How to test d3.js with mocha.js?

@addison 

Testing d3.js with mocha.js involves setting up a testing environment, writing test cases, and running the tests using the Mocha test runner. Here is a step-by-step guide on how to test d3.js with mocha.js:

1. Install Mocha and Chai (a popular assertion library) as dev dependencies in your project directory:

1

npm install --save-dev mocha chai

1. Create a new test file (e.g., d3.test.js) in your project directory and require Mocha and Chai at the top of the file:

1
2

const chai = require('chai');
const expect = chai.expect;

1. Require d3.js in your test file so that you can test its functions:

1

const d3 = require('d3');

1. Write test cases for the d3.js functions that you want to test. For example, if you want to test the d3.max() function, you can write a test case like this:

1
2
3
4
5
6
7

describe('d3.max()', function() {
  it('should return the maximum value in an array', function() {
    const data = [5, 10, 3, 1, 8];
    const max = d3.max(data);
    expect(max).to.equal(10);
  });
});

1. Run the tests using the Mocha test runner by running the following command in your project directory:

1

npx mocha d3.test.js

1. If the tests pass, you will see output indicating that all tests have passed. If any tests fail, you will see output indicating which test(s) failed and why.

By following these steps, you can test d3.js functions using Mocha.js and ensure that your code works as expected.