Let's talk about it a little bit more. The assumption here was that the application on a regular basis uses an external data-source that is accessed via JNDI. In general it's a good practice to keep a data-source external to the application:
1. It's always possible to change the data-source without touching the application - let's say a bug was found in a data-source you are using. Or it should be configured differently. If a data-source embedded into an application and such a change is required, you will probably need to release patch. If the datasource is external, it would be enough just to change/reconfigure it.
2. In some deployments several applications can use the same datasource. Consider a Tomcat running with several wars: quite a common case, right? If a datasoure is embedded, each war has its own data-source. Usually this would be a waste of resources and duplication of a configuration.
3. And finally it would be possible to change a data-source for unit tests, which is exactly our use case.
For unit tests it's really convenient to use in-memory database. There are few databases implemented in java that provides this capability. My favorite are H2 and HSQL. In this example I have used HSQL, so here comes the jetty-ds-test.xml:
This is configuration of HSQL in memory. Notice sql.syntax_ora=true, which makes HSQL to use Oracle syntax. This is useful if you are using Oracle in production, but you want to use HSQL for unit testing or development.
So now you have at the beginning of a unit-test you have a Jetty server running with your application connected to in-memory HSQL database via JNDI. But something is still missing. This something is a database schema: to remind you, we have just started a new database in memory and it's empty. You probably already have a script that generates schema, tables, indexes and may be some data. Now you need to run it.
Actually there are several options how do it. One of the easiest is to use Springs's SimpleJdbcTestUtils. But first we'll need to add a dependency on spring-test in our pom.xml:
And here comes the code that runs the sql script:
In this snippet I load the sqlScriptFileName from the classpath. Usually it's convenient to place the script in src/test/resources, but if you don't like it, you can always load it from a different place by using other Resource implementations (e.g. URLResource is quite convenient).
As I have already said in this snippet I used Spring. If you are familiar with Spring, it is probably natural to you. If you don't - don't be afraid. Only the unit tests become dependent on Spring, but the actual application did not.
And now you are ready to start the testing.
Recommended Reading1. Next Generation Java Testing: TestNG and Advanced Concepts
2. Apache Maven 3 Cookbook
3. Spring Recipes: A Problem-Solution Approach