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cargo-test(1)

NAME

cargo-test --- Execute unit and integration tests of a package

SYNOPSIS

cargo test [options] [testname] [-- test-options]

DESCRIPTION

Compile and execute unit, integration, and documentation tests.

The test filtering argument TESTNAME and all the arguments following the two dashes (--) are passed to the test binaries and thus to libtest (rustc's built in unit-test and micro-benchmarking framework). If you're passing arguments to both Cargo and the binary, the ones after -- go to the binary, the ones before go to Cargo. For details about libtest's arguments see the output of cargo test -- --help and check out the rustc book's chapter on how tests work at https://doc.rust-lang.org/rustc/tests/index.html.

As an example, this will filter for tests with foo in their name and run them on 3 threads in parallel:

cargo test foo -- --test-threads 3

Tests are built with the --test option to rustc which creates a special executable by linking your code with libtest. The executable automatically runs all functions annotated with the #[test] attribute in multiple threads. #[bench] annotated functions will also be run with one iteration to verify that they are functional.

If the package contains multiple test targets, each target compiles to a special executable as aforementioned, and then is run serially.

The libtest harness may be disabled by setting harness = false in the target manifest settings, in which case your code will need to provide its own main function to handle running tests.

Documentation tests

Documentation tests are also run by default, which is handled by rustdoc. It extracts code samples from documentation comments of the library target, and then executes them.

Different from normal test targets, each code block compiles to a doctest executable on the fly with rustc. These executables run in parallel in separate processes. The compilation of a code block is in fact a part of test function controlled by libtest, so some options such as --jobs might not take effect. Note that this execution model of doctests is not guaranteed and may change in the future; beware of depending on it.

See the rustdoc book for more information on writing doc tests.

Working directory of tests

The working directory when running each unit and integration test is set to the root directory of the package the test belongs to. Setting the working directory of tests to the package's root directory makes it possible for tests to reliably access the package's files using relative paths, regardless from where cargo test was executed from.

For documentation tests, the working directory when invoking rustdoc is set to the workspace root directory, and is also the directory rustdoc uses as the compilation directory of each documentation test. The working directory when running each documentation test is set to the root directory of the package the test belongs to, and is controlled via rustdoc's --test-run-directory option.

OPTIONS

Test Options

Target Selection

When no target selection options are given, cargo test will build the following targets of the selected packages:

lib --- used to link with binaries, examples, integration tests, and doc tests
bins (only if integration tests are built and required features are available)
examples --- to ensure they compile
lib as a unit test
bins as unit tests
integration tests
doc tests for the lib target

The default behavior can be changed by setting the test flag for the target in the manifest settings. Setting examples to test = true will build and run the example as a test, replacing the example's main function with the libtest harness. If you don't want the main function replaced, also include harness = false, in which case the example will be built and executed as-is.

Setting targets to test = false will stop them from being tested by default. Target selection options that take a target by name (such as --example foo) ignore the test flag and will always test the given target.

Doc tests for libraries may be disabled by setting doctest = false for the library in the manifest.

See Configuring a target for more information on per-target settings.

{{#option "--doc" }} Test only the library's documentation. This cannot be mixed with other target options. {{/option}}

Compilation Options

Output Options

Display Options

By default the Rust test harness hides output from test execution to keep results readable. Test output can be recovered (e.g., for debugging) by passing --nocapture to the test binaries:

cargo test -- --nocapture

Manifest Options

Miscellaneous Options

The --jobs argument affects the building of the test executable but does not affect how many threads are used when running the tests. The Rust test harness includes an option to control the number of threads used:

cargo test -j 2 -- --test-threads=2

While cargo test involves compilation, it does not provide a --keep-going flag. Use --no-fail-fast to run as many tests as possible without stopping at the first failure. To "compile" as many tests as possible, use --tests to build test binaries separately. For example:

cargo build --tests --keep-going
cargo test --tests --no-fail-fast

EXAMPLES

Execute all the unit and integration tests of the current package:
```
cargo test
```
Run only tests whose names match against a filter string:
```
cargo test name_filter
```
Run only a specific test within a specific integration test:
```
cargo test --test int_test_name -- modname::test_name
```

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