I have a DAO service which retrieves and saves data to Hibernate.
Could anybody point me to testing Methodology using JUnit for such service.
What is the best practice? When should I have passed test failed test and should I test exception?
You should test every possible path in your DAO. You would definitely use an in-memory database for your tests, such as HSQLDB.
One strategy would be to give the database some initial data in your setUp() method and clean it up on tearDown(), so all tests have a consistent working environment.
With these setup you can basically do everything... For example, if you want to test a save() method in your DAO, just add the new element and make sure that your table now has one more element. Moreover, fetch that element and compare it to the one you've inserted, it should obviously be the same.
Remember that you should always test every possible path.
I would also look into using DBUnit to ensure that your database is consistent and test independent. They have articles on how to get started and a tutorial. There a quite a few articles on IBM's DeveloperWorks blog as well that you might want to read.
I think using an in-memory database is often a good idea - for unit test. But the ideal is to combine fast unit tests with such a database with integration tests hitting the real database. There are subtle differences between, e.g., Hypersonic SQL and most production servers.
Consider using mocks for testing your error handling (i.e. mock the Hibernate session object and make it throw exceptions for certain operations)
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thank you for reading my question.
I was just wondering about how shall i create unit tests for existing database layer. as of now my project has existing unit tests but no unit test is written for database layer or any function which inserts / updates / deletes data from database.
We are using Microsoft tests. One approach I think here is
1) We shall create database on the fly i.e. mdf file and we will keep our defaults values ready in it and in our setup method(Nunit) or initialize method(MS tests) we will mock the objects and dump the dummy data into tables.
Also we are not using any mocking framework. So i am all confuse.
i need to know how can we do this from the scratch. Also is there anything optional available for mocking framework.
Any pointers or samples would be highly appreciated.
Thank you again.
A C# unit test shall not touch the database, you should mock the database. It should be possible to execute many thousands of unit test on your local machine (without external (internet, databases, other application)) within seconds (and you want to run them when you build your code).
That leaves us kind of with your question unanswered: what should your database layer tests do? It depends on what kind of logic you have in that assembly! If you have "business or decision" logic should should test that, if you have mapping logic test that. If all your database layer does if using (whatever db framework) to put the load on you database then you might not have anything worth testing there.
If you want to test logic performed by your database (say SP's) you should do that in the database project, and most likely not using mstest.
Of course you can use mstest to setup and tear down database and perform test, but those test will not be unit tests.
I am just starting to get into unit testing and cant see an easy way to do a lot of test cases due to the interaction with a database.
Is there a standard method/process for unit testing where database access (read and write) is required in order to assert tests?
The best I can come up with so far is to have a config file used to bootstrap my app using a different db connection and then use the startup method to copy over the live db to a db used in isolation for tests?
Am I close? Or is there a better approach to this?
Your business logic shouldn't directly interact with the Database. Instead it should go through a data access layer that you can fake and mock in the context of unit testing. Look into mocking frameworks to do the mocking for you. Your tests should not depend on a database at all. Instead you should specify the data returned from your data access layer explicitly, and then ensure that your business logic behaves correctly with that information.
Testing that the program works with a DB attached is more of an integration test, and those have a lot of costs associated with them. They are slower (so it's harder to run them every time you compile), and more complicated (so they require more time and effort to maintain). If you can get simpler unit tests in place, I would recommend you do that first. Later you can add integration tests that might use the DB as well, but you'll get the most value from adding simpler unit tests first.
As far as unit-test go, I think whatever works for you in practice is the way to go. It's important that unit tests give you some value and improve the quality of your system and your ability to develop and maintain it.
I would suggest you probably don't want to be copying the live db over to your test db. There's probably no guarantees that your live database will contain suitable data that will cause your unit-tests to consistently run. The unit-tests should test that your code works, they shouldn't be testing that the live database happens to contain suitable data that causes them to pass, because as it's live, your users might change the content of it so that your tests fail.
You're unit test code itself should probably populate your test db with data required that simulates the scenarios you want to write unit tests for. I messed around with some ruby on rails code a few years ago; the test framework for that would have a test class which setup the db with some fake data, then multiple test methods from the class would be written to run against that data, and the tear-down method would wipe data from the database. So, different test-classes (or sometimes people call them fixtures) would run against a certain data setup, that meant you could run a number of tests against the same data setup instead of creating it for every test case you wanted to run. Setting up data for every test could end up causing your tests to run slowly, such that you get bored of waiting for them to run and stop bothering with them.
