mops test

Mops can run Motoko unit tests

mops test

Put your tests in test/*.test.mo files.

All tests run as quickly as possible thanks to parallel execution.

See test package to help you write tests.

Options

--reporter, -r

Test reporter.

--reporter <reporter>

Available reporters:

• verbose - print each file/suite/test name and Debug.print output
• files - print only test files
• compact - pretty progress bar
• silent - print only errors

Default verbose.

note

Only verbose reporter prints Debug.print output.

--watch, -w

Re-run tests every time you change *.mo files.

--watch

--mode

Test run mode

--mode <mode>

Available modes:

• interpreter - run tests via moc -r (default)
• wasi - compile test file to wasm and execute it with wasmtime. Useful, when you use to_candid/from_candid, or if you get stackoverflow errors.

You can also specify wasi mode for a specific test file by adding the line below as the first line in the test file

// @testmode wasi

--verbose

Show replica logs

-- <moc flags>

Pass extra flags directly to the Motoko compiler for this invocation. Appended after [moc].args from mops.toml.

mops test -- -Werror

--locked

Require an up-to-date mops.lock and never write it — fails if the lockfile is missing or no longer matches mops.toml and the registry. Intended for CI, so that a job can run this command without a preceding mops install. See mops install --locked.

Replica tests

Replica tests are useful if you need to test actor code which relies on the IC API(cycles, timers, canister upgrades, etc.).

To run replica tests, your test file should look like this:

...

actor {
  public func runTests() : async () {
    // your tests here
  };
};

Example:

import {test} "mo:test/async";
import MyCanister "../my-canister";

actor {
  // add cycles to deploy your canister
  ExperimentalCycles.add<system>(1_000_000_000_000);

  // deploy your canister
  let myCanister = await MyCanister.MyCanister();

  public func runTests() : async () {
    await test("test name", func() : async () {
      let res = await myCanister.myFunc();
      assert res == 123;
    });
  };
};

Make sure your actor doesn't have a name actor {.

Make sure your actor has runTests method.

See example here.

Replica tests run on PocketIC, which Mops downloads and manages itself — dfx is not involved and does not need to be installed. Pin a version with mops toolchain use pocket-ic <version>; with no pin, Mops uses the default version it ships with. See supported versions.

Under the hood, Mops will:

• Start a PocketIC server on an ephemeral port
• Compile test files and deploy them
• Call runTests method of the deployed canister