diff --git a/deno.lock b/deno.lock
new file mode 100644
index 0000000..7b2008d
--- /dev/null
+++ b/deno.lock
@@ -0,0 +1,33 @@
+{
+  "version": "5",
+  "specifiers": {
+    "jsr:@std/assert@*": "1.0.19",
+    "jsr:@std/internal@^1.0.12": "1.0.14"
+  },
+  "jsr": {
+    "@std/assert@1.0.19": {
+      "integrity": "eaada96ee120cb980bc47e040f82814d786fe8162ecc53c91d8df60b8755991e",
+      "dependencies": [
+        "jsr:@std/internal"
+      ]
+    },
+    "@std/internal@1.0.14": {
+      "integrity": "291516b3d4c35024d6ffbc0a9df5bf4c64116e05b50012cf846710152d2ffdf7"
+    }
+  },
+  "workspace": {
+    "packageJson": {
+      "dependencies": [
+        "npm:@biomejs/biome@2.5.12",
+        "npm:@types/bun@1.4.0",
+        "npm:jsdom@^30.0.1",
+        "npm:lz-string@1.5.0",
+        "npm:solid-js@1.9.15",
+        "npm:typescript@7.0.2",
+        "npm:vite-plugin-solid@2.11.14",
+        "npm:vite@8.2.2",
+        "npm:vitest@5"
+      ]
+    }
+  }
+}
diff --git a/server/client.test.ts b/server/client.test.ts
new file mode 100644
index 0000000..1a972c6
--- /dev/null
+++ b/server/client.test.ts
@@ -0,0 +1,59 @@
+/// <reference lib="deno.ns" />
+import { assertEquals } from "jsr:@std/assert";
+
+const url = "ws://0.0.0.0:6969";
+
+function connect(): Promise<WebSocket> {
+	return new Promise((resolve, reject) => {
+		const socket = new WebSocket(url);
+		socket.onopen = () => resolve(socket);
+		socket.onerror = (e) => reject(e);
+	});
+}
+
+function nextMessage(socket: WebSocket): Promise<unknown> {
+	return new Promise((resolve, reject) => {
+		const onMessage = (e: MessageEvent) => {
+			socket.removeEventListener("message", onMessage);
+			try {
+				resolve(JSON.parse(e.data));
+			} catch {
+				resolve(e.data);
+			}
+		};
+		socket.addEventListener("message", onMessage);
+		socket.addEventListener("error", reject, { once: true });
+	});
+}
+
+function closeAndWait(socket: WebSocket): Promise<void> {
+	return new Promise((resolve) => {
+		if (socket.readyState === WebSocket.CLOSED) return resolve();
+		socket.onclose = () => resolve();
+		socket.close();
+	});
+}
+
+Deno.test("broadcasts a message from one client to another", async () => {
+	const a = await connect(); // 1
+	const b = await connect(); // 2
+
+	const received = await nextMessage(b);
+	assertEquals(received, "2 has joined!");
+
+	await closeAndWait(a);
+	await closeAndWait(b);
+});
+
+Deno.test("removes a client from broadcast after it disconnects", async () => {
+	// test are executed in a row so the ID will just increment
+	const a = await connect(); // 3
+	const b = await connect(); // 4
+
+	await closeAndWait(b);
+
+	const msg = await nextMessage(a);
+	assertEquals(msg, "4 has left!");
+
+	await closeAndWait(a);
+});