What is cli-mock-stdin used for?

To simulate user input in tests by replacing process.stdin with a mock stream.

Can I test multi-step prompts?

Yes—pass an inputs array with each user response in order to drive the prompts.

How is process.stdin restored after tests?

runWithStdin uses a finally block to reset process.stdin to the original stream.

cli-mock-stdin

Scanned

npx machina-cli add skill a5c-ai/babysitter/cli-mock-stdin --openclaw

Files (1)

SKILL.md

996 B

CLI Mock Stdin

Create mock stdin utilities for testing.

Generated Patterns

import { Readable } from 'stream';

export function mockStdin(inputs: string[]): Readable {
  let index = 0;
  return new Readable({
    read() {
      if (index < inputs.length) {
        setTimeout(() => {
          this.push(inputs[index++] + '\n');
        }, 10);
      } else {
        this.push(null);
      }
    },
  });
}

export async function runWithStdin(
  cmd: () => Promise<void>,
  inputs: string[]
): Promise<void> {
  const originalStdin = process.stdin;
  Object.defineProperty(process, 'stdin', { value: mockStdin(inputs) });
  try {
    await cmd();
  } finally {
    Object.defineProperty(process, 'stdin', { value: originalStdin });
  }
}

Target Processes

cli-unit-integration-testing
interactive-prompt-system

Source

git clone https://github.com/a5c-ai/babysitter/blob/main/plugins/babysitter/skills/babysit/process/specializations/cli-mcp-development/skills/cli-mock-stdin/SKILL.md

View on GitHub

Overview

cli-mock-stdin provides utilities to simulate user input in Node.js CLI tests. It includes mockStdin to create a stream of predefined lines and runWithStdin to swap process.stdin during test execution. This makes interactive prompts deterministic and testable in unit and integration tests.

How This Skill Works

mockStdin(inputs) returns a Readable stream that pushes each input line with a newline. runWithStdin(cmd, inputs) temporarily replaces process.stdin with the mock stream, executes cmd, and restores the original stdin in a finally block.

When to Use It

Unit tests for CLI commands that read from stdin
Integration tests for interactive prompts and workflows
Automated end-to-end tests involving user input sequences
Testing prompts with multiple or optional questions
Verifying behavior with delayed or repeated inputs

Quick Start

Step 1: Import mockStdin and runWithStdin from the module
Step 2: Prepare an inputs array representing user responses
Step 3: Call runWithStdin(() => yourTestCommand(), inputs) and await it

Best Practices

Keep inputs realistic and cover edge cases (empty lines, invalid input)
Ensure process.stdin is restored in a finally block after cmd completes
Use small, deterministic delays to mimic user pacing
Combine with mocks for external dependencies to stabilize tests
Test multiple prompt paths by varying the inputs array

Example Use Cases

Test a login CLI that asks for username and password in sequence
Validate a survey CLI that records multiple user answers
Verify a confirmation prompt (y/n) flow before performing an action
Test a CLI that reads data from stdin and processes lines
Check error handling when users provide unexpected inputs

Frequently Asked Questions

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