diff --git a/tests/stress/experiment/client/src/App.jsx b/tests/stress/experiment/client/src/App.jsx
index 7a8fae4..c445cc5 100644
--- a/tests/stress/experiment/client/src/App.jsx
+++ b/tests/stress/experiment/client/src/App.jsx
@@ -1,5 +1,8 @@
 import { EmpiricaClassic } from "@empirica/core/player/classic";
-import { EmpiricaContext } from "@empirica/core/player/classic/react";
+import {
+  EmpiricaContext,
+  usePlayer,
+} from "@empirica/core/player/classic/react";
 import { EmpiricaMenu, EmpiricaParticipant } from "@empirica/core/player/react";
 import React from "react";
 import { Game } from "./Game";
@@ -11,6 +14,9 @@ export default function App() {
   const { protocol, host } = window.location;
   const url = `${protocol}//${host}/query`;
 
+  // const introSteps = function () {
+  //   return [DemoIntro];
+  // };
   // const introSteps = [DemoIntro];
   const introSteps = [];
 
@@ -35,11 +41,17 @@ export default function App() {
 }
 
 export function DemoIntro({ next }) {
+  const player = usePlayer();
+
+  if (player.get("treatment")) {
+    console.log("player treatment found");
+  }
+
   return (
     <div>
       <h2 data-test="intro-step">Intro</h2>
 
-      <button onClick={next}>
+      <button data-test="submit-intro-step" onClick={next}>
         <p>Next</p>
       </button>
     </div>
diff --git a/tests/stress/tests/actor.js b/tests/stress/tests/actor.js
index f736f7e..7705fe5 100644
--- a/tests/stress/tests/actor.js
+++ b/tests/stress/tests/actor.js
@@ -1,5 +1,6 @@
 import chalk from "chalk";
 import { error } from "./helpers";
+import { sleep } from "./utils";
 
 export class Actor {
   constructor(ctx, name, url) {
@@ -14,6 +15,7 @@ export class Actor {
     this.wsSent = [];
     this.wsReceived = [];
     this.wsClose = [];
+    this.matchingRegexes = [];
   }
 
   async start(context) {
@@ -25,6 +27,13 @@ export class Actor {
         return;
       }
 
+      for (const { regex, cb } of this.matchingRegexes) {
+        if (regex.test(text)) {
+          cb();
+          return;
+        }
+      }
+
       console.info(this.msgTypeConsole(msg.type()), text);
     });
 
@@ -58,6 +67,34 @@ export class Actor {
     );
   }
 
+  async expectLogMatching(regex, cb, options = { wait: 5000, interval: 200 }) {
+    const start = Date.now();
+
+    let matched = false;
+    this.matchingRegexes.push({
+      regex,
+      cb: (text) => {
+        matched = true;
+      },
+    });
+
+    await cb();
+
+    while (true) {
+      if (matched) {
+        return;
+      }
+
+      if (Date.now() - start > options.wait) {
+        break;
+      }
+
+      await sleep(options.interval);
+    }
+
+    throw new Error(`log not found ${regex} within ${options.wait}ms`);
+  }
+
   /**
    * Listen to WSs.
    * @param {Object} cbs - Callbacks.
diff --git a/tests/stress/tests/intro.spec.js b/tests/stress/tests/intro.spec.js
new file mode 100644
index 0000000..70a9b67
--- /dev/null
+++ b/tests/stress/tests/intro.spec.js
@@ -0,0 +1,58 @@
+// @ts-check
+/// <reference path="./index.d.ts" />
+
+const { test } = require("@playwright/test");
+import { Context } from "./context";
+import { adminNewBatch, quickGame } from "./admin";
+import {
+  gameStart,
+  playerSignIn,
+  playerStart,
+  submitIntroStep,
+  submitStage,
+  waitGameFinished,
+} from "./player";
+import { sleep } from "./utils";
+
+// At the moment, we use the same empirica server for all tests, so we need to
+// run them serially. This will change when we have a dedicated server for each
+// test.
+test.describe.configure({ mode: "serial" });
+
+// This test is a test to see if the player.get("treatment") is working
+// correctly in the intro step.
+// WARNING: this must be run with:
+//   const introSteps = [DemoIntro];
+// in the App.jsx file. This cannot be run with other tests and is normally
+// disabled. When you need to run it, mark this test with .only and run it
+// separately.
+test.skip("intro player treament", async ({ browser }) => {
+  const ctx = new Context(browser);
+
+  const playerCount = 1;
+  const roundCount = 1;
+  const stageCount = 1;
+
+  ctx.logMatching(/player treatment found/);
+
+  await ctx.start();
+  await ctx.addPlayers(playerCount);
+  ctx.players[0].logWS();
+  ctx.players[0].listenScope("game");
+
+  await ctx.applyAdmin(
+    adminNewBatch({
+      treatmentConfig: quickGame(playerCount, roundCount, stageCount),
+    })
+  );
+
+  await ctx.players[0].expectLogMatching(/player treatment found/, async () => {
+    await ctx.applyPlayers(playerSignIn);
+    await ctx.applyPlayers(submitIntroStep);
+  });
+  await ctx.applyPlayers(gameStart);
+  await ctx.applyPlayers(submitStage);
+  await ctx.applyPlayers(waitGameFinished);
+
+  await ctx.close();
+});
diff --git a/tests/stress/tests/player.js b/tests/stress/tests/player.js
index c127985..16fd2e0 100644
--- a/tests/stress/tests/player.js
+++ b/tests/stress/tests/player.js
@@ -338,6 +338,22 @@ export class Player extends Actor {
   }
 }
 
+export const playerSignIn = new Step("start game", async (actor) => {
+  // Fill the form
+  actor.info("fill form");
+  await actor.page.locator("input#playerID").fill(actor.uniqueID);
+  await actor.page.locator(`button[type="submit"]`).click();
+});
+
+export const gameStart = new Step("start game", async (actor) => {
+  // Wait for first stage to be visible
+  actor.info("signed in");
+  await actor.page.getByTestId("stage-ongoing").waitFor({ timeout: 3000000 });
+
+  actor.info("game started");
+  await actor.screenshot("game started");
+});
+
 export const playerStart = new Step("start game", async (actor) => {
   // Fill the form
   actor.info("fill form");
@@ -364,6 +380,11 @@ export const submitStage = new Step("submit stage", async (actor) => {
   // await actor.page.getByTestId("submitted").waitFor({ timeout: 5000 });
 });
 
+export const submitIntroStep = new Step("submit intro step", async (actor) => {
+  await actor.page.getByTestId("intro-step").waitFor({ timeout: 5000 });
+  await actor.page.getByTestId("submit-intro-step").click({ timeout: 5000 });
+});
+
 export const waitNextStage = new Step("wait next stage", async (actor) => {
   // Make sure the previous stage is finished
   await actor.page