gradle testing plugin with spock

Given:
gradle version is 2.2.1

Task example:
<code>
class TestTask extends DefaultTask {
    PegDownProcessor markdown =  new PegDownProcessor(Extensions.ALL);

    @TaskAction
    private void generateDocs() {
        String str = markdown.markdownToHtml '##Hello'
        println str
    }
}
</code>
I have written task like that and added by plugin. Plugin just adds task with 
some name with current type of task.
<code>
    void apply(Project project) {
        project.tasks.create('generateDocs', TestTask)
    }
</code>
When have I written test with JUnit all was fine but when I have tried to use 
spock, I had a lot of problem.

dependncies for spock in buildSRC:
<code>
compile gradleApi()
compile localGroovy()
compile group: 'org.pegdown', name: 'pegdown', version: '1.4.2'
testCompile 'org.spockframework:spock-core:0.7-groovy-2.0'
</code>
Doesn't work even with empty spec:
<code>
class TestPluginSpec extends Specification {

}
</code>
and produce next stacktrace:
<code>
com.test.gradle.plugin.TestPluginSpec > initializationError FAILED
    org.spockframework.util.InternalSpockError
        Caused by: java.lang.ExceptionInInitializerError at TestPluginSpec.groovy:-1
            Caused by: groovy.lang.GroovyRuntimeException at TestPluginSpec.groovy:-1
</code>

When I have changed spock version to:
<code>
testCompile 'org.spockframework:spock-core:1.0-groovy-2.3-SNAPSHOT'
</code>
and add repositories:
<code>
repositories{
    maven { url 'http://repo1.maven.org/maven2' }
    maven { url 'http://oss.sonatype.org/content/repositories/snapshots' }
}
</code>
I couldn't instantiate my task and as I understood this problem related to 
pegdown processor instantiation, because for another type of fields(String, 
List<String>) all works fine. I can move `new PegDownProcessor(Extensions.ALL)` 
to method and test will  pass too. As example:
<code>
lass TestTask extends DefaultTask {
    PegDownProcessor markdown

    @TaskAction
    private void generateDocs() {
        markdown =  =  new PegDownProcessor(Extensions.ALL)
        String str = markdown.markdownToHtml '##Hello'
        println str
    }
}
</code>

For both cases Junit and Spock I have used one setup method of tests with body:
<code>
    void setup() {
        project = ProjectBuilder.builder().build()
        project.apply plugin: TestPlugin
    }
</code>

if I use gradle 1.9 and `testCompile 
'org.spockframework:spock-core:0.7-groovy-1.8'` in both cases everything is 
good. So I think this problem depends on version of spock and groovy in gradle. 
Can you help me how I should use spock with gradle version 2.0 and higher?

_**As I have tested this problem related to all version of gradle 2.x** and 
last release candidate gradle 2.3-rc-3**_
Original issue reported on code.google.com by Stavyts...@gmail.com on 9 Feb 2015 at 6:46
sampig / spock

gradle testing plugin with spock #386
