Except for user management methods like createUser
that validate their arguments, MockFirebase calls will never results in asynchronous errors since all data is maintained locally. Instead, MockFirebase gives you two options for testing error handling behavior for both data and authentication methods:
failNext(method, err)
: specifies that the next invocation ofmethod
should call its completion callback witherr
forceCancel(err [, event] [, callback] [, context]
): cancels all data event listeners registered withon
that match the provided arguments
While failNext
is limited to specifying a single error per method, forceCancel
can simulate the cancellation of any number of event listeners.
Using failNext
is a simple way to test behavior that handles write errors or read errors that occur immediately (e.g. an attempt to read a path a user is not authorized to view).
var log = {
error: function (err) {
console.error(err);
}
};
var people = {
ref: function () {
return new Firebase('htttps://example.firebaseio.com/people')
},
create: function (person) {
people.ref().push(person, function (err) {
if (err) log.error(err);
});
}
};
In our tests, we'll override log.error
to ensure that it's properly called.
MockFirebase.override();
var ref = people.ref();
var errors = [];
log.error = function (err) {
errors.push(err);
};
people.failNext('push');
people.create({
first: 'Ben'
});
people.flush();
console.assert(errors.length === 1, 'people.create error logged');
forceCancel
simulates more complex errors that involve a set of event listeners on a path. forceCancel
allows you to simulate Firebase API behavior that would normally occur in rare cases when a user lost access to a particular reference. For a simple read error, you could use failNext('on', err)
instead.
In this example, we'll also record an error when we lose authentication on a path.
people.ref().on('child_added', function onChildAdded (snapshot) {
console.log(snapshot.val().first);
}, function onCancel () {
log.error(err);
});
var errors = [];
log.error = function (err) {
errors.push(err);
};
var err = new Error();
people.forceCancel(err, 'child_added');
console.assert(errors.length === 1, 'child_added was cancelled');