Unroll It

Simple helper function for writing data-driven / parametrized unit tests in Mocha.

Introduction

Mocha does not have explicit support writing parametrized tests. Instead it suggests using imperative code to dynamically generate test cases.

This module provides a helper function which is a wrapper around the it() function for declaratively creating data-driven tests. The end result is the same as in the example in Mocha's documentation but the code is shorter and hopefully easier to read. My experience has been that having an explicit method for creating data-driven tests tends to promote their use in a codebase.

Installation

npm install unroll-it

Usage

unroll-it exports a function that is used in place of the "it" function to create a test which is run once for each case in an array of test cases. The syntax is:

unroll(description, testFunction, testCases);

Each test case is an object which is passed to the testFunction. The properties in the test case may also be referenced in the description.

Here is a simple synchronous test:

var unroll = require('unroll-it');
 
describe('upperCase', () => {
  unroll('should return #output given #input', (testCase) => {
    assert.equal(upperCase(testCase.input), testCase.output);
  },[{
    input: 'john',
    output: 'JOHN',
  },{
    input: 'mark',
    output: 'MARK',
  }]);
});

The "#output" and "#input" placeholders will be replaced with the corresponding values from the test case.

Asynchronous tests

Similar to the it() function in Mocha, asynchronous tests can be written either by returning a Promise from the test function or by accepting a done() callback as the first argument to the test function which is called when the test completes.