I've set up unit tests that test a fake repository and tests that make use of a fake repository.
But what about testing the real repository that hits the database ? If this is left to integration tests then it would be seem that it isn't tested directly and problems could be missed.
Am I missing something here?
Well, the integration tests would only test the literal persistence or retrieval of data to and from the layer of persistence. If your repository is doing any kind of logic concerning that data (validation, throwing exceptions if an object isn't found, etc.), that can be unit tested by faking what the persistence layer returns (whether it returns the queried object, a return code, or something else). Your integration test will assure you that the code can physically persist/retrieve data from persistence, and that's it. Any sort of logic to test ought to belong in a unit test.
Sometimes, however, logic could exist in the persistence layer itself (e.g. stored procedures). This could be for the sake of efficiency, or it could merely be legacy code. This is harder to properly unit test, as you can only access the logic by getting to the database. In this scenario, it'd probably be best to try and move the logic to your code base as much as possible, so that it can be tested more easily. There probably exist unit testing frameworks for scenarios such as these, but I'm not aware of them (merely out of inexperience).
Can you set up a real repository that tests against a fake database?
Regardless of what you do, this is integration testing, not unit testing.
I'd definitely suggest integration tests against the DAL, within reason.
We don't use the Repository pattern per se (to our chagrin), but our policy for similar classes (Searchers) is as follows:
If the method does a simple retrieve from the database using an O/RM call, don't test it.
If the method uses query-building features of the O/RM, test it.
If the method contains a string (such as a column name), test it.
If the method calls a stored procedure, test it.
If the method contains logic, test it. But try to avoid logic.
If the method bypasses the O/RM and uses raw SQL, test it. But really try to avoid this.
The gist is you should know your O/RM works (and hopefully has tests), so there's no reason to test basic CRUD behavior.
You'll definitely want a "test deck" - an in-memory database, a local file-backed database that can be checked into source control, or (if you have to) a shared database. Some testing frameworks offer rollback facilities to restore the database state; just be careful if you're hitting multiple databases in the same test or (in some cases) if you have embedded transactions.
EDIT: Note that these integration tests will still test your repository in "isolation" (save for the database). All your other unit tests will use a fake repository.
I recently covered a very similar question over here.
In summary: test your concrete Repository implementations if there's value in doing so. If you are doing something complex in your implementation, it is probably a good idea to test it. If you are using an ORM with no custom logic, there may not be much value in writing tests at that level.
When unit testing, is it a must to use a database when testing CRUD operations?
Can sql lite help with this? Do you have to cre-create the db somehow in memory?
I am using mbunit.
No. Integrating an actual DB would be integration testing. Not unit testing.
Yes you could use any in-memory DB like SQLite or MS SQL Compact for this if you can't abstract (mock) your DAL/DAO in any other way.
With this in mind I have to point out, that unit testing is possible all the way to DAL, but not DAL itself. DAL will have to be tested with some sort of an actual DB in integration testing.
As with all complicated question, the answer is: It depends :)
In general you should hide your data access layer behind an interface so that you can test the rest of the application without using a database, but what if you would like to test the data access implementation itself?
In some cases, some people consider this redundant since they mostly use declarative data access technologies such as ORMs.
In other cases, the data access component itself may contain some logic that you may want to test. That can be an entirely relevant thing to do, but you will need the database to do that.
Some people consider this to be Integration Tests instead of Unit Tests, but in my book, it doesn't matter too much what you call it - the most important thing is that you get value out of your fully automated tests, and you can definitely use a unit testing framework to drive those tests.
A while back I wrote about how to do this on SQL Server. The most important thing to keep in mind is to avoid the temptation to create a General Fixture with some 'representative data' and attempt to reuse this across all tests. Instead, you should fill in data as part of each test and clean it up after.
When unit testing, is it a must to use a database when testing CRUD operations?
Assuming for a moment that you have extracted interfaces round said CRUD operations and have tested everything that uses said interface via mocks or stubs. You are now left with a chunk of code that is a save method containing a bit of code to bind objects and some SQL.
If so then I would declare that a "Unit" and say you do need a database, and ideally one that is at least a good representation of your database, lest you be caught out with vender specific SQL.
