Specmatic Sample: .NET core BFF calling Domain API

• Specmatic Website
• Specmatic Documentation

This sample project demonstrates how we can practice contract-driven development and contract testing in a .NET core (C#) application that depends on an external domain service. Here, Specmatic is used to stub calls to domain API service based on its OpenAPI spec.

Here is the domain api contract/open api spec

Definitions

• BFF: Backend for Front End
• Domain API: API managing the domain model
• Specmatic Stub server: Create a server that can act as a real service using its OpenAPI spec

Background

A typical web application might look like this. We can use Specmatic to practice contract-driven development and test all the components mentioned below. In this sample project, we look at how to do this for .NET core BFF which is dependent on Domain API Service demonstrating OpenAPI support in specmatic.

Tech

1. .NET core
2. Specmatic

Run Tests

This will start the specmatic stub server for domain api using the information in specmatic.yaml and run contract tests using Specmatic.

1. Using Terminal -

     dotnet test

2. Using docker -
   • Start Docker Desktop
   • Run the application dotnet run
   • Navigate to test Project (/specmatic-order-bff-csharp.test)
   • Start the stub Server docker run -v "$PWD/specmatic.yaml:/usr/src/app/specmatic.yaml" -p 8090:9000 znsio/specmatic stub
   • Run the tests docker run --network host -v "$PWD/specmatic.yaml:/usr/src/app/specmatic.yaml" -v "$PWD/build/reports/specmatic:/usr/src/app/build/reports/specmatic" znsio/specmatic test --port=8080 --host=host.docker.internal

Break down each component to understand what is happening

Prerequisites

1. Docker Desktop
2. Dotnet SDK
3. If you are on a Windows OS, please use PowerShell.

Start the dependent components

1. Start domain api stub server

docker run -v "$PWD/specmatic.yaml:/usr/src/app/specmatic.yaml" -p 8090:9000 znsio/specmatic stub

Start BFF Server

This will start the .NET core BFF server

dotnet run

Test if everything is working

Note: For Windows OS, add .exe extension to curl command on PowerShell or use cmd.exe instead.

curl -H "pageSize: 10" "http://localhost:8080/findAvailableProducts"

You result should look like:

[{"id":698,"name":"NUBYR","type":"book","inventory":278}]

Also observe the logs in the Specmatic HTTP Stub Server.