mock-cli

CLI capture tool for testing command-line apps

Overview

This tool allows you to simulate a separate command-line environment within the current process, automatically capturing any input/output for the simulated process. It works by temporarily faking process.argv and stdio (and optionally redirecting stdio), so your CLI app code has no idea it is actually being run in a test environment.

process.exit() and uncaught errors are handled gracefully, returning the process exit code and the captured stdio contents.

Example

var mockCli = require('mock-cli');
var assert = require('assert');
 
var argv = ['node', 'hello-world-app.js', '--foo', 'bar']; // Fake argv
var stdio = {
    stdin: require('./mocks/fakeInputStream'), // Hook up a fake input stream
    stdout: process.stdout, // Display the captured output in the main console
    stderr: process.stderr // Display the captured error output in the main console
};
var kill = mockCli(argv, stdio, function onProcessComplete(error, result) {
    var exitCode = result.code; // Process exit code
    var stdout = result.stdout; // UTF-8 string contents of process.stdout
    var stderr = result.stderr; // UTF-8 string contents of process.stderr
 
    assert.equal(exitCode, 0);
    assert.equal(stdout, 'Hello, world!\n');
    assert.equal(stderr, '');
});
 
// Execute the CLI task
require('./bin/hello-world-app');
 
// Kill the task if still running after one second
setTimeout(kill, 1000);

Usage

mockCli(argv, stdio, exitCallback)

Simulate a separate command-line environment within the current process

Arguments:

Name	Type	Required	Default	Description
argv	Array	No	process.argv	Fake argv for the simulated process
stdio	object	No	null	Object containing streams that are used to fake stdio
stdio.stdin	Stream	No	null	Input stream that is piped into the simulated process as process.stdin
stdio.stdout	Stream	No	null	Output stream that is connected to process.stdout of the simulated process
stdio.stderr	Stream	No	null	Error stream that is connected to process.stderr of the simulated process
errorCallback	function	No	null	Callback that is invoked once the simulated process completes or throws an uncaught exception

• errorCallback has the following signature:

  ##### function(error, result)

  ###### Arguments:

  Name	Type	Description
  error	Error	Uncaught exception thrown by the simulated process
  result	object	Object containing information about the simulated process
  result.code	number	Process exit code, or 1 on an uncaught exception
  result.stdin	string	UTF-8 contents of process.stdin, captured during simulation
  result.stdout	string	UTF-8 contents of process.stdout, captured during simulation
  result.stderr	string	UTF-8 contents of process.stderr, captured during simulation

Returns:

function Function that kills the simulated process (as if the user pressed Ctrl+C).

• This function returns a results object, as seen in exitCallback arguments.