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