CLI Integration Test Helper

cmd.js

/**
 * Integration test helper
 * Author: Andrés Zorro <zorrodg@gmail.com>
 */

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'
};

LICENSE

MIT License
Copyright © 2019 Andrés Zorro

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

Thought I'd share a snippet that I've used in my tests. It's a bit shorter and uses output from stdout to trigger processing of the next batch of inputs. I ran the utility without setTimeout and it worked even for consecutive input operations. setTimeout is still used, but more as a precaution with a time buffer of just 5 milliseconds. Realistic interactive CLI tests are slower than normal and using very short timeouts speeds things up.

https://github.com/aptivator/anagrammer/blob/master/test/_lib/cli.js