I'm looking for a way to test and verify the different behaviors of stdin.isTTY in my Node CLI tool implementation.
In my Node CLI tool, data can be passed either through the terminal or as command line arguments:
cli.js
#!/usr/bin/env node
const { stdin, exit } = require('process');
const parseCliArgs = (argv) => {
// parse args...
return argv;
};
const readFromStdin = async () => {
stdin.setEncoding('utf-8');
return new Promise(((resolve, reject) => {
let data = '';
stdin.on('readable', () => {
let chunk;
while ((chunk = stdin.read()) !== null) {
data += chunk;
}
});
stdin.on('end', () => {
resolve(data);
});
stdin.on('error', err => reject(err));
}));
};
const main = async (argv) => {
let args;
console.info('isTTY: ', stdin.isTTY);
if (stdin.isTTY) {
console.info('Parse arguments');
args = parseCliArgs(argv);
} else {
console.info('Read from stdin');
args = await readFromStdin();
}
console.info(args);
};
main(process.argv)
.catch((err) => {
console.error(err);
exit(1);
});
The tool functions correctly when used from the terminal by piping data to the CLI script:
$ echo "hello" | ./cli.js
isTTY: undefined
Read from stdin
hello
Data is also successfully passed as command line arguments:
$ ./cli.js hello
isTTY: true
Parse arguments
[
'/usr/local/Cellar/node/13.2.0/bin/node',
'[my local path]/cli.js',
'hello'
]
I've written tests to ensure these behaviors are verified:
cli.spec.js
const { execSync } = require('child_process');
// pipe stdio and stdout from child process to node's stdio and stdout
const CHILD_PROCESS_OPTIONS = { stdio: 'inherit' };
describe('cli test', () => {
it('pipe data to CLI tool', () => {
const command = `echo "hello" | ${__dirname}/cli.js`;
execSync(command, CHILD_PROCESS_OPTIONS);
});
it('pass data as CLI args', () => {
const command = `${__dirname}/cli.js "hello"`;
execSync(command, CHILD_PROCESS_OPTIONS);
});
});
The pipe data to CLI tool test runs as expected, but the pass data as CLI args test hangs indefinitely. The output shows:
isTTY: undefined
Read from stdin
This leads me to believe that stdin.isTTY is not being handled correctly, causing the test to hang because the promise from readFromStdin() remains unresolved.
- How can I resolve the issue with the
pass data as CLI argstest? - Is there a way to mock
process.stdin.isTTYin the child process?