EUnit

<dependency>
    <groupId>com.github.ofofs</groupId>
    <artifactId>eunit</artifactId>
    <version>${eunit.version}</version>
</dependency>

package com.github.ofofs.eunit.test.model;

import com.github.ofofs.eunit.annotation.Rule;


/**
 * @author kangyonggan
 * @since 2018/7/21 0021
 */
public class User {

    private Long id;

    @Rule(minLength = 5, maxLength = 20)
    private String username;

    private String password;

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }

}

package com.github.ofofs.eunit.test;

import com.github.ofofs.eunit.DataFactory;
import com.github.ofofs.eunit.test.model.User;

/**
 * @author kangyonggan
 * @since 2018/7/21 0021
 */
public class UserSimpleTest {

    public static void main(String[] args) {
        User user = DataFactory.instance(User.class);
        System.out.println(user);
    }

}

User{id=8462870299209684556, username='kolH4D8roMdK2Kpnq', password='Xace7HK'}