Files
sse-session/tests/sse-session.test.ts

633 lines
25 KiB
TypeScript

import { expect, test, vi, type Mock } from 'vitest';
import { SSESession } from '../src/sse-session.js';
import { ExponentialBackoff } from '../src/utils/exponential-backoff.js';
import type { SSESessionOptions, SSEvent } from '../src/types.js';
import { SseTestStream, type SseTestStreamOptions } from './helpers/sse-stream.ts';
import { priceOracleEvents, storageEvents } from './fixtures/events.fixtures.ts';
/** URL passed to every session under test. */
const EVENTS_URL = '/events';
/** Headers required for a valid SSE response in these tests. */
const SSE_HEADERS = { 'Content-Type': 'text/event-stream' };
type FetchFn = SSESessionOptions['fetch'];
/**
* Builds a minimal ExponentialBackoff so reconnect and retry paths finish quickly in tests.
* Real production delays would make vi.waitFor-based assertions time out.
*
* @param maxAttempts - Maximum retry attempts; defaults to 1.
*/
const testRetry = (maxAttempts = 1): ExponentialBackoff => {
return new ExponentialBackoff({
baseDelay: 1,
maxDelay: 1,
maxAttempts,
growthRate: 1,
jitter: 0,
});
};
/**
* Wraps fixture chunks in a Response backed by {@link SseTestStream}.
* SseTestStream simulates a real HTTP body: chunks arrive over time and the stream
* can optionally close itself when all chunks are sent.
*
* @param chunks - Raw SSE payload strings to stream.
* @param options - Optional stream timing and close behavior.
*/
const sseFetchResponse = (chunks: string[], options: SseTestStreamOptions = {}): Response => {
return new Response(new SseTestStream(chunks, options).stream, {
status: 200,
headers: SSE_HEADERS,
});
};
/**
* Creates a vitest mock fetch that delegates to the given responder.
* SSESession requires fetch injection so tests never hit the network.
*
* @param responder - Function that returns the Response for each fetch call.
*/
const createFetchMock = (responder: (url: string, init: RequestInit) => Response | Promise<Response>): Mock<FetchFn> => {
return vi.fn(async (url: string, init: RequestInit) => responder(url, init));
};
/**
* Session defaults that disable reconnect noise unless a test opts in.
* attemptReconnect: false — transport errors should not auto-retry by default.
* persistent: false — server closing the stream should close the message iterator.
*/
const defaultSessionOptions: Partial<SSESessionOptions> = {
attemptReconnect: false,
persistent: false,
retry: testRetry(),
};
/**
* Creates an SSESession wired to the injected fetch mock.
* SSESession.create immediately calls connect(), so fetch is invoked during creation.
*
* @param fetch - Mock fetch implementation.
* @param options - Per-test session overrides merged on top of defaults.
*/
const createSession = async (fetch: FetchFn, options: Partial<SSESessionOptions> = {}): Promise<SSESession> => {
return SSESession.create(EVENTS_URL, {
...defaultSessionOptions,
onError: vi.fn(),
...options,
fetch,
});
};
/**
* Runs a callback against a session and always disconnects afterward.
* Most tests use this so session lifecycle (connect on create, disconnect on exit)
* is consistent and resources are not leaked between cases.
*
* @param fetch - Mock fetch for the session.
* @param options - Session options.
* @param run - Test body receiving the connected session.
*/
const withSession = async <T>(fetch: FetchFn, options: Partial<SSESessionOptions>, run: (session: SSESession) => Promise<T>): Promise<T> => {
const session = await createSession(fetch, options);
try {
return await run(session);
} finally {
await session.disconnect();
}
};
/**
* Reads up to `count` messages from the session's async iterator.
* Breaking out of the for-await loop early leaves the underlying stream open,
* which is intentional for tests that inspect post-read session state.
*
* @param session - Connected SSE session.
* @param count - Number of events to collect before stopping.
*/
const readMessages = async (session: SSESession, count: number): Promise<SSEvent[]> => {
const events: SSEvent[] = [];
for await (const event of session.messages) {
events.push(event);
if (events.length >= count) {
break;
}
}
return events;
};
/**
* Builds a ReadableStream that emits one chunk then errors after a delay.
