I have an rspec test of a method that inserts or returns the first record if a record with given attributes doesn't exist. It looks like this
context "user doesn't exist" do
subject { User.find_or_create(name: "Jonh", login: "john") }
it { should be_an_instance_of(User) }
//and here I want to test that new user was inserted into database...
end
but I can't figure out how to use expect to change in this.
The way I usually test for this is by looking for the count of those objects to change:
it "creates a new user object" do
expect {
User.find_or_create(name: "John", login: "john")
}.to change{User.count}.by(1)
end
Admittedly, it doesn't fit that well with the subject pattern you've started with, but it's a necessary evil when you're testing that a certain method causes a change in the state of the system, rather than testing that objects have certain properties.
Related
Overview
I'm using Ember data and have a JSONAPI. Everything works fine until I have a more complex object (let's say an invoice for a generic concept) with an array of items called lineEntries. The line entries are not mapped directly to a table so need to be stored as raw JSON object data. The line entry model also contains default and computed values. I wish to store the list data as a JSON object and then when loaded back from the store that I can manipulate it as normal in Ember as an array of my model.
What I've tried
I've looked at and tried several approaches, the best appear to be (open to suggestions here!):
Fragments
Replace problem models with fragments
I've tried making the line entry model a fragment and then referencing the fragment on the invoice model as a fragmentArray. Line entries add to the array as normal but default values don't work (should they?). It creates the object and I can store it in the backend but when I return it, it fails with either a normalisation issue or a serialiser issue. Can anyone state the format the data be returned in? It's confusing as normalising the data seems to require JSONAPI but the fragment requires JSON serialiser. I've tried several combinations but no luck so far. My line entries don't have actual ids as the data is saved and loaded as a block. Is this an issue?
DS.EmbeddedRecordsMixin
Although not supported in JSONAPI, it sounds possible to use JSONAPI and then switch to JSONSerializer or RESTSerializer for the problem models. If this is possible could someone give me a working example and the JSON format that should be returned by the API? I have header authorisation and other such data so would I still be able to set this at the application level for all request not using my JSONAPI?
Ember-data-save-relationships
I found an add on here that provides an add on to do this. It seems more involved than the other approaches but when I've tried this I can send the data up by setting a the data as embedded. Great! But although it saves it doesn't unwrap it correct and I'm back with the same issues.
Custom serialiser
Replace the models serialiser with something that takes the data and sends it as plain JSON data and then deserialises back into something Ember can use. This sounds similar to the above but I do the heavy lifting. The only reason to do this is because all examples for the above solutions are quite light and don't really show how to set this up with an actual JSONAPI set up that would need it.
Where I am and what I need
Basically all approaches lead to saving the JSON fine but the return JSON from the server not being the correct format or the deserialisation failing but it's unclear what it should be or what needs to change without breaking the existing JSONAPI models that work fine.
If anyone know the format for return API data it may resolve this. I've tried JSONAPI with lineEntries returning the same format as it saved. I've tried placing relationship sections like the add on suggested and I've also tried placing relationship only data against the entries and an include section with all the references. Any help on this would be great as I've learned a lot through this but deadlines a looming and I can't see a viable solution that doesn't break as much as it fixes.
If you are looking for return format for relational data from the API server you need to make sure of the following:
Make sure the relationship is defined in the ember model
Return all successes with a status code of 200
From there you need to make sure you return relational data correctly. If you've set the ember model for the relationship to {async: true} you need only return the id of the relational model - which should also be defined in ember. If you do not set {async: true}, ember expects all relational data to be included.
