How do you go about integration testing your database through your domain layer/model (repositories) that uses LINQ 2 SQL in the implementation and leave the DB as you found it? In other words, the ideal world of unit testing the DB, the integration test would leave the DB as it found it.
Are there tools out there that will handle this automagically? What are the best practices for performing integration tests on a DB through repositories?
The Spring Framework provides support for integration testing when using NUnit. The NUnit classes are located in the assembly Spring.Testing.NUnit.dll. In there are some classes that perform transaction management. These classes create and roll back a database transaction for each test. You simply write code that can assume the existence of a transaction.
Whether or not this will actually work with Linq to SQL is another matter. Spring says this works with ORMs. SQL Server 2008 allows you to nest transactions, so in theory you could start a transaction, perform your test through the Linq to SQL classes, and then
roll your transaction back. But I haven't
tried it.
Ryan Garaguay has an interesting article about this which uses TransactionScope and NUnit to roll back the database changes (although he is using SQLCommand and SQLConnection objects in his test code, rather than Linq)
Related
I'm integrating SQL database (PostgreSQL) into my first ever Java backend system.
My dilemma now is should the application create the database and the tables by itself, or should it just assume that the required database initialized with the tables will be available?
If the application should not manage the database by itself, then what's the best approach to reproducing the database on developers' machines (I want to be able to run integration tests with real database locally)?
I ended up using FlyWay as #Max suggested in his comment.
The setup was quite easy and intuitive. I used the default settings for time being.
Setup of integration testing on development machine was a breeze.
The only thing that I don't particularly like is that cleaning the database between tests using FlyWay is very slow because it doesn't just clean the tables, but erases the entire scheme.
This, however, is not a big issue for me right now (currently have ~100 tests), and, probably, will not be difficult to optimize in the future if needed.
The majority of my integration tests use spring's AbstractTransactionalSpringContextTests to do a rollback instead of commiting to the database. This works well normally but because foreign key constraints are not applied until the commit stage there's a hole in my testing strategy.
How can I improve my tests?
I want to avoid commiting if possible as this causes tests to take much longer to run (when there are many)
I understand you don't want to commit to the database e.g. flush the session, but performance might be acceptable when using an in-memory sqlite database for this purpose.
I've done unit tests using NHibernate (with Fluent NHibernate) and an in-memory sql-lite database (how to here); this works quite fast as long as you only create the relevant parts of your database instead of the complete schema.
You can easily extend the AbstractTransactionalSpringContextTests class to flush to the db, see the spring.net docs 22.2.10 or this thread on the spring.net forum, so you should be able to get this working quickly for your test suite.
The dev tools for SQL in Visual Studio are great.
Is it possible to develop an app for Microsoft SQL Server, and then deploy a MySQL-compatible database instead?
The dev tools for Microsoft SQL Server are really nice (i.e. LINQ support), but a MySQL-compatible column database has better performance for huge datasets.
You would need to use MySql .net connector
http://dev.mysql.com/doc/refman/5.1/en/connector-net.html
With this, you get some of the functionality that you have with SQL server (entity framework, designer, etc) there are still a bunch of things that are not supported, but it's a good start
It's possible, but a number of specifics might tend to prevent a full implementation on SQL Server, particularly with respect to stored procedures.
However, if the intent is to build a scaffolding on VisStudio and finish the development using the MySQL tools, it would work okay. You'll have to learn both SQLs quite thoroughly. The sooner you do that, the less grief there will be in the conversion.
One method for doing this would be to abstract away the database itself. That be done at least a couple of ways; the first way, you could use classes to build the SQL that your application requires, and then just use that; then all that has to happen is that it has to know how to generate the right SQL for the right server. One of the drawbacks of doing it that way, though, is that if you depend on functionality that exists on only one DBMS, you'll have to emulate it in that abstraction layer.
The other method that you could use is to create two versions of your classes that talk to the RDBMS, one for MySQL and one for Microsoft's SQL Server. Use an interface and derive from it in order to do the actual implementation. Of course, you'll want to make sure that the only responsibility of the class is to interact with the database, so if you're doing this for business layer objects, you'll be implementing those sorts of things with two classes: a low-level one for the database API, and a high-level one for actually providing the API that your application is going to consume.
Perhaps not a direct answer to your question, but the dblinq project may be of use to you.
It may be worth a look just to see the MySQL implementations within the project in order to determine what the real differences between SQL Server and MySQL are going to be and how they're going to affect you. The more you can abstract out those differences behind a dependency implementation, the easier it'll be to swap out one implementation for another.
You can write your code for SQL Server and then switch to Devart LinqConnect.
For example, you can create a LINQ to SQL model using Entity Developer (in VS integration mode or in standalone mode), then change the connection to the MySQL-specific one and run Update Database from Model wizard (don't forget to select the Regenerate Storage check box).
As a result, you will obtain a MySQL database, having structure identical to the SQL Server one.
I am not a Db guy. I am just curious if there is a possibility to write asserts in Sql so that you can write unit tests for your scripts, for your sprocs etc. and then even implement a Test Driven Development approach to your sessions?
thanks!
