issue - creating a directory with gradle not worki

I have the following build.gradle:

task wrapper(type: Wrapper) {
    gradleVersion = '2.0'
}

apply plugin: 'java'

task filter(type: Copy) {
    def subdir = new File(project.buildDir, "subdir")
    println("subdir: "+subdir)

    if( !subdir.exists() ) {
        println("creating subdir")

        if(subdir.mkdirs()) {
            println("succeeded in making folder")

            if(subdir.exists()) {
                println("folder exists")
            } else {
                println("folder does not exist")
            }
        } else {
            println("failed to make folder")
        }
    } else {
        println("folder exists already")
    }
}

After downloading the wrapper using gradle wrapper I then run:

/tmp/test $ ./gradlew clean filter
subdir: /tmp/test/build/subdir
creating subdir
succeeded in making folder
folder exists
:clean
:filter UP-TO-DATE

BUILD SUCCESSFUL

Total time: 4.121 secs

Which seems to indicate everything went okay. However, when I double check I get this:

/tmp/test $ ls -l /tmp/test/build/subdir
ls: /tmp/test/build/subdir: No such file or directory

Notes:

This is on MacOS Mavericks.
The executing user is able to create the directory at the shell.
There is sufficient disk space.

Please advise what I might be doing wrong here with Gradle that fails to create the directory, but that Gradle indicates it was successful? Any troubleshooting tips would be appreciated.

Thanks!

Might be the copy task has done nothing, is "UP-TO-DATE".

13:21:40.045 [INFO] [org.gradle.api.internal.tasks.execution.SkipEmptySourceFile
sTaskExecuter] Skipping task ':filter' as it has no source files.

I think this is due to a Copy task requires a from and into.

Try creating a non copy task like,

task filter() << {
    def subdir = new File(project.buildDir, "subdir")
    println("subdir: "+subdir)

    if( !subdir.exists() ) {
        println("creating subdir")

        if(subdir.mkdirs()) {
            println("succeeded in making folder")

            if(subdir.exists()) {
                println("folder exists")
            } else {
                println("folder does not exist")
            }
        } else {
            println("failed to make folder")
        }
    } else {
        println("folder exists already")
    }
}