pygienium/tests/agent-runner.test.ts

/**
 * agent-runner.test.ts — unit tests for the session event accumulator.
 *
 * `applySessionEvent` runs synchronously inside the SDK's event pipeline; a
 * throw there crashes the host (the SDK's run-failure path re-emits events
 * through the same callback → stack overflow), stranding run-state at the
 * phase boundary. These tests pin the handler to never throw on the partial /
 * malformed event shapes streaming sessions actually emit.
 */
import { describe, expect, it } from "bun:test";
import {
	applySessionEvent,
	type SessionEventAccumulator,
} from "../src/agent-runner.js";
import type { AgentSessionEvent } from "@earendil-works/pi-coding-agent";

function fresh(): SessionEventAccumulator {
	return { text: "" };
}

/** Build a typed-as-unknown event so malformed shapes compile in tests. */
function event(shape: unknown): AgentSessionEvent {
	return shape as AgentSessionEvent;
}

describe("applySessionEvent", () => {
	it("accumulates text_delta stream events in order", () => {
		const acc = fresh();
		applySessionEvent(
			acc,
			event({
				type: "message_update",
				assistantMessageEvent: { type: "text_delta", delta: "foo" },
			}),
		);
		applySessionEvent(
			acc,
			event({
				type: "message_update",
				assistantMessageEvent: { type: "text_delta", delta: "bar" },
			}),
		);
		expect(acc.text).toBe("foobar");
	});

	it("does not throw on a message_update with no assistantMessageEvent", () => {
		const acc = fresh();
		expect(() =>
			applySessionEvent(acc, event({ type: "message_update" })),
		).not.toThrow();
		expect(acc.text).toBe("");
	});

	it("does not throw on a message_update with an unknown event shape", () => {
		const acc = fresh();
		expect(() => applySessionEvent(acc, event({ type: "bogus_event" }))).not.toThrow();
		expect(() => applySessionEvent(acc, event(null))).not.toThrow();
		expect(() => applySessionEvent(acc, event(undefined))).not.toThrow();
		expect(acc.text).toBe("");
	});

	it("captures full text + stopReason from message_end when nothing streamed", () => {
		const acc = fresh();
		applySessionEvent(
			acc,
			event({
				type: "message_end",
				message: {
					role: "assistant",
					stopReason: "stop",
					content: [{ type: "text", text: "full report" }],
				},
			}),
		);
		expect(acc.text).toBe("full report");
		expect(acc.stopReason).toBe("stop");
	});

	it("does not throw on a message_end with no message", () => {
		const acc = fresh();
		expect(() => applySessionEvent(acc, event({ type: "message_end" }))).not.toThrow();
		expect(acc.text).toBe("");
	});

	it("records an errorMessage surfaced on the final message", () => {
		const acc = fresh();
		applySessionEvent(
			acc,
			event({
				type: "message_end",
				message: { role: "assistant", errorMessage: "upstream 529" },
			}),
		);
		expect(acc.errorMessage).toBe("upstream 529");
	});

	it("forwards stream-driving events and swallows a throwing forwarder", () => {
		const originalError = console.error;
		console.error = () => {};
		try {
			const forwarded: string[] = [];
			const forward = (ev: AgentSessionEvent) => {
				forwarded.push(ev.type);
				if (ev.type === "tool_execution_end") throw new Error("renderer boom");
			};
			const acc = fresh();
			applySessionEvent(
				acc,
				event({ type: "tool_execution_start", toolName: "bash" }),
				forward,
			);
			applySessionEvent(
				acc,
				event({ type: "tool_execution_end", toolName: "bash" }),
				forward,
			);
			expect(forwarded).toEqual(["tool_execution_start", "tool_execution_end"]);
		} finally {
			console.error = originalError;
		}
	});

	it("does not forward non-stream-driving events", () => {
		const forwarded: string[] = [];
		const acc = fresh();
		applySessionEvent(
			acc,
			event({ type: "message_update", assistantMessageEvent: { type: "text_delta", delta: "x" } }),
			(ev) => forwarded.push(ev.type),
		);
		applySessionEvent(acc, event({ type: "agent_settled" }), (ev) =>
			forwarded.push(ev.type),
		);
		expect(forwarded).toEqual([]);
		expect(acc.text).toBe("x");
	});
});