PosInformatique.FluentAssertions.Json 1.0.4

PosInformatique.FluentAssertions.Json

PosInformatique.FluentAssertions.Json is a library to assert JSON serialization using the Fluent Assertions library style coding.

Installing from NuGet

The PosInformatique.FluentAssertions.Json library is available directly on the official website.

To download and install the library to your Visual Studio unit test projects use the following NuGet command line

Install-Package PosInformatique.FluentAssertions.Json

How it is work?

Imagine that you have the following JSON class:

public class Customer
{
    [JsonPropertyName("id")]
    [JsonPropertyOrder(1)]
    public int Id { get; set; }

    [JsonPropertyName("name")]
    [JsonPropertyOrder(2)]
    public string Name { get; set; }
}

With the following instance:

var customer = new Customer()
{
    Id = 1234,
    Name = "Gilles TOURREAU",
};

You would like to check this class is serializable into the following JSON object:

{
    "id": 1234,
    "name": "Gilles TOURREAU",
}

Using standard assertions you should write the following code 😨:

[Fact]
public void Serialization()
{
    var customer = new Customer()
    {
        Id = 1234,
        Name = "Gilles TOURREAU",
    };

    var json = JsonSerializer.Serialize(customer);

    json.Should().Be("{\"id\":1234,\"name\":\"Gilles TOURREAU\"}");
    
    // Or
    json.Should().Be(@"{""id"":1234,""name"":""Gilles TOURREAU""}");
}

With the following kind of exception when the unit test is incorrect:

As you can see the previous code is not sexy to read (and to write!) and the exception is hard to understand...

Test the serialization of a .NET Object to a JSON object.

With the new fluent style using this library you can write previous unit test like that:

[Fact]
public void Serialization()
{
    var customer = new Customer()
    {
        Id = 1234,
        Name = "Gilles TOURREAU",
    };

    customer.Should().BeJsonSerializableInto(new
    {
        id = 1234,
        name = "Gilles TOURREAU",
    });
}

And when an exception is occured, the exception message contains the JSON path of the property which is error:

Test the deserialization of a JSON object to a .NET Object

You can in the same way test the deserialization JSON object into a .NET object.

[Fact]
public void Deserialization()
{
    var json = new
    {
        id = 1234,
        name = "Gilles TOURREAU",
    };

    json.Should().BeJsonDeserializableInto(new Customer()
    {
        Id = 1234,
        Name = "Gilles TOURREAU",
    });
}

Library dependencies

• The PosInformatique.FluentAssertions.Json library target the .NET Standard 2.0 and can be used with various of .NET architecture (.NET Core, .NET Framework,...).

• The PosInformatique.FluentAssertions.Json library use the 5.0.0 version of the System.Text.Json NuGet package and can be used with old projects that target this library version and earlier.