Test SpringBootApplication in Spock

RestApp.groovy

package com.rest.app

import org.springframework.boot.SpringApplication
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.context.annotation.ComponentScan

@SpringBootApplication
@ComponentScan(["com.rest"])
class RestApp {

    static void main(String[] args) {
        SpringApplication.run(RestApp, args)
    }
}

RestAppTest.groovy

package com.rest.app

import org.springframework.beans.factory.annotation.Autowired
import org.springframework.boot.test.context.SpringBootTest
import org.springframework.context.ApplicationContext
import spock.lang.Specification

@SpringBootTest
class RestAppTest extends Specification {

    @Autowired
    ApplicationContext applicationContext

    def "Boots up without error"() {
        expect:
        applicationContext
    }

    def "App bean is present in application context and app is runnable"() {
        when:
        RestApp app = applicationContext.getBean("restApp")
        app.main([] as String[])

        then:
        noExceptionThrown()
    }
}

Another approach: https://github.com/tomaslin/gs-spring-boot-spock/blob/master/src/test/groovy/hello/HelloControllerSpec.groovy