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Thanks for hanging in and reading all this way. We ve covered a lot of ground so far. We ve discussed the Scala language and developed a whole bunch of idioms for building applications using Scala. We ve explored how Scala can be used by different team members in different ways. We ve seen how Scala allows you to compose fine-grained pieces of code together into complex systems that work well together. But no technology is an island. No matter how good Scala is in the abstract, it s only valuable if it can help your organization produce better and more maintainable code, faster. The good news is that Scala compiles down to JVM bytecode and works great with existing Java libraries. If you re working at a Java shop, the cost of using Scala on some projects is minimal. You can test Scala with your existing Java test tools. You store compiled Scala code in JAR and WAR files, so it looks and feels to the rest of your organization like what they re used to, Java bytecode. The operational characteristic of Scala code on web servers is indistinguishable from the operational characteristics of Java code. In this chapter, we re going to explore the practicalities of integrating Scala into your project and perhaps your organization. We ll look at testing Scala code, potential changes to team structure, best practices to look for during code reviews, and selling Scala into your organization. Let s start by looking at testing and Scala.

So far, we ve talked a lot about the type of testing that Scala code does not need. You do not need to write tests that catch type errors or test that method names exist. You can use Option to avoid null pointer problems. You use Scala s type system and strong typing to ensure that your code is well formed and valid. That does not mean that your logic is correct; therefore you need to write tests to ensure that the logic of your program is correct. I find that Behavior-Driven Development (BDD) provides the best way to write tests because business people can read and understand BDD, and BDD tests tend to be higher-level and focus on the logic, not the mechanics, of code.

Scala can be tested using existing Java frameworks including JUnit. However, there are better ways to test Scala code, and these better ways play nicely with JUnit and other Java testing frameworks. That means you get a better way to write Scala tests, but they run the same old ways. It s the best of both worlds. In this section, I m going to give a brief overview of two Scala test frameworks: Specs and ScalaTest.

Specs1 is a Behavior-Driven Design framework.2 Tests are expressed in a domain-specific language that is very descriptive and readable. For example, here s a Specs definition for testing some of Lift s utility classes:

class BoxSpecTest extends Runner(BoxSpec) with JUnit with Console object BoxSpec extends Specification { "A Box" can { "be created from a Option. It is Empty if the option is None" in { Box(None) mustBe Empty } "be created from a Option. It is Full(x) if the option is Some(x)" in { Box(Some(1)) must_== Full(1) }

Specs provides a lot of different matchers that allow you to test Strings by testing them against a regular expression:

"'hello world' matches 'h.* w.*'" in { "hello world" must beMatching("h.* w.*") }

<a><b><c><d></d></c></b></a> must \\("c").\("d")

Specs integrates with JUnit so that you can use your existing testing infrastructure to run Specs tests. The line

is all that s required to integrate with JUnit. The BoxSpecsTest can be run with your JUnit runner of choice. Specs also integrates with jMock 2.

1. http://code.google.com/p/specs/ 2. http://behaviour-driven.org/