(Stubbed Cassandra) is a new open source tool for testing applications that interact with Cassandra.
The first release is primarily aimed at Java developers. Subsequent releases will be aimed at people writing black
box acceptance tests.
It works by implementing the server side of the CQL binary protocol, meaning that Cassandra drivers, such as the
the Datastax Java Driver, believe it to be a real Cassandra.
The original motivation for developing Scassandra was to test edge case / failure scenarios. However it quickly
became apparently it is just as useful with regular happy path unit tests.
So how does it work?
When you start Scassandra it opens two ports:
- Binary port: this is the port you'll configure your application with rather than the binary or a real
- Admin port: this is for Scassandra's REST API that provides priming and retrieving a list of executed
By default, when your application connects to Scassandra and executes queries Scassandra will respond with a result
with zero rows.
Then via Scassandra Java Client, and later the REST API, you can prime Scassandra to return
rows (where you can specify the column types and values), read request time outs, write request time outs and
After you've run your tests you can verify the queries and prepared statements that
your application has executed. Including the consistency the queries have been executed with. So if you have
requirements to execute certain writes at a high consistency but other queries can be at a lower consistency this
can be tested via black box acceptance tests.
The benefits of Scassandra over testing against a real
- Test failures deterministically: where previously you would need to have a multi node cluster with the
ability to bring down nodes.
- Test the consistency of queries. This has come up at my workplace where a requirement was that for most
queries we can downgrade consistency when there are failures but for certain important writes they had to be
executed at QUORUM.
- Have fast running DAO tests that don't require mocking out driver classes or a real Cassandra running.
So how do I use Scassandra?
The first release of Scassandra is aimed at Java developers. Scassandra
comes in two parts:
- Scassandra server. This is a Scala application that has been put in Maven central with a pom that will bring
in its transitive dependencies.
- Scassandra Java client. A thin wrapper written in Java to make using Scassandra from Java tests easy. This
has methods to start/stop Scassandra and classes that prime / retrieve the list of executed queries.
For the first release it is expected that Scassandra will only be used via the Java client and no one will use
it as a standalone executeable or interact with the REST API directly.
To get started with the Scassandra
Java client then go here
. Or checkout the example project here
If you aren't
using Java or a language that can easily use the Java client then the next release will be for you where we'll build
a standalone executable and from that release on we'll make the REST API backward compatible as we'll expect people
to use it directly.
It is all open source on github and you can find Scasandra server here
The Java client is here
And all the details of the
REST API e.g how to prime are on the Scassandra sever website here