6. Write the API consumer

The Consumer

Time to create our consumer code base. For the sake of simplicity, we're going to focus only on the bits of our application that communicate to the provider. In our project, they are:

The model (the Product class), representing the data returned from the Product API: example-bi-directional-consumer-mountebank/src/api.js
The API client (the ProductApiClient) which will be responsible for making the HTTP calls to the Product API and returning an internal representation of an Product: example-bi-directional-consumer-mountebank/src/product.js

Install the dependencies for the project: npm i

Product Model

src/product.js

export class Product {
  constructor({id, name, type}) {
    if (!id || !name || !type) {
      throw Error("id, name and type are required properties")
    }
    this.id = id
    this.name = name
    this.type = type
  }
}

See full example on GitHub

Product API Client

Here is a version of our API client code. This code is responsible for fetching products from the API, and returning a Product:

src/api.js

const axios = require("axios");
const adapter = require("axios/lib/adapters/http");
const { Product } = require("./product");

axios.defaults.adapter = adapter;

export class ProductAPIClient {
  constructor(url) {
    if (url === undefined || url === "") {
      url = process.env.BASE_URL;
    }
    if (url.endsWith("/")) {
      url = url.substr(0, url.length - 1);
    }
    this.url = url;
  }

  withPath(path) {
    if (!path.startsWith("/")) {
      path = "/" + path;
    }
    return `${this.url}${path}`;
  }

  async getAllProducts() {
    return axios
      .get(this.withPath("/products"))
      .then((r) => r.data.map((p) => new Product(p)));
  }

  async getProduct(id) {
    return axios
      .get(this.withPath("/product/" + id))
      .then((r) => new Product(r.data));
  }
}

See full example on GitHub

This class, and specifically the getProduct() and getAllProducts methods, will be the target of our contract tests.

You can pick your consumer now from the Examples page.

Fork and clone the consumer

Fork the example-bi-directional-consumer-mountebank project in to your own Github account (click the 'Fork' button in the top right).

Clone the repositories on to your local machine.

git clone [email protected]:<YOUR_GITHUB_USERNAME>/example-bi-directional-consumer-mountebank.git

Install the dependencies.
```
npm install
```

Check

Before moving to the next step, check the following:

You are in the correct directory cd /root/example-bi-directional-consumer-mountebank
You have run npm i and the dependencies have been installed
You have studied and understood the Product class: example-bi-directional-consumer-mountebank/src/product.js
You have studied and understood the API client: example-bi-directional-consumer-mountebank/src/api.js

In this section: