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Currently I am doing TDD on a reusable Django app. One test should make sure that my view only returns articles that have a publish-date that is in the past. I am quite new to testing in Django. So far I have learned how to use .json files as fixtures for my test classes.
However for this test I do not want to insert publish dates that are 1000 years in the future. After all another species might discover our ancient internet, check out my source and wonder why my test fails :) What other approaches are there to solve this problem? Static .json files seem to be a bit hard to maintain as well as the application grows... mocking the datetime.datetime.now() method in my tests feels tedious as well.
There must be an easy way to produce the .json fixture on the fly before the test runs and always have 2 days from now as the publish-date for some of my entries...
You could try subclassing the datetime functions (see "Using Mock objects in Django for testing the current date").
Mocking datetime was my first thought as well but as LaundroMat pointet out in his blog post himself, this is rather hacky and bad.
I came up with another solution:
I just gave up on .json fixtures. I don't even know why Django encourages to use them. They look ugly and they are impossible to maintain.
Instead I added a module test_data.py to my fixtures folder. That module imports my models and defines some nice methods that create test-data for me. In my tests.py I dropped the fixtures = ['some_json_file'] line and added a setUp() method instead. This method executes my 'dynamic fixtures' from my test_data.py module.
This is so simple and obvious that I wonder if there is anything wrong with this approach. If no one comments on this solution, I will mark is as accepted in a couple of weeks or so...
You can try using django dynamic fixture, it will fill date/time properties automatically for you.
Creating test data
Indeed it is far more flexible to create your test data with Python.
There are several packages that support such things, for instance
model-backery
django-dynamic-fixture
These two use fairly different approaches. Have a look and pick the one you like more.
You can also write data generation functions from scratch. If you partition your logic carefully, this is not overly cumbersome.
Handling time
For tests involving time, the right approach is indeed mocking -- but don't do it yourself, use a nice library. See for instance
freezegun
There is even a pytest plugin for it.
This question is more or less programming language agnostic. However as I'm mostly into Java these days that's where I'll draw my examples from. I'm also thinking about the OOP case, so if you want to test a method you need an instance of that methods class.
A core rule for unit tests is that they should be autonomous, and that can be achieved by isolating a class from its dependencies. There are several ways to do it and it depends on if you inject your dependencies using IoC (in the Java world we have Spring, EJB3 and other frameworks/platforms which provide injection capabilities) and/or if you mock objects (for Java you have JMock and EasyMock) to separate a class being tested from its dependencies.
If we need to test groups of methods in different classes* and see that they are well integration, we write integration tests. And here is my question!
At least in web applications, state is often persisted to a database. We could use the same tools as for unit tests to achieve independence from the database. But in my humble opinion I think that there are cases when not using a database for integration tests is mocking too much (but feel free to disagree; not using a database at all, ever, is also a valid answer as it makes the question irrelevant).
When you use a database for integration tests, how do you fill that database with data? I can see two approaches:
Store the database contents for the integration test and load it before starting the test. If it's stored as an SQL dump, a database file, XML or something else would be interesting to know.
Create the necessary database structures by API calls. These calls are probably split up into several methods in your test code and each of these methods may fail. It could be seen as your integration test having dependencies on other tests.
How are you making certain that database data needed for tests is there when you need it? And why did you choose the method you choose?
Please provide an answer with a motivation, as it's in the motivation the interesting part lies. Remember that just saying "It's best practice!" isn't a real motivation, it's just re-iterating something you've read or heard from someone. For that case please explain why it's best practice.
*I'm including one method calling other methods in (the same or other) instances of the same class in my definition of unit test, even though it might technically not be correct. Feel free to correct me, but let's keep it as a side issue.
I prefer creating the test data using API calls.
In the beginning of the test, you create an empty database (in-memory or the same that is used in production), run the install script to initialize it, and then create whatever test data used by the database. Creation of the test data may be organized for example with the Object Mother pattern, so that the same data can be reused in many tests, possibly with minor variations.
You want to have the database in a known state before every test, in order to have reproducable tests without side effects. So when a test ends, you should drop the test database or roll back the transaction, so that the next test could recreate the test data always the same way, regardless of whether the previous tests passed or failed.
The reason why I would avoid importing database dumps (or similar), is that it will couple the test data with the database schema. When the database schema changes, you would also need to change or recreate the test data, which may require manual work.
