// See description of this fiddle in blog post:

// https://medium.com/entech-solutions/generate-realistic-test-data-in-net-with-interactive-examples-33343c543a68

​

using System;

using System.Text.Json;

​

using System.Collections.Generic;

​

using Bogus;

public class Program

{

    public static void Main()

    {

        TestBuildDefault();

        TestBuildPassFirstNameAndLastName();

        TestBuildOld();

        TestBuildYoung();

    }

    public static void TestBuildDefault()

    {

        Utils.WriteTitle("EmployeeBuilder.Build Default");

        var employee = new EmployeeBuilder().Build();

        Utils.WriteJson(employee);

    }

    public static void TestBuildPassFirstNameAndLastName()

    {

        Utils.WriteTitle("EmployeeBuilder.Build Default");

        var employee = new EmployeeBuilder()

                        .Customize(f => f.RuleFor(p => p.FirstName, f => "TestFirstName"))

                        .Customize(f => f.RuleFor(p => p.LastName, f => "TestLastName"))

                        .Build();                       

        Utils.WriteJson(employee);

    }

    public static void TestBuildOld()

    {

        Utils.WriteTitle("EmployeeBuilder.Build Old");

        var employee = new EmployeeBuilder()

                        .Old()

                        .Build();                       

        Utils.WriteJson(employee);

    }

    public static void TestBuildYoung()

    {

        Utils.WriteTitle("EmployeeBuilder.Build Young");

        var employee = new EmployeeBuilder()

                        .Young()

                        .Build();                       

        Utils.WriteJson(employee);

    }

}

​

​

public abstract class BuilderBase<TEntity>

       where TEntity : class

{

    protected Faker<TEntity> Faker = new();

​

    public BuilderBase<TEntity> Customize(Action<Faker<TEntity>> action)

    {

        action(Faker);

        return this;

    }   

    public TEntity Build() => Faker.Generate();

    public List<TEntity> Build(int count) => Faker.Generate(count);

}

​

​

public class EmployeeBuilder : BuilderBase<Employee>

{

    public EmployeeBuilder()

    {

         Faker

            .RuleFor(p => p.FirstName, f => f.Name.FirstName())

            .RuleFor(p => p.LastName, f => f.Name.LastName())

            .RuleFor(p => p.JobTitle, f => f.Name.JobTitle())

            .RuleFor(p => p.Email, f => f.Internet.Email())

            .RuleFor(p => p.Age, f => f.Random.Int(20, 50));

    }

    public EmployeeBuilder Old()

    {

        Faker

            .RuleFor(p => p.Age, f => f.Random.Int(50, 60));

        return this;

    }

    public EmployeeBuilder Young()

    {

        Faker

            .RuleFor(p => p.Age, f => f.Random.Int(20, 30));

        return this;

    }

}

​

public class Employee

{

    public string FirstName {get; set;}

    public string LastName {get; set;}

    public string JobTitle {get; set;}

    public string Email {get; set;}

    public int Age {get; set;}

}

​

public static class Utils

{

    public static void WriteTitle(string title)

    {

        Console.WriteLine();

        Console.WriteLine();

        Console.WriteLine("====================================");

        Console.WriteLine();

        Console.WriteLine(title);

        Console.WriteLine();

​

    }

    public static void WriteJson(object obj)

    {

        var options = new JsonSerializerOptions { WriteIndented = true};

        var json = JsonSerializer.Serialize(obj, options);

        Console.WriteLine(json);

    }

}