In a Spock specification we write our assertion in the then: or expect: blocks. If we need to write multiple assertions for an object we can group those with the with method. We specify the object we want write assertions for as argument followed by a closure with the real assertions. We don't need to use the assert keyword inside the closure, just as we don't have to use the assert keyword in an expect: or then: block.

In the following example specification we have a very simple implementation for finding an User object. We want to check that the properties username and name have the correct value.

@Grab("org.spockframework:spock-core:1.0-groovy-2.4")
import spock.lang.Specification
import spock.lang.Subject

class UserServiceSpec extends Specification {

    @Subject
    private UserService userService = new DefaultUserService()

    def "check user properties"() {
        when:
        final User user = userService.findUser("mrhaki")

        then:
        // Assert each property.
        user.username == "mrhaki"
        user.name == "Hubert A. Klein Ikkink"
    }

    def "check user properties using with()"() {
        when:
        final User user = userService.findUser("mrhaki")

        then:
        // Assert using with().
        with(user) {
            username == "mrhaki"
            name == "Hubert A. Klein Ikkink"
        }
    }

    def "check expected user properties using with()"() {
        expect:
        with(userService.findUser("mrhaki")) {
            username == "mrhaki"
            name == "Hubert A. Klein Ikkink"
        }
    }
}

interface UserService {
    User findUser(final String username)
}

class DefaultUserService implements UserService {
    User findUser(final String username) {
        new User(username: "mrhaki", name: "Hubert A. Klein Ikkink")
    }
}

class User {
    String username
    String name
}

Written with Spock 1.0.

Original blog post