test: cover complete fake agent flow

packages/harness/src/index.ts

@@ -19,6 +19,7 @@ export * from "./sessions/in-memory-session-registry.js";
 export * from "./sessions/session-registry.js";
 export * from "./skills/skill-catalog.js";
 export * from "./skills/skill-event-inference.js";
+export * from "./testing/fake-agent-session.js";
 export * from "./tools/mock-ads-metrics.js";
 export * from "./tools/save-report-draft.js";
 export * from "./tools/tool-policy.js";

packages/harness/src/sessions/harness-session.ts

@@ -82,8 +82,17 @@ export class HarnessSession {
       eventStore: this.#eventStore,
       ...(skillInference === undefined ? {} : { skillInference }),
     });
+    let eventQueue = Promise.resolve();
+    let eventError: unknown;
     const unsubscribe = port.subscribe((event) => {
-      void adapter.observe(event);
+      eventQueue = eventQueue.then(async () => {
+        if (eventError !== undefined) return;
+        try {
+          await adapter.observe(event);
+        } catch (error) {
+          eventError = error;
+        }
+      });
     });
     const active: ActiveRun = {
       runId,
@@ -108,7 +117,11 @@ export class HarnessSession {
 
     void Promise.resolve()
       .then(() => port.prompt(message.text, { images }))
-      .then(() => this.#complete(active))
+      .then(async () => {
+        await eventQueue;
+        if (eventError !== undefined) throw eventError;
+        this.#complete(active);
+      })
       .catch((error: unknown) => this.#fail(active, error));
     return { runId };
   }

packages/harness/src/testing/fake-agent-session.ts

@@ -0,0 +1,46 @@
+import type { ImageContent } from "@earendil-works/pi-ai";
+import type { AgentSessionPort } from "../agent/agent-session-port.js";
+
+type Listener = (event: unknown) => void;
+type Driver = (
+  session: FakeAgentSession,
+  prompt: { text: string; images: ImageContent[] },
+) => Promise<void>;
+
+export class FakeAgentSession implements AgentSessionPort {
+  readonly #listeners = new Set<Listener>();
+  readonly prompts: Array<{ text: string; images: ImageContent[] }> = [];
+  public aborted = false;
+  public disposed = false;
+
+  public constructor(private readonly driver: Driver) {}
+
+  public subscribe(listener: Listener): () => void {
+    this.#listeners.add(listener);
+    return () => this.#listeners.delete(listener);
+  }
+
+  public async prompt(text: string, options: { images: ImageContent[] }): Promise<void> {
+    const prompt = { text, images: options.images.map((image) => ({ ...image })) };
+    this.prompts.push(prompt);
+    await this.driver(this, prompt);
+  }
+
+  public emit(event: unknown): void {
+    for (const listener of [...this.#listeners]) listener(event);
+  }
+
+  public async flush(): Promise<void> {
+    await new Promise<void>((resolve) => setTimeout(resolve, 0));
+  }
+
+  public abort(): Promise<void> {
+    this.aborted = true;
+    return Promise.resolve();
+  }
+
+  public dispose(): void {
+    this.disposed = true;
+    this.#listeners.clear();
+  }
+}