Sinon mocking with Sequelize - node.js

Question

I have the following nodejs function using Sequelize:
var processDatabase = function (dbConnection, schema, recordsets) {
var myLogTable = dbConnection.define(schema.tableName, schema.myLogSchema, schema.myLogSchemaIndex);
myLogTable.sync({
force: false,
freezeTableName: true,
logging: console.log
}).then(function () {
console.log('Table synced...');
for (k = 0; k < recordsets.length; k++) {
var query = "Some query";
dbConnection.query(
query, {
type: dbConnection.QueryTypes.SELECT
}
)
.then(function (results) {
console.log('MYSQL Selection Done');
})
.catch(function (err) {
console.log('MYSQL Error: ' + err.message);
});
}
}).catch(function (err) {
console.log('MYSQL Sync Error: ' + err.message);
});
};
I am new to mocking and do not especially know how to test the catch part.
This is my unit test which I can come up with, but I do not know how a call to sync can go to the catch part:
describe('when call processDatabase', function () {
it('should process successfully when sync fails', function (done) {
seqConnection.define = function (tableName, schema, schemaIndex) {
return mockMyLogModel;
};
processProfilesNotMapped(seqConnection, {
tableName: 'SomeTable',
myLogSchema: myLogSchema,
myLogSchemaIndex: myLogSchemaIndex
}, []);
done();
})
});
How would I write my mocking so that I can test both catch and also then so that they can be covered?

Answer 1

You need to defer an exception in your mock, since "sync" is using promises. You can use q library or any other. This way when you execute the sync function it will go to the catch section
Example using q:
describe('when call processDatabase', function () {
it('should process successfully when sync fails', function (done) {
seqConnection.define = function (tableName, schema, schemaIndex) {
const mock = {
sync: function(){
const deferred = q.defer();
deferred.reject(new Error('Some error'));
return deferred.promise;
}
}
return mock;
};
expect(
function(){
cmdManager.execute("getProfileDummy","hosar#gmail.com")
}
).to.throw(Error);
processProfilesNotMapped(seqConnection, {
tableName: 'SomeTable',
myLogSchema: myLogSchema,
myLogSchemaIndex: myLogSchemaIndex
}, []);
done();
})
});