If the test data is specified in code, you will have the power of your IDE's refactoring tools at your hand. When you make a change which affects the database schema, it will probably also affect the API calls, so you will anyways need to refactor the code using the API. With nearly the same effort you can also refactor the creation of the test data - especially if the refactoring can be automated (renames, introducing parameters etc.). But if the tests rely on a database dump, you would need to manually refactor the database dump in addition to refactoring the code which uses the API.
Another thing related to integration testing the database, is testing that upgrading from a previous database schema works right. For that you might want to read the book Refactoring Databases: Evolutionary Database Design or this article: http://martinfowler.com/articles/evodb.html
In integration tests, you need to test with real database, as you have to verify that your application can actually talk to the database. Isolating the database as dependency means that you are postponing the real test of whether your database was deployed properly, your schema is as expected and your app is configured with the right connection string. You don't want to find any problems with these when you deploy to production.
You also want to test with both precreated data sets and empty data set. You need to test both path where your app starts with an empty database with only your default initial data and starts creating and populating the data and also with a well-defined data sets that target specific conditions you want to test, like stress, performance and so on.
Also, make sur that you have the database in a well-known state before each state. You don't want to have dependencies between your integration tests.
Why are these two approaches defined as being exclusively?
I can't see any viable argument for
not using pre-existing data sets, especially particular data that has
caused problems in the past.
I can't
see any viable argument for not
programmatically extending that data with
all the possible conditions that
you can imagine causing problems and even a
bit of random data for integration
testing.
In modern agile approaches, Unit tests are where it really matters that the same tests are run each time. This is because unit tests are aimed not at finding bugs but at preserving the functionality of the app as it is developed, allowing the developer to refactor as needed.
Integration tests, on the other hand, are designed to find the bugs you did not expect. Running with some different data each time can even be good, in my opinion. You just have to make sure your test preserves the failing data if you get a failure. Remember, in formal integration testing, the application itself will be frozen except for bug fixes so your tests can be change to test for the maximum possible number and kinds of bugs. In integration, you can and should throw the kitchen sink at the app.
As others have noted, of course, all this naturally depends on the kind of application that you are developing and the kind of organization you are in, etc.
It sounds like your question is actually two questions. Should you exclude the database from your testing? When you do a database, then how should you generate the data in the database?
When possible I prefer to use an actual database. Frequently the queries (written in SQL, HQL, etc.) in CRUD classes can return surprising results when confronted with an actual database. It's better to flush these issues out early on. Often developers will write very thin unit tests for CRUD; testing only the most benign cases. Using an actual database for your testing can test all kinds corner cases you may not have even been aware of.
That being said there can be other issues. After each test you want to return your database to a known state. It my current job we nuke the database by executing all the DROP statements and then completely recreating all the tables from scratch. This is extremely slow on Oracle, but can be very fast if you use an in memory database like HSQLDB. When we need to flush out Oracle specific issues we just change the database URL and driver properties and then run against Oracle. If you don't have this kind of database portability then Oracle also has some kind of database snapshot feature which can be used specifically for this purpose; rolling back the entire database to some previous state. I'm sure what other databases have.
Depending on what kind of data will be in your database the API or the load approach may work better or worse. When you have highly structured data with many relations, APIs will make your life easier my making the relations between your data explicit. It will be harder for you to make a mistake when creating your test data set. As mentioned by other posters refactoring tools can take care of some of the changes to structure of your data automatically. Often I find it useful to think of API generated test data as composing a scenario; when a user/system has done steps X, Y Z and then tests will go from there. These states can be achieved because you can write a program that calls the same API your user would use.
Loading data becomes much more important when you need large volumes of data, you have few relations between within your data or there is consistency in the data that can not be expressed using APIs or standard relational mechanisms. At one job that at worked at my team was writing the reporting application for a large network packet inspection system. The volume of data was quite large for the time. In order to trigger a useful subset of test cases we really needed test data generated by the sniffers. This way correlations between the information about one protocol would correlate with information about another protocol. It was difficult to capture this in the API.
Most databases have tools to import and export delimited text files of tables. But often you only want subsets of them; making using data dumps more complicated. At my current job we need to take some dumps of actual data which gets generated by Matlab programs and stored in the database. We have tool which can dump a subset of the database data and then compare it with the "ground truth" for testing. It seems our extraction tools are being constantly modified.
I've used DBUnit to take snapshots of records in a database and store them in XML format. Then my unit tests (we called them integration tests when they required a database), can wipe and restore from the XML file at the start of each test.
