4. Fant


Fantom includes a unit test framework baked right into the runtime - it is very similar to common test frameworks such as JUnit. The key concepts for testing:

  • Write test classes which subclass Test
  • Write test methods which start with "test"
  • Assert test conditions via the "verifyXXX" methods
  • Run the tests the fant command line tool

Organizing Tests

By convention test classes are organized directly within their associated pod using the following directory structure:


Writing Tests

Any concrete class within a pod which extends from Test is considered a test class. Any method which starts with "test" in a test class is considered a test method. Test methods must be public instance methods with no parameters. Test methods assert conditions using the verify methods. Three of the most commonly used verify methods:

  • verify: assert a boolean condition is true
  • verifyEq: assert two objects are equal
  • verifyErr: assert an exception is thrown

Here is an example of a test class:

class SampleTest : Test
  Void testStuff()
    verifyEq('A'.lower, 'a')
    verifyErr(ParseErr#) { x := Int.fromStr("@#!") }

Running Tests

The fant launcher is used to run tests. You can pass a pod name, type qname, or slot qname to run any test in any installed pod. You can also pass "-all" to run all tests in all pods:

fant -all
fant testSys
fant testSys::StrTest
fant testSys::StrTest.testEach

You can also pass a script filename to fant:

fant /tests/foo.fan

The script will be compiled into a pod and then all subclasses of Test will be run.

The test results will be printed to standard out. Any test failures will be raised as exceptions.

Test Lifecycle

When running tests, each test method is executed as follows:

  1. A fresh instance of the test class is instantiated via make
  2. Test.setup is called
  3. The test method is called with no arguments
  4. Any exceptions raised are trapped and the test is marked failed
  5. Test.teardown is guaranteed to be called

Any exception raised by the test method is considered a failure. Calls to verify which fail will just raise an exception.