Comments on: Getting Into Scala

By: Symphonious » Using Scala in .NET

Symphonious » Using Scala in .NET — Mon, 19 Oct 2009 14:29:34 +0000

[...] « Getting Into Scala [...]

By: Adrian Sutton

Adrian Sutton — Mon, 19 Oct 2009 08:03:04 +0000

ScalaTest gives fine error messages, horrible stack traces. Specs does too if you limit yourself to a JUnit model of writing tests but then you don’t get the nice nested structure of Specs. The problem with ScalaTest is that it’s just too hard to get setup and working properly and I happen to like many of the features of Specs.

The problem with not being able to run all the tests is a lack of tooling thing, hence it’s Scala related. I can run all the tests in my project for Java, I can’t for Scala without resorting to running ant. NetBeans handles this the best because it just picks up on the Ant JUnit test but then it has no support for Specs style test names etc.

By: Andrew Herron

Andrew Herron — Mon, 19 Oct 2009 07:59:11 +0000

The video we watched in the office was demonstrating ScalaTest – and the JUnit runner gave acceptable error messages (from memory, this was a while ago). Might be worth trying it again :)

Also the only-run-one-package issue you had in IntelliJ is more of an IDE thing than a Scala thing. There is a way to run all tests in a project, I just haven’t found it yet…

By: Adrian Sutton

Adrian Sutton — Sat, 17 Oct 2009 10:19:59 +0000

Yeah I’ve seen sbt mentioned a few times but we have a lot of internal systems that are setup to work with ant already so changing build tools isn’t really something I want to take on.

By: andrew cooke

andrew cooke — Fri, 16 Oct 2009 20:48:14 +0000

Hi, Your experience tallies pretty much with my own, but I wanted to mention sbt (Simple Build Tool) which is the one Scala-related tool that I have been really happy with. It’s a bit like Maven, but much easier to use (and although the community is way smaller the support has been great). http://code.google.com/p/simple-build-tool/ Cheers, Andrew

By: Adrian Sutton

Adrian Sutton — Fri, 16 Oct 2009 16:53:48 +0000

I guess what I’m getting at is really – Java winds up using a lot of “bad” stubs. Scala avoids most of them but yes you do still wind up with “good” stubs. :)

By: Adrian Sutton

Adrian Sutton — Fri, 16 Oct 2009 16:49:33 +0000

To some extent it’s a stub yes, but it’s very much not like stubs in Java – the key difference being that it implements a well defined and *separate* interface, rather than just stubbing out a part of the class.

In other contexts yes, you may still wind up using stubs and mocks in a very similar to Java context, but Scala essentially makes it easier for them to be clearly separate concerns.

By: Stephan Schmidt

Stephan Schmidt — Fri, 16 Oct 2009 16:46:34 +0000

One additional remark: HardCodedString is in your case a stub. And Mocks help with different things than stubs, so you still need them.

By: Adrian Sutton

Adrian Sutton — Fri, 16 Oct 2009 08:14:21 +0000

Thanks Jorge,
That’s great to know. Eclipse was messing up all over the place with dual sources but it sounds like that’s just an Eclipse thing – I’ll have to try it again with IntelliJ.

Your scala-javautils library looks promising – I’ll certainly keep an eye on it as it matures. Thanks for pointing it out.

By: Jorge Ortiz

Jorge Ortiz — Fri, 16 Oct 2009 07:30:58 +0000

Hi Adrian,

You can have mixed Java/Scala projects with bidirectional dependencies, it just involves a little more complication in the build system. 1) Invoke scalac on both Java and Scala sources. Scalac can understand Java sources enough to know what their type signatures should be, and uses that to compile the Scala source as if the necessary Java classes were there. 2) Invoke javac on the Java sources, with the Scala classes in the classpath. This will compile your Java code. Sometimes another step is needed, 3) run scalac on your Scala sources, with the compiled Java classes in your classpath. This third step is sometimes, but not always necessary.

Also, to convert collections bidirectionally between Java and Scala, take a look at my open source project: http://github.com/jorgeortiz85/scala-javautils/tree/master

Cheers,

–j