jest-gwt

A small library to help Jest support given-when-then style testing without a bunch of overhead

Compatibility Chart

jest-gwt Version	Jest Version
1.x	24.x, 25.x
2.x	26.x, 27.x
3.x	> 26.x

Usage

1. Install the package

   npm i --save-dev jest-gwt

2. In your test files, import test

   import test from 'jest-gwt';

3. Write a test!

   describe('test context', () => {
     test('has no expected errors', {
       given: {
         mock_jest_test_function,
         GOOD_test_case,
       },
       when: {
         executing_test_case,
       },
       then: {
         all_GIVENS_called,
         all_WHENS_called,
         all_THENS_called,
       },
     });
   });

Scenario Test

Sometimes a GWT flow doesn't make sense. You might be writing integration tests. Or something that needs to assert something, then do another thing, then assert something else.

In these cases, you can use the scenario definition style which allows chaining when and then, followed by then_when and then blocks.

{
  given: {
    mock_jest_test_function,
    GOOD_test_case,
  },
  scenario: [{
    when: {
      executing_test_case,
    },
    then: {
      assert_something,
    },
  }, {
    then_when: {
      user_submits_form,
    },
    then: {
      something_else_happens,
      yet_another_thing_is_true,
    },
  }, {
    then_when: {
      something_happens,
    },
    then: {
      expect_error: some_check,
      and: {
        something_is_still_true,
      },
    }
  }]
}

Disabling a test

Sometimes you want a test to be disabled in code. Jest offers this functionality with the xtest method, and we've duplicated this logic, but with strong typing so you can disable your gwt style tests.

import test, { xtest } from 'jest-gwt';

describe('test context', () => {
  test('this test will run', {
    then: {
      CANARY,
    },
  });

  xtest('this test will NOT run', {
    when: {
      oops_we_broke_this,
    },
  });
});

withAspect

withAspect wraps up jest's beforeEach and afterEach to allow preparing and cleaning up the context before running tests.

withAspect(
  // this is the beforeEach. Do your prep work here
  function(this: Context) {
  },
  // this is the afterEach. It is OPTIONAL. If you need to do clean up of
  // external resources you allocated in the beforeEach, do it here
  function(this: Context) {
  }
)

The afterEach has access to whatever values you put on the Context in the beforeEach. It does NOT have access to the values put on the Context during the specific test.

Detailed Usage

Please refer to gwt-runner for detailed usage on how to write tests and clauses.