Filter expressions

Nextest supports a domain-specific language (DSL) for filtering tests. The DSL is inspired by, and is similar to, Bazel query and Mercurial revsets.

Example: Running all tests in a crate and its dependencies

To run all tests in my-crate and its dependencies, run:

cargo nextest run -E 'deps(my-crate)'

The argument passed into the -E command-line option is called a filter expression. The rest of this page describes the full syntax for the expression DSL.

The filter expression DSL

A filter expression defines a set of tests. A test will be run if it matches a filter expression.

On the command line, multiple filter expressions can be passed in. A test will be run if it matches any of these expressions. For example, to run tests whose names contain the string my_test as well as all tests in package my-crate, run:

cargo nextest run -E 'test(my_test)' -E 'package(my-crate)'

This is equivalent to:

cargo nextest run -E 'test(my_test) + package(my-crate)'

Examples

  • package(serde) and test(deserialize): every test containing the string deserialize in the package serde
  • not (test(/parse[0-9]*/) | test(run)): every test name not matching the regex parse[0-9]* or the substring run

Note: If you pass in both a filter expression and a standard, substring-based filter, tests must match both filter expressions and substring-based filters.

For example, the command:

cargo nextest run -E 'package(foo)' test_bar test_baz

will run all tests that are both in package foo and match test_bar or test_baz.

DSL reference

This section contains the full set of operators supported by the DSL.

Basic predicates

  • all(): include all tests.
  • test(name-matcher): include all tests matching name-matcher.
  • package(name-matcher): include all tests in packages (crates) matching name-matcher.
  • deps(name-matcher): include all tests in crates matching name-matcher, and all of their (possibly transitive) dependencies.
  • rdeps(name-matcher): include all tests in crates matching name-matcher, and all the crates that (possibly transitively) depend on name-matcher.
  • kind(name-matcher): include all tests in binary kinds matching name-matcher. Binary kinds include:
    • lib for unit tests, typically in the src/ directory
    • test for integration tests, typically in the tests/ directory
    • bench for benchmark tests
    • bin for tests within [[bin]] targets
    • proc-macro for tests in the src/ directory of a procedural macro
  • binary(name-matcher): include all tests in binary names matching name-matcher.
    • For tests of kind lib and proc-macro, the binary name is the same as the name of the crate.
    • Otherwise, it's the name of the integration tests, benchmark, or binary target.
  • platform(host) or platform(target): include all tests that are built for the host or target platform, respectively.
  • none(): include no tests.

Note: If a filter expression always excludes a particular binary, it will not be run, even to get the list of tests within it. This means that a command like:

cargo nextest list -E 'platform(host)'

will not execute any test binaries built for the target platform. This is generally what you want, but if you would like to list tests anyway, include a test() predicate. For example, to list test binaries for the target platform (using, for example, a target runner), but skip running them:

cargo nextest list -E 'platform(host) + not test(/.*/)' --verbose

Name matchers

  • ~string: match a package or test name containing string
  • =string: match a package or test name that's equal to string
  • /regex/: match a package or test name if any part of it matches the regular expression regex. To match the entire string against a regular expression, use /^regex$/. The implementation uses the regex crate.
  • string: default matching strategy.
    • For tests (test()), this is equivalent to ~string.
    • For packages (package(), deps() and rdeps()), binary kinds (kind()), and , this is equivalent to =string.

If you're constructing an expression string programmatically, it is recommended that you always use a prefix to avoid ambiguity.

Escape sequences

The ~string and =string name matchers can contain escape sequences, preceded by a backslash (\).

  • \n: line feed
  • \r: carriage return
  • \t: tab
  • \\: backslash
  • \/: forward slash
  • \): closing parenthesis
  • \,: comma
  • \u{7FFF}: 24-bit Unicode character code (up to 6 hex digits)

All other escape sequences are invalid.

The regular expression matcher supports the same escape sequences that the regex crate does. This includes character classes like \d. Additionally, \/ is interpreted as an escaped /.

Operators

  • set_1 & set_2, set_1 and set_2: the intersection of set_1 and set_2
  • set_1 | set_2, set_1 + set_2, set_1 or set_2: the union of set_1 or set_2
  • not set, !set: include everything not included in set
  • set_1 - set_2: equivalent to set_1 and not set_2
  • (set): include everything in set

Operator precedence

In order from highest to lowest, or in other words from tightest to loosest binding:

  1. ()
  2. not, !
  3. and, &, -
  4. or, |, +

Within a precedence group, operators bind from left to right.

Examples
  • test(a) & test(b) | test(c) is equivalent to (test(a) & test(b)) | test(c).
  • test(a) | test(b) & test(c) is equivalent to test(a) | (test(b) & test(c)).
  • test(a) & test(b) - test(c) is equivalent to (test(a) & test(b)) - test(c).
  • not test(a) | test(b) is equivalent to (not test(a)) | test(b).