to be observable

Passes if the subject is a Knockout observable.

expect(ko.observable(42), 'to be observable');

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

expect(42, 'to be observable');

expected 42 to be observable

This assertion can be negated using the not flag:

expect(42, 'not to be observable');

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

expect(ko.observable(42), 'not to be observable');

expected ko.observable(42) not to be observable