How can I test for Groovy constructors in Spock Unit test with 100% code coverage

My question is: I am new to Spock testing, and am trying to get 100% code coverage on this User Class. To get me started, can someone help me figure out how to test the constructor. What I currently have is not covering it using the cobertura plugin. Also, if someone is knowledgeable about Spock + Cobertura, maybe you could shed some light on what I'm doing wrong, and some pointers for further testing.

I have a class that represents a user:

import java.io.Serializable;
import java.util.Set;

class User implements Serializable {
    String email
    byte[] photo

    static hasMany = [lineups: Lineup]

    private static final long serialVersionUID = 1

    transient springSecurityService

    String username
    String password
    boolean enabled = true
    boolean accountExpired
    boolean accountLocked
    boolean passwordExpired

    User(String username, String password) {
        this()
        this.username = username
        this.password = password
    }

    @Override
    int hashCode() {
        username?.hashCode() ?: 0
    }

    @Override
    boolean equals(other) {
        is(other) || (other instanceof User && other.username == username)
    }


    Set<SecRole> getAuthorities() {
        SecUserSecRole.findAllBySecUser(this)*.secRole
    }

    def beforeInsert() {
        encodePassword()
    }

    def beforeUpdate() {
        if (isDirty('password')) {
            encodePassword()
        }
    }

    protected void encodePassword() {
        password = springSecurityService?.passwordEncoder ? springSecurityService.encodePassword(password) : password
    }

    static transients = ['springSecurityService']

    static constraints = {
        username blank: false, unique: true
        password blank: false

        email(unique: true, blank: false, nullable: true)  // needs to be moved to account
        photo(nullable:true, maxSize: 1024 * 1024 * 2 /* 2MB */)
    }

    static mapping = {
        password column: '`password`'
    }

    String toString() {
        return id + ": " + email + " " + username
    }
}

Then I have a Spock Unit Test: (not all my code is here, but just for the examples that I'm requesting info on...

@TestFor(User)
class UserSpec extends Specification {
    User user

    def setup() {
        user = new User(
            username: "fredflintstone",
            password: "Wilma1",
            enabled: true).save(failOnError: true, flush: true)

    }

    def cleanup() {
        user = null
    }

    // Constructor tests
    void "test to check constructor works"() {
        when:
        mockForConstraintsTests(User, [user])

        expect:
        user.validate()
        user != null
        user.username != null
        user.password != null
    }

    void "test #hashCode works"() {
        setup:

        mockForConstraintsTests(User, [user])

        expect:
        user.username.hashCode() != null

    }

}