Testing your Package

Mason provides the functionality to test packages through the mason test subcommand. There are two styles of writing mason tests:

  1. Tests that utilize the UnitTest module to determine pass/fail status

  2. Tests that rely on the exit code to determine pass/fail status

Here is an example of a UnitTest-based test:

use UnitTest;

config const testParam: bool = true;

proc myTest(test: borrowed Test) throws{


Mason testing that uses UnitTest will treat each individual function as a test, and the test will be considered successful if no assertions failed and no halts were reached within the function body.

See the UnitTest documentation to learn more about writing unit tests in Chapel.

Here is an example of an exit-code-based tests:

config const testParam: bool = true;

if testParam {
  writeln("Test Passed!");
else {

Mason testing that relies on exit code tests each file as a test, and the test will be considered successful if the program compiled and exited with an exit code of 0.

These tests should be configured such that a failure produces an exit code other than 0. Returning a non-zero exit code can be accomplished by calling exit() or throwing an uncaught error.

Both exit-code and UnitTest style tests can be used within a single mason package.

After adding our test, the package structure will be as follows:

 ├── Mason.lock
 ├── Mason.toml
 ├── example/
 ├── src/
 │   └── myPackage.chpl
 ├── target/
 │   ├── debug/
 │   │   └── myPackage/
 │   ├── example/
 │   ├── release/
 │   │   └── myPackage
 │   └── test/
 └── test/
      └── myPackageTest.chpl

Use mason test to run the test(s). If tests are not explicitly specified in Mason.toml, Mason will gather all the tests found in test/, compile them with the dependencies listed in your Mason.toml and run them producing the following output:

--- Results ---
Test: myPackageTest Passed

--- Summary:  1 tests run ---
-----> 1 Passed
-----> 0 Failed

Specific tests can be run by listing their names or substrings of their names as command line arguments:

# Run these specific tests:
mason test test/test1.chpl test/test2.chpl
# Run any test file with 'test1' or 'test2' in the name
mason test test1 test2
# Run any test file with the '1' in the name
mason test 1

Specifying tests to run in the command line ignores the list of tests in Mason.toml, and searches all files in test/.

Additional output can be displayed by throwing the --show flag.


mason test can also be used outside of a mason package as a UnitTest test runner. See UnitTest for more information.

Tests can be listed in the Mason.toml as a TOML array of strings for the tests field:

chplVersion = "1.18.0"
license = "None"
name = "myPackage"
tests = ["test1.chpl",
version = "0.1.0"

A user may also set the CHPL_COMM value for running the tests, e.g. none, gasnet, ugni using mason test --setComm.