to match

• <string> to match <regexp>

Asserts a string matches a regular expression.

expect('Hello beautiful world!', 'to match', /bea.t.*/);

In case of a failing expectation you get the following output:

expect('Hello world!', 'to match', /beautiful/);

expected 'Hello world!' to match /beautiful/

This assertion can be negated using the not flag:

expect('Hello world!', 'not to match', /beautiful/);

In case of a failing expectation you get the following output:

expect('Hello beautiful world!', 'not to match', /beautiful/);

expected 'Hello beautiful world!' not to match /beautiful/
 
Hello beautiful world!

The return value of String.prototype.match will be provided as the fulfillment value of the returned promise, so the values captured by the regular expression are available to the then function:

return expect('Hello world!', 'to match', /(\w+)!/).then(function (captures) {
  expect(captures[0], 'to equal', 'world!');
  expect(captures[1], 'to equal', 'world');
  expect(captures.index, 'to equal', 6);
});

Or using the Bluebird-specific .spread extension:

return expect('Hello world!', 'to match', /(\w+)!/).spread(function ($0, $1) {
  expect($0, 'to equal', 'world!');
  expect($1, 'to equal', 'world');
});