expect.md

layout	title	excerpt	groups	redirect_from	version_added
page-api	assert.expect()	Specify how many assertions are expected in a test.	assert	/assert/expect/ /expect/	1.0.0

expect( amount )

Specify how many assertions are expected in a test.

name	description
amount	Number of expected assertions in this test

This is most commonly used as assert.expect(0), which indicates that a test may pass without making any assertions. This means the test is only used to verify that the code runs to completion, without any uncaught errors. This is is essentially the inverse of assert.throws().

This can also be used to explicitly require a certain number of assertions to be recorded in a given test. If afterwards the number of assertions does not match the expected count, the test will fail.

It is recommended to test asynchronous code with assert.step() or assert.async() instead.

Examples

Example: No assertions

A test without any assertions:

QUnit.test('example', function (assert) {
  assert.expect(0);

  var android = new Robot();
  android.up(2);
  android.down(2);
  android.left();
  android.right();
  android.left();
  android.right();
  android.attack();
  android.jump();
});

Example: Custom assert

If you use a generic assertion library that throws when an expectation is not met, you can use assert.expect(0) if there are no other assertions needed in the test.

QUnit.test('example', function (assert) {
  assert.expect(0);

  var android = new Robot(database);
  android.run();

  database.assertNoOpenConnections();
});

Example: Explicit count

Require an explicit assertion count.

QUnit.test('example', function (assert) {
  assert.expect(2);

  function calc (x, operation) {
    return operation(x);
  }

  let result = calc(2, function (x) {
    assert.true(true, 'calc() calls operation function');
    return x * x;
  });

  assert.strictEqual(result, 4, '2 squared equals 4');
});