Getting started with Scala, Scalatest, and Maven

Question

I created a new scala project with the following:

mvn org.apache.maven.plugins:maven-archetype-plugin:2.2:generate 
    -DarchetypeGroupId=org.scala-tools.archetypes 
    -DarchetypeArtifactId=scala-archetype-simple 
    -DarchetypeVersion=1.3 
    -DgroupId=myGroup 
    -DartifactId=myProject
    -Dversion=0.1.0 
    -DinteractiveMode=false

Which gives me the following POM:

 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <groupId>myGroup</groupId>
   <artifactId>myProject</artifactId>
   <version>0.1.0</version>
   <name>${project.artifactId}</name>
   <description>My wonderfull scala app</description>
   <inceptionYear>2010</inceptionYear>
   <licenses>
     <license>
       <name>My License</name>
       <url>http://....</url>
       <distribution>repo</distribution>
     </license>
   </licenses>

   <properties>
     <maven.compiler.source>1.5</maven.compiler.source>
     <maven.compiler.target>1.5</maven.compiler.target>
     <encoding>UTF-8</encoding>
     <scala.version>2.8.0</scala.version>
   </properties>

 <!--
   <repositories>
     <repository>
       <id>scala-tools.org</id>
       <name>Scala-Tools Maven2 Repository</name>
       <url>http://scala-tools.org/repo-releases</url>
     </repository>
   </repositories>

   <pluginRepositories>
     <pluginRepository>
       <id>scala-tools.org</id>
       <name>Scala-Tools Maven2 Repository</name>
       <url>http://scala-tools.org/repo-releases</url>
     </pluginRepository>
   </pluginRepositories>
 -->
   <dependencies>
     <dependency>
       <groupId>org.scala-lang</groupId>
       <artifactId>scala-library</artifactId>
       <version>${scala.version}</version>
     </dependency>

     <!-- Test -->
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
       <version>4.8.1</version>
       <scope>test</scope>
     </dependency>
     <dependency>
       <groupId>org.scala-tools.testing</groupId>
       <artifactId>specs_${scala.version}</artifactId>
       <version>1.6.5</version>
       <scope>test</scope>
     </dependency>
     <dependency>
       <groupId>org.scalatest</groupId>
       <artifactId>scalatest</artifactId>
       <version>1.2</version>
       <scope>test</scope>
     </dependency>
   </dependencies>

   <build>
     <sourceDirectory>src/main/scala</sourceDirectory>
     <testSourceDirectory>src/test/scala</testSourceDirectory>
     <plugins>
       <plugin>
         <groupId>org.scala-tools</groupId>
         <artifactId>maven-scala-plugin</artifactId>
         <version>2.15.0</version>
         <executions>
           <execution>
             <goals>
               <goal>compile</goal>
               <goal>testCompile</goal>
             </goals>
             <configuration>
               <args>
                 <arg>-make:transitive</arg>
                 <arg>-dependencyfile</arg>
                 <arg>${project.build.directory}/.scala_dependencies</arg>
               </args>
             </configuration>
           </execution>
         </executions>
       </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-surefire-plugin</artifactId>
         <version>2.6</version>
         <configuration>
           <useFile>false</useFile>
           <disableXmlReport>true</disableXmlReport>
           <!-- If you have classpath issue like NoDefClassError,... -->
           <!-- useManifestOnlyJar>false</useManifestOnlyJar -->
           <includes>
             <include>**/*Test.*</include>
             <include>**/*Suite.*</include>
           </includes>
         </configuration>
       </plugin>
     </plugins>
   </build>
 </project>

I can run mvn test and the sample tests run successfully. I'd like to use the most recent version of scala (I downloaded / installed 2.9.2...), but the most recent version of the org.scala-tools.testing scala_VERSION dependency seems to be 2.9.1. I made the following changes in my POM:

    <scala.version>2.9.1</scala.version>

and

    <dependency>
       <groupId>org.scala-tools.testing</groupId>
       <artifactId>specs_${scala.version}</artifactId>
       <version>1.6.5</version>
       <scope>test</scope>
    </dependency>

