Bat 🦇 - Behavioral API Tester ·

A Gherkin based DSL for testing HTTP APIs via Cucumber.JS.

• Write RESTful/HTTP API tests in plain English.
• Integrates with Open API specs.
• Easily extend with Cucumber.JS.

    Given I am anonymous
    When I send a 'GET' request to '{base}/pets'
    And I add the query string parameters:
        | sort   | desc   |
        | filter | mammal |
    Then I should receive a response with the status 200
    And I should receive a response within 1000ms
    And the response body json path at "$.[1].name" should equal "Rover"

See the step definition reference for a complete list of all the available Given, When and Then steps.

Contents

• Install
• Get started
• Tips
• Extending
• Reference

Install

npm i --save-dev @harver/bat

Get started

1. Install Cucumber.JS:

npm install --save-dev cucumber

2. Create the file features/support/setup.js with the following code:

const {
    setWorldConstructor,
    After, AfterAll, Before, BeforeAll,
    Given, When, Then
} = require('cucumber');
const { registerHooks, World, registerSteps } = require('@harver/bat');

setWorldConstructor(World);

// Allow Bat to hook into your Cucumber dependencty:
registerHooks({ Before, BeforeAll, After, AfterAll });
registerSteps({ Given, Then, When });

3. Write feature files and scenarios

features/some-scenario.feature:

Scenario: Testing Gets
    When I send a 'GET' request to '{base}/pets'
    And I add the query string parameters:
        | sort   | desc |
        | filter | red  |
    Then I should receive a response with the status 200
    And I should receive a response within 1000ms
    And the response body json path at "$.[1].name" should equal "Rover"

See the Steps Reference for documentation on all available steps.

4. Use the Cucumber.JS CLI to run your specs

./node_modules/.bin/cucumber-js

Tips

Use a Postman compatible environment file to define variables:

ENV_FILE=env/uat.json cucumber-js

The env file will look like this:

{
    "values": [
        {
            "key": "base",
            "value": "http://localhost:3000"
        }
    ]
}

You may then reference this variables, in your steps, like so:

When I send a 'GET' request to '{base}/pets'

Integrate with an Open API 3 specification:

API_SPEC_FILE=test/openapi.yaml cucumber-js

An Open API spec can be used in conjunction with provided steps, such as extracting example request bodies or validating responses against their schemas.

Step short forms

Steps are written in a readable English form, but this can seem quite verbose. Therefore most steps have alternative short form. For example:

Scenario: Testing short forms
    When GET '/pets'
    And qs:
        | sort   | desc    |
        | filter | mammal  |
    Then receive status 200
    And within 1000ms
    And json path at "$.[1].name" should equal "Rover"

Adding a latency buffer

If you are using the I should receive a response within {int}ms step on a network connection you expect to be unusually slow, you can add pad the time of all these steps using the LATENCY_BUFFER environment variable:

LATENCY_BUFFER=1000 cucumber-js

This example allows an extra second for all requests to complete.

Extending

Under the hood, Bat uses SuperAgent for making HTTP requests. You can get a new SuperAgent agent without requiring SuperAgent directly as a dependency by calling this.newAgent() within a custom step definition:

const agent = this.newAgent();

Bat also maintains a cache of agents that persists across Cucumber scenarios. This means that if each scenario uses a Given step to set up some authorization, an HTTP session or Bearer token can be reused without needing to re-login every time.

The code example below (taken from the tests), demonstrates a custom Given step for logging in and maintaining a client session:

const { setWorldConstructor, After, AfterAll, Before, BeforeAll, Given, When, Then } = require('cucumber');
const { registerHooks, World, registerSteps } = require('@harver/bat');

setWorldConstructor(World);
registerHooks({ After, AfterAll, Before, BeforeAll });
registerSteps({ Given, Then, When });

// a custom login step
Given('I am logged in as a {string}', async function(role) {
    // does an agent for this role already exist?
    const roleAgent = this.getAgentByRole(role);
    if (roleAgent) {
        this.setAgentByRole(role, roleAgent);
        return;
    }

    // construct and send a login request
    const agent = this.newAgent();
    const req = agent.post(this.replaceVars('{base}/my-login'));

    await req.send({
        // this gets predefined credentials for this role from the `env/dev.json` file
        username: this.replaceVars(`{${role}_user}`),
    });

    // this also sets `this.currentAgent` so this agent will be used
    // for creating the next request.
    this.setAgentByRole(role, agent);
});

See the Cucumber.JS documentation for more information on writing step definitions.

Reference

Steps reference for support writing feature files.

World API for support writing custom step definitions.