mock-stdin

What is mock-stdin?

The mock-stdin npm package is used to mock the standard input (stdin) stream in Node.js applications. This is particularly useful for testing command-line applications where user input is required.

What are mock-stdin's main functionalities?

Mocking stdin input

This feature allows you to simulate user input by sending data to the stdin stream. The example demonstrates how to send 'input data' to stdin and then end the input stream.

const mockStdin = require('mock-stdin').stdin();

// Start mocking stdin
mockStdin.send('input data\n');
mockStdin.end();

// Your application code that reads from stdin
process.stdin.on('data', (data) => {
  console.log(`Received: ${data}`);
});

Pausing and resuming stdin

This feature allows you to pause and resume the stdin stream. The example shows how to send 'input data' to stdin, pause the stream, and then resume it.

const mockStdin = require('mock-stdin').stdin();

// Start mocking stdin
mockStdin.send('input data\n');
mockStdin.pause();

// Your application code that reads from stdin
process.stdin.on('data', (data) => {
  console.log(`Received: ${data}`);
});

// Resume stdin
mockStdin.resume();

Flushing stdin

This feature allows you to flush the stdin stream, ensuring that all data sent to stdin is processed immediately. The example demonstrates how to send 'input data' to stdin and then flush the stream.

const mockStdin = require('mock-stdin').stdin();

// Start mocking stdin
mockStdin.send('input data\n');
mockStdin.flush();

// Your application code that reads from stdin
process.stdin.on('data', (data) => {
  console.log(`Received: ${data}`);
});

Other packages similar to mock-stdin

mock-stdio

The mock-stdio package provides similar functionality to mock-stdin but also includes support for mocking stdout and stderr. This makes it a more comprehensive solution for testing command-line applications.

sinon

Sinon is a popular testing library that provides standalone test spies, stubs, and mocks for JavaScript. While it is not specifically designed for mocking stdin, it can be used to mock various aspects of Node.js applications, including streams.

proxyquire

Proxyquire is a module used to mock dependencies during testing. It allows you to override dependencies in your modules, which can include stdin streams. This makes it a versatile tool for testing various aspects of your application.

README

node-mock-stdin

Provide a mock readable stream, useful for testing interactive CLI applications.

Maybe simple mocks for other standard files wouldn't be a terrible idea, if anyone feels like those are needed. Patches welcome.

API

• Module
  • stdin()
• MockSTDIN
  • send()
  • end()
  • restore()
  • reset()

---

Module.stdin()

example

require('mock-stdin').stdin();

Replaces the existing process.stdin value with a mock object exposing a send method (a MockSTDIN instance). This allows APIs like process.openStdin() or process.stdin.on() to operate on a mock instance.

note: Event listeners from the original process.stdin instance are not added to the mock instance. Installation of the mock should occur before any event listeners are registered.

return value: A MockSTDIN instance

---

MockSTDIN.send(data, encoding)

example

var stdin = require('mock-stdin').stdin();
stdin.send("Some text", "ascii");
stdin.send(Buffer("Some text", "Some optional encoding"));
stdin.send([
  "Array of lines",
  "  which are joined with a linefeed."
]);

// sending a null will trigger EOF and dispatch an 'end' event.
stdin.send(null);

Queue up data to be read by the stream. Results in data (and possibly end) events being dispatched.

parameters

• data: A String, Buffer, Array<String>, or null. The data parameter will result in the default encoding if specified as a string or array of strings.
• encoding: An optional encoding which is used when data is a String. Node.js's internal Readable Stream will convert the specified encoding into the output encoding, which is transcoded if necessary.

return value: The MockSTDIN instance, for chaining.

---

MockSTDIN.end()

example

var stdin = require('mock-stdin').stdin();
stdin.end();

Alias for MockSTDIN.send(null). Results in dispatching an end event.

return value: The MockSTDIN instance, for chaining.

---

MockSTDIN.restore()

example

var stdin = require('mock-stdin').stdin();
// process.stdin is now a mock stream
stdin.restore();
// process.stdin is returned to its original state

Restore the target of the mocked stream. If only a single mock stream is created, will restore the original stdin TTY stream. If multiple mock streams are created, it will restore the stream which was active at the time the mock was created.

return value: The MockSTDIN instance, for chaining.

---

MockSTDIN.reset(removeListeners)

example

var stdin = require('mock-stdin').stdin();
stdin.end();
stdin.reset();
stdin.send("some data");

Ordinarily, a Readable stream will throw when attempting to push after an EOF. This routine will reset the ended state of a Readable stream, preventing it from throwing post-EOF. This prevents being required to re-create a mock STDIN instance during certain tests where a fresh stdin is required.

If the removeListeners flag is set to true, all event listeners will also be reset. This is useful in cases where you need to emulate restarting an entire application, without fully re-creating the mock object.

parameters

• removeListeners: Boolean value which, when set to true, will remove all event listeners attached to the stream.

return value: The MockSTDIN instance, for chaining.

---

LICENSE

The MIT License (MIT)

Copyright (c) 2014 Caitlin Potter & Contributors

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.