return data with relationships in JSON API specification
Example:
models\unicorn.js in ember:
import DS from 'ember-data';
export default DS.Model.extend({
user: DS.belongsTo('user', {async: true}),
staticrace: DS.belongsTo('staticrace',{async: true}),
unicornName: DS.attr('string'),
unicornLevel: DS.attr('number'),
experience: DS.attr('number'),
hatchesAt: DS.attr('number'),
isHatched: DS.attr('boolean'),
raceEndsAt: DS.attr('number'),
isRacing: DS.attr('boolean'),
});
in routes\unicorns.js on the api server on GET/:id:
var jsonObject = {
"data": {
"type": "unicorn",
"id": unicorn.dataValues.id,
"attributes": {
"unicorn-name" : unicorn.dataValues.unicornName,
"unicorn-level" : unicorn.dataValues.unicornLevel,
"experience" : unicorn.dataValues.experience,
"hatches-at" : unicorn.dataValues.hatchesAt,
"is-hatched" : unicorn.dataValues.isHatched,
"raceEndsAt" : unicorn.dataValues.raceEndsAt,
"isRacing" : unicorn.dataValues.isRacing
},
"relationships": {
"staticrace": {
"data": {"type": "staticrace", "id" : unicorn.dataValues.staticRaceId}
},
"user":{
"data": {"type": "user", "id" : unicorn.dataValues.userId}
}
}
}
}
res.status(200).json(jsonObject);
In ember, you can call this by chaining model functions. For example when this unicorn goes to race in controllers\unicornracer.js:
raceUnicorn() {
if (this.get('unicornId') === '') {return false}
else {
return this.store.findRecord('unicorn', this.get('unicornId', { backgroundReload: false})).then(unicorn => {
return this.store.findRecord('staticrace', this.get('raceId')).then(staticrace => {
if (unicorn.getProperties('unicornLevel').unicornLevel >= staticrace.getProperties('raceMinimumLevel').raceMinimumLevel) {
unicorn.set('isRacing', true);
unicorn.set('staticrace', staticrace);
unicorn.set('raceEndsAt', Math.floor(Date.now()/1000) + staticrace.get('duration'))
this.set('unicornId', '');
return unicorn.save();
}
else {return false;}
});
});
}
}
The above code sends a PATCH to the api server route unicorns/:id
Final note about GET,POST,DELETE,PATCH:
GET assumes you are getting ALL of the information associated with a model (the example above shows a GET response). This is associated with model.findRecord (GET/:id)(expects one record), model.findAll(GET/)(expects an array of records), model.query(GET/?query=&string=)(expects an array of records), model.queryRecord(GET/?query=&string=)(expects one record)
POST assumes you at least return at least what you POST to the api server from ember , but can also return additional information you created on the apiServer side such as createdAt dates. If the data returned is different from what you used to create the model, it'll update the created model with the returned information. This is associated with model.createRecord(POST/)(expects one record).
DELETE assumes you return the type, and the id of the deleted object, not data or relationships. This is associated with model.deleteRecord(DELETE/:id)(expects one record).
PATCH assumes you return at least what information was changed. If you only change one field, for instance in my unicorn model, the unicornName, it would only PATCH the following:
{
data: {
"type":"unicorn",
"id": req.params.id,
"attributes": {
"unicorn-name" : "This is a new name!"
}
}
}
So it only expects a returned response of at least that, but like POST, you can return other changed items!
I hope this answers your questions about the JSON API adapter. Most of this information was originally gleamed by reading over the specification at http://jsonapi.org/format/ and the ember implementation documentation at https://emberjs.com/api/data/classes/DS.JSONAPIAdapter.html
I have an entity with a sequence attribute, which is an integer from 1-N for N members of the list. They are polyline points.
I want to be able to insert into the list at a given sequence point, and increment all the items at that point or beyond in the sequence to make room for the new item, and likewise if I delete then decrement everything above so we still have nice sequence ordering with no missing numbers.
There is a REST interface in this of course, but I dont want to hack about with that, I just want sequelize to magically manage this sequence number.
I am assuming I need to get hold of some "before insert" and "after delete" hooks in sequelize and issue some SQL to make this happen. Is that assumption correct or is there some cooler way of doing it.
I havent tested this, but this appears to be the solution, which is barely worth comment.
I know the modelName, and name==the attribute name,
options.hooks={
beforeInsert: function(record, options) {
return self.models[modelName].incrementAfter(name,record[name]);
},
afterDelete: function(record, options) {
return self.models[modelName].decrementAfter(name,record[name]);
}
}
and then added to my extended model prototype I have
incrementAfter:function(field,position){
return this.sequelize.query("UPDATE "+this.tableName+" SET "+field+" = "+field+"+1 WHERE "+field +" >= "+position);
},
decrementAfter:function(field,position){
return this.sequelize.query("UPDATE "+this.tableName+" SET "+field+" = "+field+"-1 WHERE "+field +" >= "+position);
},
Testing is simple when you have methods that you can call 100 times and they yield the same results. But how do you test something like an Api, where you have something like this:
int CreateUser(username,password); //returns the id of the user, -1 if error
int SubmitOrder(username,password,productName,quantity);//returns the id of the order -1 if error
int CancelOrder(username,password,orderId); //returns -1 if error
How would you test that this Api works? How do you create test data? I can not write unit tests fot it, I can not use the same test data, since I can not create a user two times(UserName is unique). When I submit an order I always get different orderIds as responses.
