feat(port): choose an ephemeral port in test mode

Author: djMax

src/config/index.ts

@@ -1,4 +1,5 @@
 import fs from 'fs';
+import net from 'net';
 import path from 'path';
 
 import {
@@ -10,6 +11,7 @@ import {
 } from '@sesamecare-oss/confit';
 
 import { findPort } from '../development/port-finder';
+import { isTest } from '../env';
 
 import type { ConfigurationSchema } from './schema';
 
@@ -55,6 +57,28 @@ async function addDefaultConfiguration<Config extends ConfigurationSchema = Conf
   }
 }
 
+async function getEphemeralPort(): Promise<number> {
+  return new Promise((resolve, reject) => {
+    const server = net.createServer();
+
+    server.listen(0, () => {
+      const address = server.address();
+      if (typeof address === 'string' || !address) {
+        reject(new Error('Invalid address'));
+        return;
+      }
+      const port = address.port; // Retrieve the ephemeral port
+      server.close((err) => {
+        if (err) {
+          reject(err);
+        } else {
+          resolve(port);
+        }
+      });
+    });
+  });
+}
+
 export interface ServiceConfigurationSpec {
   // The LAST configuration is the most "specific" - if a configuration value
   // exists in all directories, the last one wins
@@ -93,7 +117,8 @@ export async function loadConfiguration<Config extends ConfigurationSchema>({
   // configured to auto-select
   const serverConfig = loaded.get().server;
   if (serverConfig.port === 0) {
-    const port = (await findPort(8001)) as number;
+    const portPromise: Promise<number> = isTest() ? getEphemeralPort() : findPort(8001);
+    const port = await portPromise;
     const store = loaded.get();
     store.server = store.server || {};
     store.server.port = port;

src/development/port-finder.ts

@@ -36,5 +36,5 @@ export async function findPort(start: number) {
       return p;
     }
   }
-  return null;
+  return 0;
 }