Now, running mvn test gives

 -------------------------------------------------------
  T E S T S
 -------------------------------------------------------
 Running samples.ListSuite
 Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.674 sec <<< FAILURE!
 initializationError(samples.ListSuite)  Time elapsed: 0.003 sec  <<< ERROR!
 java.lang.ClassCastException: scala.collection.immutable.Set$EmptySet$ cannot be
  cast to scala.collection.generic.Addable
         at org.scalatest.FunSuite$class.test(FunSuite.scala:1039)
         at samples.ListSuite.test(scalatest.scala:59)
         at samples.ListSuite.<init>(scalatest.scala:61)
         at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

         at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
         at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
         at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
         at java.lang.Class.newInstance0(Class.java:372)
         at java.lang.Class.newInstance(Class.java:325)
         at org.scalatest.junit.JUnitRunner.<init>(JUnitRunner.scala:62)
         at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

         at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
         at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
         at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
         at org.junit.internal.builders.AnnotatedBuilder.buildRunner(AnnotatedBuilder.java:31)
         at org.junit.internal.builders.AnnotatedBuilder.runnerForClass(AnnotatedBuilder.java:24)
         at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:57)
         at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:29)
         at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:57)
         at org.junit.internal.requests.ClassRequest.getRunner(ClassRequest.java:24)
         at org.apache.maven.surefire.junit4.JUnit4TestSet.execute(JUnit4TestSet.java:51)
         at org.apache.maven.surefire.suite.AbstractDirectoryTestSuite.executeTestSet(AbstractDirectoryTestSuite.java:120)
         at org.apache.maven.surefire.suite.AbstractDirectoryTestSuite.execute(AbstractDirectoryTestSuite.java:103)
         at org.apache.maven.surefire.Surefire.run(Surefire.java:169)
         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
         at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
         at java.lang.reflect.Method.invoke(Method.java:601)
         at org.apache.maven.surefire.booter.SurefireBooter.runSuitesInProcess(SurefireBooter.java:350)
         at org.apache.maven.surefire.booter.SurefireBooter.main(SurefireBooter.java:1021)

 Running samples.StackSuite
 Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.12 sec
 Running samples.AppTest
 Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 sec

 Results :

 Tests in error:
   initializationError(samples.ListSuite)

 Tests run: 4, Failures: 0, Errors: 1, Skipped: 0

 [INFO] ------------------------------------------------------------------------
 [INFO] BUILD FAILURE
 [INFO] ------------------------------------------------------------------------
 [INFO] Total time: 6.880s
 [INFO] Finished at: Wed Oct 10 01:10:56 ADT 2012
 [INFO] Final Memory: 9M/112M
 [INFO] ------------------------------------------------------------------------
 [ERROR] Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.6:test (default-test) on project myProject: There are test failures.
 [ERROR]
 [ERROR] Please refer to C:\Dropbox\work\dev\scalasandbox\target\surefire-reports for the individual test results.
 [ERROR] -> [Help 1]
 [ERROR]
 [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
 [ERROR] Re-run Maven using the -X switch to enable full debug logging.
 [ERROR]
 [ERROR] For more information about the errors and possible solutions, please read the following articles:
 [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

I presumably have some of the most simple tests possible (samples created by the maven archetype plugin), and bumping scala by a single minor version is breaking them? Should I just stick with scala 2.8 until the maven tools catch up?

Answer 1

Your artifact is outdated.

The latest version of Scala is 2.10. Currently ScalaTest is being distributed under different groupid and it supports the latest version of Scala. Here's the dependecy:

<dependency>
  <groupId>org.scalatest</groupId>
  <artifactId>scalatest_2.10</artifactId>
  <version>2.0.M5b</version>
  <scope>test</scope>
</dependency>

You will also require a different plugin:

  <plugin>
    <groupId>net.alchim31.maven</groupId>
    <artifactId>scala-maven-plugin</artifactId>
    <version>3.1.0</version>
    <executions>
      <execution>
        <phase>compile</phase>
        <goals>
          <goal>compile</goal>
          <goal>testCompile</goal>
        </goals>
      </execution>
    </executions>
  </plugin>

You don't need to specify any repositories, since all those artifacts are being distributed with the central repo.

Here's an example of a complete pom of a project depending on the Scala 2.10.