You need to find some way to "reset" system to well-known initial state, i.e. state with no users nor orders.
Also you need to find some way to observe state in the system. This way could be actually destructive, i.e. it could modify or even damage state of the system, but though. In your case, method CreateUser could be used as such observer to check whether user already exists, because it is known to return -1 in such situation.
Here is how one of your test cases could look like:
reset (); // Each test case should start with reset
assertNotEquals (-1, CreateUser ("foo", "bar")); // This should work fine
assertEquals (-1, CreateUser ("foo", "zoo")); // Make sure user "foo" does exist
assertNotEquals (-1, SubmitOrder ("foo", "bar", "apple", 1)); // Make sure user can pass authentication
assertEquals (-1, SubmitOrder ("foo", "zoo", "apple", 1)); // Make sure password is actually checked
The above test case checks that CreateUser actually creates user with given name and passwords, and does not allow creating two users with the same name.
Here is another test case:
reset ();
CreateUser ("foo", "bar");
orderID = SubmitOrder ("foo", "bar", "apple", 1); // Submit order
assertNotEquals (-1, CancelOrder (orderID)); // Make sure order was really created
assertEquals (-1, CancelOrder (orderID)); // Make sure order was cancelled
And so on. Of cause it would be better to find more straightforward ways to observe system state, e.g. by querying database directly.
I assume you are talking about some OOP language. I think you can solve your problem by Unit Testing and Dependency Injection.
Core concept:
first you do test of your DataBase class
when testing API you inject a FakeDataBase class into it (that shares same Interface)
So in testing environment API writes to some other fake database or simply prints queries to a file and you just check if content of this file is what you expected.
Great video:
http://www.youtube.com/watch?feature=player_embedded&v=wEhu57pih5w#!
http://en.wikipedia.org/wiki/Dependency_injection
http://en.wikipedia.org/wiki/Unit_testing
The following scenario is, I would say quite common and although I know one way of resolving it but it lack elegance.
The example I'm giving is based upon https://github.com/sharparchitecture/Sharp-Architecture-Cookbook.
The application I'm coding is an ASP.NET MVC application and has to support multiple users working on the same object.
The following scenario is an edge case but nevertheless a valid one.
Say you have two users working on the same object and whether the dB row can be updated depends upon the value of a particular field. To make it more concrete, let's say you have a Product and to keep things simple, this Product has "Name" and "QuantityInStock" fields.
Say that initially, there are 10 items of the Product and User1 and User2 want to buy this product. When both users are presented the initial form they are told that there are 10 of these items in stock. Now User1 buys all 10 items while User2 goes to have a coffee. So User1's transaction goes through no problem.
Then User2 comes back after his coffee in the belief that there are still 10 items in stock. So he tries to buy 1 but he must be prevented from doing so since there are no items in stock.
So this problem can be solved by using ASP.NET DataAnnotations validation and this will catch the majority of cases. However, in our edge case, say that User1 and User2 perform the same operation but within a fraction of a second such that when User2 submits the form, it passes the ASP.NET Validation but by the time it gets to the persistence layer, the QuantityInStock is 0.
The solution to this is to perform the validation at the latest moment as possible i.e. just before calling the Update method.
Now for some code.
public ProductModel CreateOrUpdate(ProductModel productModel)
{
var currentProductModel = Get(productModel.Id);
var currentQuantityInStock = currentProductModel.QuantityInStock;
if(currentProductModel.QuantityInStock !=0 && productModel.QuantityInStock >= currentQuantityInStock )
{
currentProductModel.QuantityInStock= productModel.QuantityInStock;
currentProductModel.Name = productModel.Name;
this.productModelRepository.SaveOrUpdate( currentProductModel );
return productModel;
}
else
{
//Raise an exception
}
}
Now, the fact that I'm calling:
var currentProductModel = Get(productModel.Id);
means that if I were to just do this:
this.productModelRepository.SaveOrUpdate( productModel );
would cause an exception:
a different object with the same identifier value was already associated with the session: 1
Hence, I have to copy all of the values from productModel to currentProductModel. It's fine when using something like Automapper but still kind of feels wrong to me in the sense that I feel I should just be able to save productModel as is without having to transfer the data from one object to another.
Moreover, having to do the same validation twice, once using DataAnnotation and another time just before updating violates the DRY principle.