You can do that actually, not directly from SQL throught, but the language you do your application.
Of cause you SQL must be incapsulated in DAL (Data Access Layer) and all data got by Repositories (or other data access classes). You can do unit testing of those classes, that would be running SQL scripts at the end. So, basically you will test your SQL code.
It is simplier to me, than trying to write such tests in SQL. :)
Sometime ago I had thought on that:
http://www.beletsky.net/2010/11/testing-database-and-test-database.html
I am trying to start a new MVC project with tests and I thought the best way to go would have 2 databases. 1 for testing against and 1 for when I run the app and use it (also test really as it's not production yet).
For the test database I was thinking of putting create table scripts and fill data scripts within the test setup method and then deleting all this in the tear down method.
I am going to be using Linq to SQL though and I don't think that will allow me to do this?
Will I have to just go the ADO route if I want to do it this way? Or should I just use a mock object and store data as an array or something?.
Any tips on best practices?
How did Jeff go about doing this for StackOveflow?
What I do is define an interface for a DataContext wrapper and use an implementation of the wrapper for the DataContext. This allows me to use an alternate, fake DataContext implementation in my tests (or mock it, if easier). This abstracts the database out of my unit tests completely. I found some starter code at http://andrewtokeley.net/archive/2008/07/06/mocking-linq-to-sql-datacontext.aspx, although I've extended it so that it handles the validation implementations on my entity classes.
I should also mention that I have a separate staging server for QA, so there is live testing of the entire system. I just don't use an actual database in my unit testing.
I checked out the link from tvanfosson and RikMigrations and after playing about with them I prefer the mocking datacontext method best. I realised I don't need to create tables and drop them all the time.
After a little more research I found Stephen Walther's article http://stephenwalther.com/blog/archive/2008/08/17/asp-net-mvc-tip-33-unit-test-linq-to-sql.aspx which to me seems easier and more reliable.
So I am going with this implementation.
Thanks for the help.
You may want to find some other way around actually hitting the database for your unit tests because it takes a lot more time. That being said, have you considered using Migrations for creating / deleting your tables instead of using sql scripts? RikMigrations is what I have been using to create my database so I can easily revision all of my code in one place. Justin Etheredge has a great article on using RikMigrations.
Consider these methods on DataContext:
http://msdn.microsoft.com/en-us/library/system.data.linq.datacontext.createdatabase.aspx
http://msdn.microsoft.com/en-us/library/system.data.linq.datacontext.executecommand(v=VS.100).aspx
I agree with much of the above, relating to unit testing. However, I think it's important to raise the point that using Mock Repositories and unit tests doesn't give you the same level of tests as a DB Integration Test would.
For example, our databases often have cascading deletes built right in to the schema. In this case, deleting a primary entity in an aggregate will automatically delete all child entities. However, this would not automatically apply in a mocked repository that was not backed up by a physical database with these business rules (unless you built all of those rules in to the Mock). This is important because if somebody comes along and changes the design of my schema, I need it to break my tests so I can adjust the code/schema accordingly. I appreciate that this is Integration Testing and not Unit Testing but thought it was worth mentioning.
My preferred option is to create a Master Design Database that contains sample data (the same sort of data you would create in your Mocks). During the start of each test run, I have an automated script that creates a backup of the MasterDB and restores it to "TestDB" (which all my tests use). That way, I maintain a repository of clean test data in Master than recreates itself upon each test run. My tests can play around with the data and test out all the scenarios needed.
When I debug the application, I have another script that backs up and restores the Master DB to a DEV database. I can play around with data here too without worrying about losing my sample data. I don't typically run this particular script every session because of the delay waiting for the DB to be recreated. I may run it once a day and then play around/debug the app throughout the day. If for example, I delete all the records from a table as part of my debugging, I would run the script to recreate the DevDB when I'm done.
These steps sound like they would add a huge amount of time to the process, but actually - they don't. Our application currently has in the region of 3500 tests, with about 3000 of them accessing the DB at some point. The database backup and restore typically takes around 10-12 seconds at the start of each test run. And since the whole test suite is only executed upon TFS checkin, we don't mind if we have to wait a while longer anyway. On an average day, our entire test suite takes about 15-20 minutes to run.
I appreciate and accept that integration testing is much slower than unit testing (because of the inherent need to use a real DB) but it more closely represents the 'real world' app. For example, Mock Repositories don't return DB error codes, the don't time-out, they don't lock up, they don't run out of disk space, etc.
Unit tests are ok for simple calculations, basic business rules, etc. and certainly they are absolutely the best choice for most operations that don't involve DB (or other resource) access. But I don't think they are as valuable as integration tests - people talk a lot about unit tests, but little is said about integration tests.
I expect those passionate about unit tests will be sending flames my way for this. That's fine - I'm just trying to bring some balance and to remind people that projects that are full of passed unit tests can still fail badly the moment you implement them in the field.
This article gives example of mocking linq to sql with typemock.
http://blog.benhall.me.uk/2007/11/how-to-unit-test-linq-to-sql-and.html