* Simulates a mid-stream network failure: the client receives partial data,
* then the connection drops before the server finishes sending.
*
* @param raw - SSE payload to enqueue before the error.
* @param delayMs - Milliseconds to wait before erroring (gives the parser time to process the chunk).
*/
const failingStreamAfter = (raw: string, delayMs = 50): ReadableStream<Uint8Array> => {
const encoder = new TextEncoder();
return new ReadableStream({
async start(controller): Promise<void> {
controller.enqueue(encoder.encode(raw));
await new Promise((resolve) => setTimeout(resolve, delayMs));
controller.error(new Error('network failure'));
},
});
};
/**
* Scenario: a client opens a standard GET SSE connection.
* Verifies the session passes the correct fetch options for a spec-compliant SSE request.
*/
const testSseSessionConnectCallsFetchWithExpectedOptions = async (): Promise<void> => {
// Return one valid storage fixture event so connect succeeds and the stream stays open briefly.
const fetchMock = createFetchMock(() => sseFetchResponse([ storageEvents[0]!.raw ]));
try {
// withSession → createSession → SSESession.create → connect → fetchMock is called once.
await withSession(fetchMock, {}, async () => {
expect(fetchMock).toHaveBeenCalledWith(
EVENTS_URL,
expect.objectContaining({
method: 'GET',
cache: 'no-store',
signal: expect.any(AbortSignal),
headers: expect.objectContaining({
Accept: 'text/event-stream',
'Cache-Control': 'no-cache',
}),
}),
);
// While the stream is active the abort signal must not yet be triggered.
expect(fetchMock.mock.calls[0]?.[1]?.signal?.aborted).toBe(false);
});
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: a client connects and the application wants a lifecycle callback when the stream is ready.
* Verifies onConnected fires after the transport is established.
*/
const testSseSessionConnectInvokesOnConnected = async (): Promise<void> => {
const onConnected = vi.fn();
const fetchMock = createFetchMock(() => sseFetchResponse([ storageEvents[0]!.raw ]));
try {
await withSession(fetchMock, { onConnected }, async () => {
expect(onConnected).toHaveBeenCalledOnce();
});
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: a client is already connected and something calls connect() again (e.g. a duplicate init).
* Verifies the session does not open a second HTTP transport.
*/
const testSseSessionConnectDoesNotOpenSecondTransport = async (): Promise<void> => {
const fetchMock = createFetchMock(() => sseFetchResponse([ storageEvents[0]!.raw ]));
try {
await withSession(fetchMock, {}, async (session) => {
// Pull one event so the first transport is fully established and reading.
await readMessages(session, 1);
// Idempotent connect — should be a no-op at the fetch layer.
await session.connect();
expect(fetchMock).toHaveBeenCalledOnce();
});
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: the application attaches auth or other headers via onRequest before each fetch.
* Verifies mutations from onRequest reach the actual fetch call.
*/
const testSseSessionConnectPassesOnRequestMutations = async (): Promise<void> => {
const fetchMock = createFetchMock(() => sseFetchResponse([ storageEvents[0]!.raw ]));
try {
await withSession(
fetchMock,
{
// onRequest runs during connect and can rewrite headers/body before fetch sees them.
onRequest: async (request) => ({
...request,
headers: { ...request.headers, Authorization: 'Bearer test-token' },
}),
},
async () => {
expect(fetchMock).toHaveBeenCalledWith(
EVENTS_URL,
expect.objectContaining({
headers: expect.objectContaining({
Authorization: 'Bearer test-token',
}),
}),
);
},
);
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: some SSE endpoints require POST with a form body instead of a plain GET.
* Verifies method and body are forwarded to fetch.
*/
const testSseSessionConnectSendsPostBody = async (): Promise<void> => {
const body = new FormData();
body.set('topic', 'prices');
const fetchMock = createFetchMock(() => sseFetchResponse([ storageEvents[0]!.raw ]));
try {
await withSession(
fetchMock,
{
method: 'POST',
body,
},
async () => {
expect(fetchMock).toHaveBeenCalledWith(
EVENTS_URL,
expect.objectContaining({
method: 'POST',
body,
}),
);
},
);
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: a single long-lived connection delivers many events from different domains (LLM, oracle, storage).
