[Spock] Pancoc characterization test 1

HeaderSpec.groovy

import spock.lang.Specification

class HeaderSpec extends Specification {
    def "header characterization test"() {
        when:
        def proc = "pandoc header.md -o header.html".execute()
        proc.waitFor()
        then:
        def result = new File("header.html").getText('UTF-8')
        "" == result
    }
}