Expand description

datatest-stable is a very simple test harness intended to write data-driven tests, where individual test cases are specified as files and not as code. Given:

  • a test my_test that accepts a path as input
  • a directory to look for files in
  • a pattern to match files on

datatest-stable will call the my_test function once per matching file in the directory.

datatest-stable works with cargo nextest, and is part of the nextest-rs organization on GitHub.


  1. Configure the test target by setting harness = false in Cargo.toml:
name = "<test target name>"
harness = false
  1. Call the datatest_stable::harness!(testfn, root, pattern) macro with the following parameters:
  • testfn - The test function to be executed on each matching input. This function must have the type fn(&Path) -> datatest_stable::Result<()>
  • root - The path to the root directory where the input files (fixtures) live. This path is relative to the root of the crate.
  • pattern - the regex used to match against and select each file to be tested.

The three parameters can be repeated if you have multiple sets of data-driven tests to be run: datatest_stable::harness!(testfn1, root1, pattern1, testfn2, root2, pattern2)


This is an example test. Use it with harness = false.

use std::path::Path;

fn my_test(path: &Path) -> datatest_stable::Result<()> {
    // ... write test here


datatest_stable::harness!(my_test, "path/to/fixtures", r"^.*/*");

Minimum supported Rust version (MSRV)

The minimum supported Rust version is Rust 1.56. MSRV bumps may be accompanied by a minor version update; at any time, at least the last 3 stable versions of Rust will be supported.

See also


datatest-stable test harness entry point. Should be declared in the test module.

Type Definitions

The result type for datatest-stable tests.