McVerifier 1.0.3

Microservices message contract verifier .net

This is verification contract library. It provides implementations that make it possible to run Message contract testing in event-driven microservice architecture.

• It verify message schema and prevent unexpected changes.
• It verify producer message using concumers contracts.

Why Use This Library?

• It removes dependencies between microservices while using asynchronous events communication and keep contracts consistence.
• Not need to use shared nuget packages or git submodules with message types which bring dependencies between microservices.
• You can be sure that your messages contracts valid between microservices.
• You notified about the issue during pipelines run and not after you update a nuget package.

How it works

<img src="https://github.com/khdevnet/mc-verifier/blob/master/docs/how-it-workds.png" width="550">

Getting started

Consumer project

• Install the NJsonSchema nuget package
• Create message and add constraints

public class UserCreatedEvent
{
    [Required]
    [Range(0, 10)]
    public int? Id { get; set; }
}

Consumer contracts verification project

• Create a new Xunit test project Consumer1.ContractTests example
• Install the McVerifier nuget package
• Install the ApprovalTests nuget package
• Create test class

using ApprovalTests.Namers;
using ApprovalTests.Reporters;
using McVerifier;
using McVerifier.Utils;
using System.IO;
using Xunit;

namespace Consumer1.ContractTests;

[UseApprovalSubdirectory("Approvals")]
[UseReporter(typeof(VisualStudioReporter))]
public class Schemas
{
    [Fact]
    public void UserCreatedEvent()
    {
        // Folder where generated json schema contract file will be save.
        var contractsFolder = Path.Combine(
            FileUtils.GetSolutionDirectory(),
            "ConsumerContracts//Consumer1");

        MessageSchema
            .Create(typeof(UserCreatedEvent))
            .Verify() // Verify message json schema using ApprovalTests
            .Save(contractsFolder); // if verification successful then save schema
    }
}

Producer project

• Install the NJsonSchema nuget package
• Create message and add constraints

public class UserCreatedEvent
{
    [Required]
    [Range(0, 10)]
    public int Id { get; set; }

    [Required]
    public string Name { get; set; } = string.Empty;

    [Required]
    [Range(0, 10)]
    public decimal Price { get; set; }
}

Producer contracts verification project

• Create a new Xunit test project Producer.ContractTests example
• Install the McVerifier nuget package
• Install the ApprovalTests nuget package
• Create test class

using McVerifier;
using McVerifier.Abstractions.Loggers;
using McVerifier.Utils;
using System.IO;
using System.Threading.Tasks;
using Xunit;
using Xunit.Abstractions;

namespace Producer.ContractTests;

public class ProducerContracts
{
    private const string ConsumerContracts = "ConsumerContracts";
    private readonly ITestOutputHelper _logger;

    public ProducerContracts(ITestOutputHelper logger)
        => _logger = logger;

    [Fact]
    public async Task Verify()
    {
        // Consumers message contracts root folder
        var messagesSchemaRootFolder = Path.Combine(
            FileUtils.GetSolutionDirectory(),
            ConsumerContracts);

        // verify producer message types using consumers contracts
        await MessageTypesApprovals
            .Create(new SchemaVerifierTestOutputLogger(_logger))
            .Verify(messagesSchemaRootFolder, "^Producer.*Event$", "^Producer.*Command$");
    }
}

public class SchemaVerifierTestOutputLogger : IMessageVerifierTestOutputLogger
{
    private readonly ITestOutputHelper _logger;

    public SchemaVerifierTestOutputLogger(ITestOutputHelper logger)
        => _logger = logger;

    public void Log(string message) => _logger.WriteLine(message);
}

How to run example

• Run Consumer1.ContractTests and Consumer2.ContractTests
• Contracts will be save to ConsumerContracts folder
• Run Producer.ContractTests