assert.verifySteps()

version added: 2.2

verifySteps( steps [, message ] )

A helper assertion to verify the order and number of steps in a test.

name description
steps (array) Array of strings representing steps to verify
message (string) A short description of the assertion

Description

The assert.verifySteps() assertion compares a given array of string values (representing steps) with the order and values of previous step() calls. This assertion is helpful for verifying the order and count of portions of code paths, especially asynchronous ones.

The list of steps to validate is reset when assert.verifySteps([/* ...snip ... */]) is called. This allows multiple combinations of assert.step and assert.verifySteps within the same test.

Examples

The following examples look at scenarios in which the Step API is particularly useful and shows how you might have implemented the same functionality with less-specific APIs.

Verifying Hook Execution Order

Without Step API

QUnit.test( "user-defined hooks execute in correct order", function( assert ) {
  let lastStep = 'none';
  let startCount = 0;
  let middleCount = 0;
  let endCount = 0;

  obj.start = function() {
    assert.equal(lastStep, 'none');
    lastStep = 'start';
    startCount++;
  };
  obj.middle = function() {
    assert.equal(lastStep, 'start');
    lastStep = 'middle';
    middleCount++;
  };
  obj.end = function() {
    assert.equal(lastStep, 'middle');
    endCount++;
  };

  return obj.process().then(function() {
    assert.equal(startCount, 1);
    assert.equal(middleCount, 1);
    assert.equal(endCount, 1);
  });
});

With Step API

QUnit.test( "user-defined hooks execute in correct order", function( assert ) {
  obj.start = function() {
    assert.step('start');
  };
  obj.middle = function() {
    assert.step('middle');
  };
  obj.end = function() {
    assert.step('end');
  };

  return obj.process().then(function() {
    assert.verifySteps(['start', 'middle', 'end']);
  });
});

Verifying Evented Systems

Without Step API

QUnit.test( "subscribe/unsubscribe", function( assert ) {

  const publisher = new Publisher();
  const messages = [];

  const subscriber1 = message => messages.push(`Subscriber #1: ${message}`);
  const subscriber2 = message => messages.push(`Subscriber #2: ${message}`);

  publisher.subscribe(subscriber1);
  publisher.subscribe(subscriber2);

  publisher.publish('Hello!');

  publisher.unsubscribe(subscriber1);

  publisher.publish('World!');

  assert.deepEqual(messages, [
    'Subscriber #1: Hello!',
    'Subscriber #2: Hello!',
    'Subscriber #2: World!'
  ]);
});

With Step API

QUnit.test( "subscribe/unsubscribe", function( assert ) {

  const publisher = new Publisher();

  const subscriber1 = message => assert.step(`Subscriber #1: ${message}`);
  const subscriber2 = message => assert.step(`Subscriber #2: ${message}`);

  publisher.subscribe(subscriber1);
  publisher.subscribe(subscriber2);

  publisher.publish('Hello!');

  publisher.unsubscribe(subscriber1);

  publisher.publish('World!');

  assert.verifySteps([
    'Subscriber #1: Hello!',
    'Subscriber #2: Hello!',
    'Subscriber #2: World!'
  ]);
});

Verifying Steps Multiple Times

QUnit.test( "verify steps", function test(assert){
    assert.expect( 5 );

    assert.step( "do stuff 1" );
    assert.step( "do stuff 2" );
    assert.verifySteps( [ "do stuff 1", "do stuff 2" ] );

    assert.step( "do stuff 3" );
    assert.verifySteps( [ "do stuff 3" ] );
} );