src/vs/workbench/services/extensions/common/extensionHostManager.ts/ExtensionHostManager/extensionTestsSendExit
class ExtensionHostManager:	public async extensionTestsSendExit(exitCode: number): Promise<void> {
		const proxy = await this._getProxy();
		if (!proxy) {
			return;
		}
		// This method does not wait for the actual RPC to be confirmed
		// It waits for the socket to drain (i.e. the message has been sent)
		// It also times out after 5s in case drain takes too long
		proxy.$extensionTestsExit(exitCode);
		if (this._rpcProtocol) {
			await Promise.race([this._rpcProtocol.drain(), timeout(5000)]);
		}
	}