargo-tarpaulin -f to the script section.


Tarpaulin has builds deployed to docker-hub, to run Tarpaulin on any system that has Docker, run this in your project directory:

docker run --security-opt seccomp=unconfined -v "${PWD}:/volume" xd009642/tarpaulin

This builds your project inside Docker and runs Tarpaulin without any arguments. There are also tags available for the latest version on the develop branch in stable or nightly. And versions after 0.5.6 will have the latest release built with the rust stable and nightly compilers. To get the latest development version built with rustc-nightly run the following:

docker run --security-opt seccomp=unconfined -v "${PWD}:/volume" xd009642/tarpaulin:develop-nightly

Note that the build might fail if the Docker image doesn't contain any necessary dependencies. In that case, you can install dependencies before, like this:

docker run --security-opt seccomp=unconfined -v "${PWD}:/volume" xd009642/tarpaulin sh -c "apt-get install xxx && cargo tarpaulin"

Alternatively, taking the seccomp json and setting all seccomp actions for the personality syscall to SCMP_ACT_ALLOW to avoid removing all the seccomp policies for Docker.

Config file

Tarpaulin has a config file setting where multiple coverage setups can be encoded in a toml file. This can be provided by an argument or if a .tarpaulin.toml or tarpaulin.toml is present in the same directory as the projects manifest or in the root directory that will be used unless --ignore-config is passed. Below is an example file:

features = "feature_a"

features = "feature_a feature_b"
release = true

coveralls = "coveralls_key"
out = ["Html", "Xml"]

Here we'd create three configurations, one would run your tests with feature_a enabled, and the other with the tests built in release and both feature_a and feature_b enabled. The last configuration uses a reserved configuration name report and this doesn't result in a coverage run but affects the report output. This is a reserved feature name and any non-reporting based options chosen will have no effect on the output of tarpaulin.

For reference on available keys and their types refer to the CLI help text at the start of the readme or src/config/mod.rs for the concrete types if anything is unclear. For arguments to be passed into the test binary that follow -- in tarpaulin use args in the toml file.

Setting the field config will have no effect on the run as it won't be parsed for additional configuration.

For the flags --lib, --examples, --benches, --tests, --all-targets, --doc, --bins use the run-types entry in the config file.

Extending Tarpaulin

There are some tools available which can extend tarpaulin functionality for other potential user needs.

Procedural Macros

Normally, Tarpaulin can't report on code coverage within the code for a procedural macro. You'll need to add a test that expands the macro at run-time in order to get those stats. The runtime-macros crate was made for this purpose, and its documentation describes how to use it with Tarpaulin.


pycobertura is a python library for working with cobertura reports. It offers a report diffing tool as well as its own report implementations.

To generate a cobertura.xml simply run the following tarpaulin command:

cargo tarpaulin --out Xml

Then install pycobertura with pip and execute the desired command.

As tarpaulin doesn't allow you to change the name of the generated cobertura report be mindful of this if diffing reports between multiple commits.

Issues and Contributing

Issues, feature requests and pull requests are always welcome! For a guide on how to approach bugs found in Tarpaulin and adding features please check [CONTRIBUTING](CONTRIBUTING.md).

Rust 1.23 introduced a regression in the compiler affecting tarpaulin's accuracy. If you see missing lines or files, check your compiler version.


  • [ ] Branch coverage for tests
  • [ ] Condition coverage for tests
  • [ ] MCDC coverage reports
  • [ ] LLVM coverage support
  • [ ] Support for embedded targets
  • [ ] OSX support
  • [ ] Windows support


Tarpaulin is currently licensed under the terms of both the MIT license and the Apache License (Version 2.0). See LICENSE-MIT and LICENSE-APACHE for more details.

*Note that all licence references and agreements mentioned in the tarpaulin README section above are relevant to that project's source code only.