Examples of ways to trigger SequelizeJS exceptions so you can more easily test the .catch() branches of query promise chains.

test-sequelize-failures.js

// This mechanism assumes you have an api.models hash of models - adjust to suit your actual location.
api.utils.recursiveDirectoryGlob(__dirname + '/../models', 'js').forEach(function(filename) {
    var modelName = (filename.replace(/\\/g, '/').split('/')).pop().replace('.js', '');

    console.log('ORM: Loading model ' + modelName);
    models[modelName] = sequelize.import(filename);
});

// Pretend we've had a database failure when creating roles
Object.keys(api.models).map(function(modelName) {
    api.models[modelName].shouldFail = false;
    api.models[modelName].beforeCreate(function(instance, options, callback) {
        if (api.models[modelName].shouldFail) {
            callback('Unable to process request.');
        } else {
            callback();
        }
    });

    api.models[modelName].beforeBulkCreate(function(instance, options, callback) {
        if (api.models[modelName].shouldFail) {
            callback('Unable to process request.');
        } else {
            callback();
        }
    });

    api.models[modelName].beforeFind(function(options, callback) {
        if (api.models[modelName].shouldFail) {
            callback('Unable to process request.');
        } else {
            callback();
        }
    });
});

// Example usage: Failing a request to a user object
describe('Action: getUser', function() {
    // ... Other tests here ...

    it('should handle query failures cleanly', function(done) {
        api.models.user.shouldFail = true;
        api.models.user.findOne(1).then(function(response) {
            throw new Error('Query failure test did not throw an exception');
        }).catch(function(e) {
            assert.that(e, is.not.null());
        });
    });
});