I'm undecided whether this is worth the effort. One problem is dependencies on other tables. We left static reference tables alone, and built some tools to detect and extract all child tables along with the requested records. I read someone's recommendation to disable all foreign keys in your integration test database. That would make it way easier to prepare the data, but you're no longer checking for any referential integrity problems in your tests.
Another problem is database schema changes. We wrote some tools that would add default values for columns that had been added since the snapshots were taken.
Obviously these tests were way slower than pure unit tests.
When you're trying to test some legacy code where it's very difficult to write unit tests for individual classes, this approach may be worth the effort.
I do both, depending on what I need to test:
I import static test data from SQL scripts or DB dumps. This data is used in object load (deserialization or object mapping) and in SQL query tests (when I want to know whether the code will return the correct result).
Plus, I usually have some backbone data (config, value to name lookup tables, etc). These are also loaded in this step. Note that this loading is a single test (along with creating the DB from scratch).
When I have code which modifies the DB (object -> DB), I usually run it against a living DB (in memory or a test instance somewhere). This is to ensure that the code works; not to create any large amount of rows. After the test, I rollback the transaction (following the rule that tests must not modify the global state).
Of course, there are exceptions to the rule:
I also create large amount of rows in performance tests.
Sometimes, I have to commit the result of a unit test (otherwise, the test would grow too big).
I generally use SQL scripts to fill the data in the scenario you discuss.
It's straight-forward and very easily repeatable.
This will probably not answer all your questions, if any, but I made the decision in one project to do unit testing against the DB. I felt in my case that the DB structure needed testing too, i.e. did my DB design deliver what is needed for the application. Later in the project when I feel the DB structure is stable, I will probably move away from this.
To generate data I decided to create an external application that filled the DB with "random" data, I created a person-name and company-name generators etc.
The reason for doing this in an external program was:
1. I could rerun the tests on by test modified data, i.e. making sure my tests were able to run several times and the data modification made by the tests were valid modifications.
2. I could if needed, clean the DB and get a fresh start.
I agree that there are points of failure in this approach, but in my case since e.g. person generation was part of the business logic generating data for tests was actually testing that part too.
Our team confront the same question recently.
Before, we were using specflow to do integration testing. With specflow, QA can write each test case inside which populating necessary test data to DB.
Now, QA want to use postman to test API, how can they populate the data? One solution is creating Apis for populating them. Another is sync historical data from Prod to test env.
Will update my answer once we try different solutions and decide which one to go.
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.
I'm setting up some Selenium tests for an internal web app and looking for advice on a testing 'best practice'. One of the tests is going to add some data via the UI that cannot be removed via the UI (e.g., you can add a record via the web app, but removing requires contacting someone internally to remove it at the database level). How do you typically account for cleaning up data after the Selenium test is run?
The app in question is written in PHP and I'm using PHP for testing (with Selenium RC and SimpleTest), but I'm open to other tools, etc. as this is just a broad best practice question. The app being tested is in our development environment, so I'm not particularly worried about data carrying over from tests.
Some ideas:
Manually connect to the database in the Selenium test to clean up the data
Use something like DBUnit to manage this?
Just add data and don't worry about cleaning it up (aka, the lazy approach)
Thanks!
Edit: Seems most of the ideas centered around the same conclusion: work off a known set of data and restore when the tests are finished. The mechanism for this probably will vary depending on language, an amount of data, etc. but this looks like it should work for my needs.
I use Selenium with a Rails application, and I use the fixture mechanism to load and unload data from the test database. It's similar to the DbUnit approach, though I don't unload and reload between tests due to the volume of data. (This is something I'm working on, though.)
We have a web front end to a database restore routine. First thing our tests do is restore a "well known" starting point.
Point the webapp to a different database instance that you can wipe when you are done with the tests. Then you will have the database to inspect after the tests have run if you need to debug, and you can just blow away all the tables when you are done. You could get an export of the current database and restore it into your fresh instance before the tests if you need seed data.
Avoid the lazy approach. It's no good and will ultimately fail you. See my previous response on this topic in this separate StackOverflow question.
Agree with the other answers here. I've wired in Selenium and DBUnit tests to the past 3 projects I've worked on. On the first project we tried the lazy approach, but predictably it fell in a heap, so we used DBUnit and I've not looked back.
I realize you are using PHP, so please translate DBUnit/JUnit to your PHP equivalents.
A couple of points:
Use as little data as possible. With
many selenium tests running, you want
the DBUnit load to be as quick as
possible. So try to minimize the
amount of data you are loading.
