/*
Copyright 2025 Google LLC
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
https://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
/**
* Waits for a specific string to appear in a stream's output.
* This is useful for synchronizing tests with asynchronous child processes,
* ensuring that a server or process has started and emitted an
* expected "ready" message before proceeding with test assertions.
*
* @param {ReadableStream} stream - The stream to listen to (e.g., process.stdout or process.stderr).
* @param {string} str - The string to wait for in the stream's output.
* @param {number} [timeoutMs=7000] - The maximum time in milliseconds to wait before rejecting.
* @returns {Promise<string>} A promise that resolves with the accumulated data
* when the string is found, or rejects if the timeout is reached.
*/
export async function waitForString(stream, str, timeoutMs = 7000) {
let accumulatedData = '';
return new Promise((resolve, reject) => {
const timeout = setTimeout(() => {
stream.removeListener('data', onData);
reject(
new Error(`waitForString timed out after ${timeoutMs}ms waiting for "${str}".
Saw:
${accumulatedData}`)
);
}, timeoutMs);
function onData(data) {
accumulatedData += data.toString();
if (accumulatedData.includes(str)) {
clearTimeout(timeout);
stream.removeListener('data', onData);
resolve(accumulatedData);
}
}
stream.on('data', onData);
});
}