I'd also make light use of mocks in order to force error conditions, but I would not test the save method itself with just mocks. So while technically this may be an integration test I'd still do it as part of my unit tests.
Edit: Missed 2/3s of your question. Sorry.
Can sql lite help with this?
I have in the past used in memory databases and have been bitten as either the database I used and the live system did something different or they took quite some time to start up. I would recommend that every developer have a developer local database anyway.
Do you have to cre-create the db somehow in memory?
In the database yes. I use DbUnit to splatter data and manually keep the schema up to date with SQL scripts but you could use just SQL scripts. Having a developer local database does add some additional maintenance as you have both the schema and the datasets to keep up to data but personally I find is worth while as you can be sure that database layer is working as expected.
As others already pointed out, what you are trying to achieve isn't unit testing but integration testing.
Having that said, and even if I prefer unit testing in isolation with mocks, there is nothing really wrong with integration testing. So if you think it makes sense in your context, just include integration testing in your testing strategy.
Now, regarding your question, I'd check out DbUnit.NET. I don't know the .NET version of this tool but I can tell you that the Java version is great for tests interacting with a database. In a few words, DbUnit allows you to put the database in a known state before a test is run and to perform assert on the content of tables. Really handy. BTW, I'd recommend reading the Best Practices page, even if you decide to not use this tool.
Really, if you are writing a test that connects to a database, you are doing integration testing, not unit testing.
For unit testing such operations, consider using some typed of mock-database object. For instance, if you have a class that encapsulates your database interaction, extract an interface from it and then create an inheriting class that uses simple in-memory objects instead of actually connecting to the database.
As mentioned above, the key here is to have your test database in a known state before the tests are run. In one real-world example, I have a couple of SQL scripts that are run prior to the tests that recreate a known set of test data. From this, I can test CRUD operations and verify that the new row(s) are inserted/updated/deleted.
I wrote a utility called DBSnapshot to help integration test sqlserver databases.
If your database schema is changing frequently it will be helpful to actually test your code against a real db instance. People use SqlLite for speedy tests (because the database runs in memory), but this isn't helpful when you want to verify that your code works against an actual build of your database.
When testing your database you want to follow a pattern similar to: backup the database, setup the database for a test, exercise the code, verify results, restore database to the starting state.
The above will ensure that you can run each test in isolation. My DBSnapshot utility will simplify your code if your writing it .net. I think its easier to use than DbUnit.NET.
What is the best practice for testing an API that depends on data from the database?
What are the issues I need to watch out for in a "Continuous Integration" environment that runs Unit Tests as part of the build process? I mean would you deploy your database as part of the build scripts (may be run your installer) or should I go for hardcoded data [use MSTest Data Driven Unit Tests with XML]?
I understand I can mock the data layer for Business Logic layer but what if I had issues in my SQL statements in DAL? I do need to hit the database, right?
Well... that's a torrent of questions :)... Thoughts?
As far as possible you should mock out code to avoid hitting the database altogether, but it seems to me you're right about the need to test your SQL somewhere along the line. If you do write tests that hit the database, one key tip for avoiding headaches is to make sure that your setup gets the data into a known state, rather than relying on there already being suitable data available.
And of course, never test against your live database! But that goes without saying :)
As mentioned, use mocking to simulate DB calls in unit tests unless you want to fiddle with your tests and data endlessly. Testing sql statements implies more of an integration test. Run that separate from unit tests, they are 2 different beasts.
It's a good idea to automatically wipe the test database and then populate it with test harness data that will be assumed to be there for all of the tests that need to connect to the database. The database needs to be reset before each test for proper isolation - a failing test that puts in bad data could cause false failures on tests that follow and it gets messy if you have to run tests in a certain order for consistent results.
You can clear and populate the database with tools (DBUnit, DBUnit.NET, others) or just make your own utility classes to do the same thing.
As you said, other layers should be sufficiently decoupled from classes that actually hit the database, so the need for any kind of database being involved in testing is limited to tests run a small subset of your codebase. Your database accessing components can be mocked/stubbed for everything that depends on them.
One thing I did was create static methods that returned test data of a known state. I would then use a "fake" DAL to return this data as if I was actually calling the database. As for testing the sql/stored procedure, I tested it using SQL Management Studio. YMMV!