CLI Integration Test Helper

cmd.js

/**
 * Integration test helper
 * Author: Andrés Zorro <[email protected]>
 */

const { existsSync } = require('fs');
const { constants } = require('os');
const spawn = require('cross-spawn');
const concat = require('concat-stream');
const PATH = process.env.PATH;

/**
 * Creates a child process with script path
 * @param {string} processPath Path of the process to execute
 * @param {Array} args Arguments to the command
 * @param {Object} env (optional) Environment variables
 */
function createProcess(processPath, args = [], env = null) {
    // Ensure that path exists
    if (!processPath || !existsSync(processPath)) {
        throw new Error('Invalid process path');
    }

    args = [processPath].concat(args);
    
    // This works for node based CLIs, but can easily be adjusted to
    // any other process installed in the system
    return spawn('node', args, {
        env: Object.assign(
            {
                NODE_ENV: 'test',
                preventAutoStart: false,
                PATH // This is needed in order to get all the binaries in your current terminal
            },
            env
        ),
        stdio: [null, null, null, 'ipc'] // This enables interprocess communication (IPC)
    });
}

/**
 * Creates a command and executes inputs (user responses) to the stdin
 * Returns a promise that resolves when all inputs are sent
 * Rejects the promise if any error
 * @param {string} processPath Path of the process to execute
 * @param {Array} args Arguments to the command
 * @param {Array} inputs (Optional) Array of inputs (user responses)
 * @param {Object} opts (optional) Environment variables
 */
function executeWithInput(processPath, args = [], inputs = [], opts = {}) {
    if (!Array.isArray(inputs)) {
        opts = inputs;
        inputs = [];
    }

    const { env = null, timeout = 100, maxTimeout = 10000 } = opts;
    const childProcess = createProcess(processPath, args, env);
    childProcess.stdin.setEncoding('utf-8');

    let currentInputTimeout, killIOTimeout;
    
    // Creates a loop to feed user inputs to the child process in order to get results from the tool
    // This code is heavily inspired (if not blantantly copied) from inquirer-test:
    // https://github.com/ewnd9/inquirer-test/blob/6e2c40bbd39a061d3e52a8b1ee52cdac88f8d7f7/index.js#L14
    const loop = inputs => {
        if (killIOTimeout) {
            clearTimeout(killIOTimeout);
        }
 
        if (!inputs.length) {
            childProcess.stdin.end();
            
            // Set a timeout to wait for CLI response. If CLI takes longer than
            // maxTimeout to respond, kill the childProcess and notify user
            killIOTimeout = setTimeout(() => {
                console.error('Error: Reached I/O timeout');
                childProcess.kill(constants.signals.SIGTERM);
            }, maxTimeout);
 
            return;
        }

        currentInputTimeout = setTimeout(() => {
            childProcess.stdin.write(inputs[0]);
            // Log debug I/O statements on tests
            if (env && env.DEBUG) {
                console.log('input:', inputs[0]);
            }
            loop(inputs.slice(1));
        }, timeout);
    };

    const promise = new Promise((resolve, reject) => {
        // Get errors from CLI
        childProcess.stderr.on('data', data => {
            // Log debug I/O statements on tests
            if (env && env.DEBUG) {
                console.log('error:', data.toString());
            }
        });
        
        // Get output from CLI
        childProcess.stdout.on('data', data => {
            // Log debug I/O statements on tests
            if (env && env.DEBUG) {
                console.log('output:', data.toString());
            }
        });

        childProcess.stderr.once('data', err => {
            childProcess.stdin.end();

            if (currentInputTimeout) {
                clearTimeout(currentInputTimeout);
                inputs = [];
            }
            reject(err.toString());
        });

        childProcess.on('error', reject);
        
        // Kick off the process
        loop(inputs);

        childProcess.stdout.pipe(
            concat(result => {
                if (killIOTimeout) {
                    clearTimeout(killIOTimeout);
                }

                resolve(result.toString());
            })
        );
    });
    
    // Appending the process to the promise, in order to
    // add additional parameters or behavior (such as IPC communication)
    promise.attachedProcess = childProcess;

    return promise;
}

module.exports = {
    createProcess,
    create: processPath => {
        const fn = (...args) => executeWithInput(processPath, ...args);

        return {
            execute: fn
        };
    },
    DOWN: '\x1B\x5B\x42',
    UP: '\x1B\x5B\x41',
    ENTER: '\x0D',
    SPACE: '\x20'
};