Only load the data that changes. Often
you can skip tables which are never
changed by the web app. Ref data
tables and so on. However you might
want to create a seperate DBUnit xml
file/db backup to load this data in
case you accidentally lose it.
Let the JUnit selenium tests choose
whether they need a reload. Some Selenium tests will not change any
data, so there is no point reloading
the database after they run. In each of my selenium tests I
override/implement a method to return the desired DBUnit behavior.
#Override
protected DBUnitRunConfig getDBUnitRunConfig() {
return DBUnitRunConfig.RUN_ONCE_FOR_THIS_TEST_CASE;
}
(Couldn't get that snippet to format correctly.) Where DBUnitRunConfig is:
public enum DBUnitRunConfig {
NONE,
RUN_IF_NOT_YET_RUN_IN_ANY_TEST_CASE,
RUN_ONCE_FOR_THIS_TEST_CASE,
RUN_FOR_EACH_TEST_IN_TEST_CASE
};
This cuts down the time required to get through the tests. The Selenium enabled super class (or helper class) can then run, or not run, DBUnit for the given tests.
I am introducing automated integration testing to a mature application that until now has only been manually tested.
The app is Windows based and talks to a MySQL database.
What is the best way (including details of any tools recommended) to keep tests independent of each other in terms of the database transactions that will occur?
(Modifications to the app source for this particular purpose are not an option.)
How are you verifying the results?
If you need to query the DB (and it sounds like you probably do) for results then I agree with Kris K, except I would endeavor to rebuild the DB after every test case, not just every suite.
This helps avoid dangerous interacting tests
As for tools, I would recommend CppUnit. You aren't really doing unit tests, but it shouldn't matter as the xUnit framework should give you the set up and teardown framework you'll need to automatically set up your test fixture
Obviously this can result in slow-running tests, depending on your database size, population etc. You may be able to attach/detach databases rather than dropping/rebuilding.
If you're interested in further research, check out XUnit Test Patterns. It's a fine book and a good website for this kind of thing.
And thanks for automating :)
Nick
You can dump/restore the database for each test suite, etc. Since you are automating this, it may be something in the setup/teardown functionality.
I used to restore the database in the SetUp function of the database related unit test class. This way it was ensured that each test runs under the same conditions.
You may consider to prepare special database content for the tests, i.e. with less data than the current production version (to keep the restore times reasonable).
The best environment for such testing, I believe, is VMWare or an equivalent. Set up your database, transaction log and so on, then record the whole lot - database as well as configuration. Then to re-test, reload the image and database and kick off the tests. This still requires maintenance of the tests as the system changes, but at least the tests are repeatable, which is one of your greatest challenges in integration testing.
For test automation, many people use Perl, but we've found that Perl programs grow like Topsy and become convoluted. The use of Python as a scripting language (we run C++ tests) is worthwhile if you're trying to build a series of structured tests.
As #Kris K. says dumping and restoring the database between each test will probably be the way to go.
Since you are looking at doing testing external to the App I would look to build the testing framework in a language where you can take advantage of better testing tools.
If you built the testing framework in Java you could take advantage of JUnit and potentially even something like FitNesse.
Don't think that just because the application under test is C++ that means you are stuck using C++ for your automated testing.
Please try AnyDbTest, I think it is the very tool you are finding. (www.anydbtest.com).
Features:
1.Writing test case with Xml, not Java/C++/C#/VB code. Not need those expensive programming tools.
2.Supports all popular databases, such as Oracle/SQL Server/My SQL
3.So many kinds of assertion supported, such as StrictEqual, SetEqual, IsSupersetOf, Overlaps, and RecordCountEqual etc. Plus, most of assertions can prefix logic not operator.
4.Allows using an Excel spreadsheet/Xml as the source of the data for the tests. As you know, Excel spreadsheet is to easily create/edit and maintain the test data.
5.Supports sandbox test model, if one test will be done in sandbox, all database operations on each DB will be rolled back meaning any changes will be undone.
6.Allows performing data pump from one database/Excel into target database in testing initialization and finalization phase. This is easy way to prepare the test data for testing.
7.Unique cross-different-type-database testing, which means target and reference result set can come from two databases, even one is SQL Server, another is Oracle.
8.Set style comparison for recordset. AnyDbTest will tell you what is the intersection, or surplus or absence between the two record sets.
9.Sequential style comparison for recordset or scalar values. It means the two result set will be compared in their original sequence.
10.Allow to export result set of SQL statement into Xml/Excel file.