The point is that I feel like I'm missing a trick but don't quite know where to start and what to investigate.
This to me is a simple problem but coming up with a nice elegant solution is something else. So the question is how have you dealt with this simple case in the past? Am I overthinking this?
have you tried optimistic Locking with Version?
// Fluent mapping
public EntitiyMap()
{
OptimisticLock.All(); // all properties musn't be changed in db when saving
// or
OptimisticLock.Dirty(); // only dirty properties musn't be changed in db when saving
}
//
public ProductModel CreateOrUpdate(ProductModel productModel)
{
try
{
// productModel is already validated and updated
this.productModelRepository.SaveOrUpdate( productModel );
return productModel;
}
catch (StaleObjectException)
{
// somebody changed the object in database after we have read it
// Raise an exception or whatever
}
}
Update: i handled such things in another way
public void BuySomething(ProductModel productModel, int amount)
{
int tries = 5;
bool success = false;
while(!success && tries > 0)
{
if (productModel.QuantityInStock <= amount)
{
//Raise an exception
}
productModel.QuantityInStock - amount;
try
{
this.productModelRepository.SaveOrUpdate( productModel );
}
catch (StaleObjectException)
{
// somebody changed the object in database after we have read it
this.productModelRepository.Refresh(productModel);
tries--;
}
}
if (tries <= 0)
{
// Raise an exception or whatever
}
}
zero extra roundtrips if nobody changed it in between, and guaranteed serialisation of the transactions
I've got an Account model object and a UNIQUE constraint on the account's Name. In Domain Driven Design, using nHibernate, how should I check for the name's unicity before inserting or updating an entity?
I don't want to rely on a nHibernate exception to catch the error. I'd like to return a prettier error message to my user than the obscure could not execute batch command.[SQL: SQL not available]
In the question Where should I put a unique check in DDD?, someone suggested using a Specification like so.
Account accountA = _accountRepository.Get(123);
Account accountB = _accountRepository.Get(456);
accountA.Name = accountB.Name;
ISpecification<Account> spec = new Domain.Specifications.UniqueNameSpecification(_accountRepository);
if (spec.IsSatisfiedBy(accountObjA) == false) {
throw new Domain.UnicityException("A duplicate Account name was found");
}
with the Specification code as:
public bool IsSatisfiedBy(Account obj)
{
Account other = _accountRepository.GetAccountByName(obj.Name);
return (other == null);
}
This works for inserts, but not when doing an update because. I tried changing the code to:
public bool IsSatisfiedBy(Account obj)
{
Account other = _accountRepository.GetAccountByName(obj.Name);
if (obj == null) { // nothing in DB
return true;
}
else { // must be the same object.
return other.Equals(obj);
}
}
The problem is that nHibernate will issue an update to the database when it executes GetAccountByName() to recover a possible duplicate...
return session.QueryOver<Account>().Where(x => x.Name == accntName).SingleOrDefault();
So, what should I do? Is the Specification not the right way to do it?
Thanks for your thoughts!
I'm not a fan of the specification pattern for data access, it always seems like jumping hoops to get anything done.
However, what you've suggested, which really just boils down to:
Check if it already exists.
Add if it doesn't; Show user-friendly message if it does.
... is pretty much the easiest way to get it done.
Relying on database exceptions is the other way of doing it, if your database and it's .NET client gracefully propagates the table & column(s) that were infringing the unique constraint. I believe most drivers don't do so (??), as they just throw a generic ConstraintException that says "Constraint XYZ was violated on table ABC". You can of course have a convention on your unique constraint naming to say something like UK_MyTable_MyColumn and do string magic to pull the table & column names out.
NHibernate has a ISQLExceptionConverter that you can plug into the Configuration object when you set NHibernate up. Inside this, you get exposed to the exception from the .NET data client. You can use that exception to extract the table & columns (using the constraint name perhaps?) and throw a new Exception with a user friendly message.
Using the database exception way is more performant and you can push a lot of the detecting-unique-constraint-violation code to the infrastructure layer, as opposed to handling each one case by case.
Another thing worth pointing out with the query-first-then-add method is that to be completely transaction safe, you need to escalate the transaction level to serializable (which gives the worst concurrency) to be totally bullet proof. Whether you need to be totally bullet proof or not, depends on your application needs.
You need to handle it with Session.FlushMode mode to set to FlushMode.Commit and use transaction to rollback if at all update fired.