Customizing a specific string inside a class using AutoFixture
Full source code.
I’ve been using AutoFixture for a while with my unit tests. It creates objects with prefilled data, saving me the hassle of manually constructing them.
Basic usage
If you want a string from AutoFixture do something like -
string myString = fixture.Create();"c2eefff9-9cc2-4358-aee1-2d27b0476e41"If you want to prefix the string do this -
string myPrefixedString = fixture.Create("Prefix");"Prefix191dd4bc-f3ed-4d19-ac36-f3c84c958155"If you want something that looks like an email address -
string emailAddress = fixture.Create().Address;"9ed7e16b-f6df-42d6-8812-d7ea6580f300@example.org"Where it starts to get a bit tricky is if you have a class like this -
public class Account
{
public Guid AccountId { get; set; }
public string Firstname { get; set; }
public string Lastname { get; set; }
public IEnumerable<string> EmailAddresses { get; set; }
}Because I am using a string to represent an email address AutoFixture will give me a string, not an email address.
Here are two solutions.
Solution 1
fixture.Customize<Account>(c => c.With(a => a.EmailAddresses, fixture.CreateMany<MailAddress>().Select(ma => ma.Address.ToString())));f45a37ae-6d2c-42a5-92ac-832e6ea2d028@example.net
72625222-e7af-4c29-96ed-4219efc1a859@example.net
54a39694-fd7a-458c-8739-0667ec9fa2d7@example.netSolution 2
If I want to generate email address that look a little more like real world address I have to create a SpecimenBuilder.
1 public class EmailAddressesStringSpecimenBuilder : ISpecimenBuilder
2 {
3 public object Create(object request, ISpecimenContext context)
4 {
5 var propertyInfo = request as PropertyInfo;
6
7 if (propertyInfo != null)
8 {
9 if (propertyInfo.Name == "EmailAddresses" && propertyInfo.PropertyType == typeof (IEnumerable<string>))
10 {
11 // of course you can customize how the mail addresses are created, you can even use a fixture to create strings :)
12 IEnumerable<string> emailAddresses = new List<string>() {"user1@acme.com", "user2@unknown.com", "user3@nothing.com"};
13 return emailAddresses;
14 }
15 }
16 return new NoSpecimen();
17 }
18 }How to use the customizations
1 Fixture fixture = new Fixture();
2
3 fixture.Customizations.Add(new EmailAddressesStringSpecimenBuilder());
4 // use one of the two customizations here, but not both
5 // fixture.Customize<Account>(c => c.With(a => a.EmailAddresses, fixture.CreateMany<MailAddress>().Select(ma => ma.Address.ToString())));
6
7 var account1 = fixture.Create<Account>();
8 var account2 = fixture.Create<Account>();Full source code.