diff --git a/mock_server.js b/mock_server.js
index f848042..d83e77a 100644
--- a/mock_server.js
+++ b/mock_server.js
@@ -45,9 +45,11 @@ async function start_server () {
       .end (`foo:${res.connection.user_id}`);
   });
 
-  app.listen (3000);
-
-  return app;
+  return new Promise ((res) => {
+    const listener = app.listen (0, () => {
+      res (listener.address ().port);
+    });
+  });
 }
 
 module.exports = { start_server };
diff --git a/package.json b/package.json
index 7f9d0b5..9f45e13 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,7 @@
     "@sapphirecode/eslint-config": "^2.1.4",
     "@stryker-mutator/core": "^3.2.3",
     "@stryker-mutator/javascript-mutator": "^3.2.3",
-    "ava": "^3.8.2",
+    "ava": "^3.10.1",
     "eslint": "^7.0.0",
     "express": "^4.17.1",
     "node-fetch": "^2.6.0",
@@ -28,11 +28,11 @@
   },
   "dependencies": {
     "@sapphirecode/consts": "^1.1.18",
-    "@sapphirecode/password-helper": "^1.0.35",
-    "@sapphirecode/crypto-helper": "^1.1.44"
+    "@sapphirecode/crypto-helper": "^1.1.44",
+    "@sapphirecode/password-helper": "^1.0.35"
   },
   "files": [
     "LICENSE",
     "index.js"
   ]
-}
\ No newline at end of file
+}
diff --git a/test/index.js b/test/index.js
index 5e1dd75..ae8df09 100644
--- a/test/index.js
+++ b/test/index.js
@@ -14,27 +14,35 @@ const client = require ('@sapphirecode/auth-client-helper');
 const consts = require ('@sapphirecode/consts');
 const fetch = require ('node-fetch');
 
+let port = 0;
+
 test.before (async () => {
-  await mock_server.start_server ();
+  port = await mock_server.start_server ();
 });
 
-test ('login', async (t) => {
+test.only ('login', async (t) => {
+  console.log ('logging in');
+  console.log ('port:', port);
   const session = await client.login (
     'testuser',
     'foo',
-    'http://localhost:3000'
+    `http://localhost:${port}`
   );
-
+  console.log ('server respond');
   t.is (typeof session, 'string');
 
-  const resp = await fetch ('http://localhost:3000', { headers: { session } });
+  const resp = await fetch (
+    `http://localhost:${port}`,
+    { headers: { session } }
+  );
 
   t.is (resp.status, consts.http.status_ok);
   t.is (await resp.text (), 'foo:69');
+  console.log ('done test');
 });
 
 test ('allow access to excluded paths', async (t) => {
-  const resp = await fetch ('http://localhost:3000/noauthreg');
+  const resp = await fetch (`http://localhost:${port}/noauthreg`);
 
   t.is (resp.status, consts.http.status_ok);
   t.is (await resp.text (), 'foo:undefined');
@@ -42,7 +50,7 @@ test ('allow access to excluded paths', async (t) => {
 
 test ('allow access to excluded paths with correct method', async (t) => {
   const resp = await fetch (
-    'http://localhost:3000/noauthobj',
+    `http://localhost:${port}/noauthobj`,
     { method: 'POST' }
   );
 
@@ -52,7 +60,7 @@ test ('allow access to excluded paths with correct method', async (t) => {
 
 test ('reject access to excluded paths with wrong method', async (t) => {
   const resp = await fetch (
-    'http://localhost:3000/noauthobj'
+    `http://localhost:${port}/noauthobj`
   );
 
   t.is (resp.status, consts.http.status_unauthorized);
@@ -62,7 +70,7 @@ test ('reject invalid user', async (t) => {
   await t.throwsAsync (client.login (
     'foo',
     'foo',
-    'http://localhost:3000'
+    `http://localhost:${port}`
   ));
 });
 
@@ -70,6 +78,6 @@ test ('reject invalid password', async (t) => {
   await t.throwsAsync (client.login (
     'testuser',
     'bar',
-    'http://localhost:3000'
+    `http://localhost:${port}`
   ));
 });
diff --git a/yarn.lock b/yarn.lock
index eff5e8f..d8bd5a1 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -592,7 +592,7 @@ astral-regex@^2.0.0:
   resolved "https://registry.yarnpkg.com/astral-regex/-/astral-regex-2.0.0.tgz#483143c567aeed4785759c0865786dc77d7d2e31"
   integrity sha512-Z7tMw1ytTXt5jqMcOP+OQteU1VuNK9Y02uuJtKQ1Sv69jXQKKg5cibLwGJow8yzZP+eAc18EmLGPal0bp36rvQ==
 
-ava@^3.8.2:
+ava@^3.10.1:
   version "3.10.1"
   resolved "https://registry.yarnpkg.com/ava/-/ava-3.10.1.tgz#a4e68b1a2bb248fa0d96529d23dd83f57082e944"
   integrity sha512-+w86ZHyFHIGCABi7NUrn/WJMyC+fDj0BSIlFNVS45WDKAD5vxbIiDWeclctxOOc2KDPfQD7tFOURSBz0FBLD0A==