Brn.FluentBuilder 2.0.0

FluentBuilder

Library for dynamic creation of objects, implemented with a focus on writing more readable and less fragile unit tests.

Available at NuGet

Install-Package Brn.FluentBuilder

Compatibility

.Net 8

Features

1. Public API

1.1. New

Creates a new FluentBuilder instance and starts the fluent construction of the destination object (see next sections).

1.2. With

Allows setting values for writable properties (ie. properties must have 'set' with any kind of modifier):

var newAddress = FluentBuilder<Address>
                .New()
                .With(a => a.Street, "1st Street")
                .With(a => a.ZipCode, "1011")
                .Build();

1.3. WithValue

Allows setting a value (reference type) just passing its instance. FluentBuilder will find the corresponding member to receive the instance based on naming convention:

var newCustomer = FluentBuilder<Customer>
                  .New()
                  .WithValue(FluentBuilder<Address>.New().Build())
                  .Build();

For code above succeed, Customer class must have a property or field named 'Address' or 'address' and being of the same type of Address (or a base class of Address).

1.4. WithDependency

Allows setting values for a injected dependency stored in a private field. This option allows creating a builder for a service that has dependencies and passing a test double object to the SUT.

Sample 1 (Using a concrete dependency for integration tests):

var concreteDependency = new SampleConcreteDependency();
var service = FluentBuilder<SampleServiceWithDependency>
              .New()
              .WithDependency<IDependency, SampleConcreteDependency>(concreteDependency)
              .Build();
    
service.DoSomething();
......

Sample 2 (Using a mock for unit tests): Using Moq, but you can use another mocking library or manually implement your mock object.

var dependencyMock = new Mock<IDependency>();
var service = FluentBuilder<SampleServiceWithDependency>
              .New()
              .WithDependency<IDependency, IDependency>(dependencyMock.Object)
              .Build();
    
service.DoSomething();

dependencyMock.Verify(dependency => dependency.Do(), Times.Once);
......

1.5. AddingTo

Allows setting elements in a collection, one by one:

var customer = FluentBuilder<Customer>
              .New()
              .AddingTo(c => c.Addresses, new Address("1st Street"))
              .AddingTo(c => c.Addresses, new Address("2nd Street"))
              .Build();

Or:

var customer = FluentBuilder<Customer>
              .New()
              .AddingTo(c => c.Addresses, FluentBuilder<Address>.New().With(a => a.Street, "1st Street").Build())
              .AddingTo(c => c.Addresses, FluentBuilder<Address>.New().With(a => a.Street, "2nd Street").Build())
              .Build();

The collection must be a read-only collection with a backing private field. If the collection is a writable property then you can set the whole collection using "With()".

1.6. Build

Constructs and returns the expected object.

1.7. AsList

Like Build() method, with the difference that AsList() builds and returns the object within a list:

IEnumerable<Address> addresses = FluentBuilder<Address>
                                .New()
                                .With(a => a.Street, "1st Street")
                                .AsList();

It's helpful when just one object is necessary for the test but the method/construtor of the SUT requires a collection of objects of that type.

2. Implicit conversion

Allows calling Build() to be avoided since you use the returned type explicitly instead of 'var':

Address address = FluentBuilder<Address>.New().With(a => a.Street, "1st Street");