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Stubbr: A simple request stub provider for ASP.NET Core

Fanie Reynders

Sep 28, 2016 • 2 min read

Building back-end services sometimes require stubbing of stuff. Stubbr is middleware for ASP.NET Core that provide stubs from a given pre-defined request endpoints configuration.

Stubs can be sourced from local disk or a remote location. The stub configuration system is built on top of ASP.NET Core's configuration model, having support for JSON, XML and INI files out of the box.

Installing

Stubbr can be installed from Nuget using the following command:

Install-Package Stubbr

Or you can also manually add Stubbr to the project.json file

{
  "dependencies": {
     "Stubbr": "0.0.1"
  }
}

Usage

Using Stubbr should be easy and simple. All it requires is some configuration about the request and details on the response that must be provided. Given the following configuration within mystubs-config.json:

{
  "Stubs": {
    "GET /foo/bar": {
      "Headers": {
        "X-Header-1": "X-Header-1-Value",
        "Content-Type": "application/json"
      },
      "Body": "./stubs/response1.json",
      "Status": 200
    },
    "POST /api/foo/bar/baz": {
      "Headers": {
        "X-Header-3": "X-Header-3-Value",
        "Content-Type": "application/xml"
      },
      "Body": "./stubs/response2.xml",
      "Status": 201
    }
  }
}

Note that the Body can be a remote URI as well.

Simply load the configuration into the configuration system of ASP.NET Core:

public Startup(IHostingEnvironment env)  
{
  var builder = new ConfigurationBuilder()

  //...
  builder.AddJsonFile("stubs.config.json");

  Configuration = builder.Build();
}

public IConfigurationRoot Configuration { get; }

Following the Add/Use convention pattern in ASP.NET Core, we add Stubbr to the IServiceCollection, passing in the configuration section and then registering it within the pipeline:

public void ConfigureServices(IServiceCollection services)  
{
  services.AddStubs(Configuration.GetSection("Stubs"));
}

public void Configure(IApplicationBuilder app)  
{
  app.UseStubs();
}

Thats it - now when you request these configured endpoints, the stub responses will be returned.

Configuration in your formats

Because Stubbr works with the built-in configuration system of ASP.NET Core, it automatically supports configurations sourced from various formats like JSON, XML, INI, CLI and even in-memory key/value pairs.

Here's an example of Stubbr configuration in XML:

<?xml version="1.0" encoding="UTF-8" ?>  
<config>  
  <Stubs Name="GET /api/people">
    <Headers>
      <Content-Type>application/json</Content-Type>
    </Headers>
    <Body>./stubs/people-sample.json</Body>
    <Status>200</Status>
  </Stubs>
</config>

and INI - don't know why you'd want this, but you can have it :)

[Stubs]
GET /api/cool/image:Headers:Content-Type=image/png  
GET /api/cool/image:Body=./stubs/sample.png  
GET /api/cool/image:Status=200

The source code for this little project is available on my Github so please go and try it out.

Please give me some feedback, your comments or ideas are important.

Till next time