#cargo #cargo-subcommand #testing

bin+lib cargo-tarpaulin

Cargo-Tarpaulin is a tool to determine code coverage achieved via tests

60 releases

✓ Uses Rust 2018 edition

0.11.1 Mar 13, 2020
0.10.2 Jan 15, 2020
0.10.0 Dec 7, 2019
0.9.3 Nov 20, 2019
0.3.9 Jul 24, 2017

#9 in Cargo plugins

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4,742 downloads per month
Used in runtime-macros

MIT/Apache and MPL-2.0+



Build Status Latest Version License:MIT Docker Developers Wiki

Tarpaulin is designed to be 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 but is still in the early development stage and therefore may contain some bugs. A lot of work has been done to get it working on some example projects and smaller crates so please report anything you find that's wrong. Also, check out our roadmap for planned features.

Tarpaulin only supports x86_64 processors running Linux. This is because instrumenting breakpoints into executables and tracing their execution requires processor and OS specific code. It is a goal when greater stability is reached to add wider system support, however this is sufficient to run Tarpaulin on popular CI tools like Travis.

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: 0.10.2
Tool to analyse test coverage of cargo projects

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

        --all                    Alias for --workspace (deprecated)
        --all-features           Build all available features
    -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
        --force-clean            Adds a clean stage to work around cargo bugs that may affect coverage results
    -f, --forward                Forwards unexpected signals to test. Tarpaulin will still take signals it is expecting.
        --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
    -i, --ignored                Run ignored tests as well
    -l, --line                   Line coverage
        --locked                 Do not update Cargo.lock
        --no-default-features    Do not include default features
        --no-run                 Compile tests but don't run coverage
        --offline                Run without accessing the network
        --release                Build in release mode.
    -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
        --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.
        --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
    -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
        --features <FEATURE>...      Features to be included in the target project
        --manifest-path <PATH>       Path to Cargo.toml
    -o, --out <FMT>...               Output format of coverage report [possible values: Json, Toml, Stdout, Xml, Html,
        --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
        --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]
        --target-dir <DIR>           Directory for all generated artifacts
    -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


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
  • 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 depends on cargo which depends on SSL. Make sure you've installed your distros SSL development libraries and they are on your path before attempting to install tarpaulin. For example for Debian/Ubuntu:

apt-get update && apt-get install libssl-dev pkg-config cmake zlib1g-dev

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

cargo install cargo-tarpaulin

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.

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

#[cfg_attr(tarpaulin, skip)]
fn main() {
    println!("I won't be included in results");

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 Jenkin's 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
sudo: required # required for some configurations
# 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.


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 parsing section in the pipelines settings.

^\d+.\d+% coverage

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"

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 argumnet 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_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 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.

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 it's 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.

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


  • Line coverage for tests
  • Branch coverage for tests
  • Condition coverage for tests
  • Annotated coverage reports
  • Coverage reports in the style of existing tools (i.e. kcov)
  • Integration with 3rd party tools like coveralls or codecov
  • Optional coverage statistics for doctests (nightly only tracking issue)
  • MCDC coverage reports
  • 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.


I wouldn't have been able to make progress as quickly in this project without Joseph Kain's blog on writing a debugger in Rust and C. It's a great read, so I recommend you check it out here.


~874K SLoC