Xcepto.NET

Xcepto is a BDD testing framework for distributed systems. Tests are specified declaratively here.

Getting Started

Test specification happens according to the Given-When-Then pattern.

Mental model

Test steps are not immediately executed when called! They are compiled into a state machine, where transition depends on the specified conditions.

The states are linked in a chain:

[Start] -> [First] -> [Second] -> [Third] -> [Final]

The test passes, if the Final state was reached before a timeout.

Given

Xcepto.Given introduces a specification environment based on a scenario.

XceptoTest.Given(scenario, builder =>
{
    // Declare test behaviour here
}

Scenario classes specify instructions to setup and prepare the system under test.

When (Actions)

Actions often require interfacing technologies. Official adapters can be used to integrate some popular ones.

XceptoTest.Given(scenario, builder =>
{
    var rest = builder.RegisterAdapter(new XceptoRestAdapter());

    // When
    rest.PostRequest<SomeRequest, SomeResponse>(
        "localhost:3000/", new SomeRequest(),  
        someReponse => someResponse.value > 1000);
}

Post requests in particular also enable response validation (so they are hybrid action/expectation).

Then (Expectations)

Expectations represent transition conditions.

RabbitMQ can be used to block transition until a certain kind of message is published.

XceptoTest.Given(scenario, builder =>
{
    var rabbitMq = builder.RegisterAdapter(new XceptoRabbitMqAdapter(config));
    
    // When some Action happens
    
    // Then expect a certain response
    rabbitMq.EventCondition<ResponseMessage>(
        e => e.someValue == 1234);
}

Full example

Expect that the backend message bus publishes Search(Component)SearchedForArticle whenever the client initiates a Process with a SearchForArticleRequest.

[Test]
public async Task Test()
{
    // Arrange
    var config = CustomRabbitMqConfig.GetRabbitMqConfig();
    var searchForArticleRequest = new SearchForArticleRequest
    {
        ArticleName = "Christmas Tree"
    };
    SearchForArticleRoute articleRoute = new SearchForArticleRoute();
    var postUrl = new Uri($"http://localhost:8080/{articleRoute.Path}");
    
    await XceptoTest.Given(new ChristmasGiftsScenario(), builder =>
    {
        var rest = builder.RegisterAdapter(new XceptoRestAdapter());
        var rabbitMq = builder.RegisterAdapter(new XceptoRabbitMqAdapter(config));
    
        // When
        rest.PostRequest<SearchForArticleRequest, SearchForArticleResponse>(
            postUrl, searchForArticleRequest,  _ => true);
        
        // Then
        rabbitMq.EventCondition<SearchSearchedForArticle>(
            e => e.ArticleName == searchForArticleRequest.ArticleName);
    });
}

Here, ChristmasGiftsScenario starts the production environment using docker compose. The message bus also has to be configured, GetRabbitMqConfig returns a configuration that describes the exchanges, queues and keys and references the docker container as a host.

Adapters

Xcepto supports several technologies through adapters.

Core library:

• Xcepto

Adapters:

• Xcepto.RabbitMQ (listening for messages)
• Xcepto.REST (sending POST requests, validating POST responses)