* Verifies the parser and session deliver every fixture event in order through one stream.
*/
const testSseSessionDeliversMultipleFixtureEvents = async (): Promise<void> => {
const fixtures = [ ...priceOracleEvents, ...storageEvents ];
const expected = fixtures.flatMap(({ parsed }) => parsed ?? []);
// All raw payloads are concatenated into one SseTestStream response.
const fetchMock = createFetchMock(() => sseFetchResponse(fixtures.map(({ raw }) => raw)));
try {
await withSession(fetchMock, {}, async (session) => {
const received = await readMessages(session, expected.length);
expect(received).toEqual(expected);
});
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: application code listens via session.on('message') instead of the async iterator.
* Verifies the EventEmitter path receives the same parsed events as the iterator.
*/
const testSseSessionEmitsMessageEvents = async (): Promise<void> => {
const { raw, parsed } = storageEvents[0]!;
const emitted: SSEvent[] = [];
// ':\n\n' is an SSE comment/heartbeat; chunkDelayMs forces it to arrive as a separate chunk
// so incremental parsing is exercised before the real data frame.
const fetchMock = createFetchMock(() => sseFetchResponse([ ':\n\n', raw ], { chunkDelayMs: 50 }));
// Use createSession directly (not withSession) so we control disconnect timing in finally.
const session = await createSession(fetchMock, {});
try {
session.on('message', (event) => emitted.push(event));
await readMessages(session, 1);
expect(emitted).toEqual([ parsed![0] ]);
} finally {
await session.disconnect();
vi.restoreAllMocks();
}
};
/**
* Scenario: network chunks split an SSE frame at an arbitrary byte boundary.
* Verifies the internal parser buffers partial data and still emits a complete event.
*/
const testSseSessionParsesEventSplitAcrossChunks = async (): Promise<void> => {
const { raw, parsed } = storageEvents[0]!;
const mid = Math.floor(raw.length / 2);
// SseTestStream sends each array element as a separate chunk — the event is cut in half.
const fetchMock = createFetchMock(() => sseFetchResponse([ raw.slice(0, mid), raw.slice(mid) ]));
try {
await withSession(fetchMock, {}, async (session) => {
const [ event ] = await readMessages(session, 1);
expect(event).toEqual(parsed![0]);
});
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: server closes the stream after one event and the client is not in persistent mode.
* Verifies the message iterator closes and onDisconnected fires.
*/
const testSseSessionClosesOnServerCloseWhenNotPersistent = async (): Promise<void> => {
// closeWhenDone: true makes SseTestStream end the body after sending the chunk.
const fetchMock = createFetchMock(() => sseFetchResponse([ storageEvents[0]!.raw ], { closeWhenDone: true }));
const disconnected = vi.fn();
try {
// persistent defaults to false — terminal server close should shut down messages.
await withSession(fetchMock, { onDisconnected: disconnected }, async (session) => {
await readMessages(session, 1);
await vi.waitFor(() => expect(session.messages.closed).toBe(true));
expect(disconnected).toHaveBeenCalled();
});
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: server closes the stream, the message iterator closes, then the app manually reconnects.
* Verifies a second fetch opens and events flow again (non-persistent manual reconnect path).
*/
const testSseSessionReconnectsAfterTerminalClose = async (): Promise<void> => {
const fetchMock = createFetchMock(() => sseFetchResponse([ storageEvents[0]!.raw ], { closeWhenDone: true }));
// Override the default responder: first fetch closes after one event, second stays open.
fetchMock
.mockResolvedValueOnce(sseFetchResponse([ storageEvents[0]!.raw ], { closeWhenDone: true }))
.mockResolvedValueOnce(sseFetchResponse([ storageEvents[0]!.raw ]));
try {
await withSession(fetchMock, {}, async (session) => {
await readMessages(session, 1);
await vi.waitFor(() => expect(session.messages.closed).toBe(true));
// App-initiated reconnect after the first stream ended.
await session.connect();
const [ event ] = await readMessages(session, 1);
expect(event).toEqual(storageEvents[0]!.parsed![0]);
expect(fetchMock).toHaveBeenCalledTimes(2);
});
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: persistent client — server closes the stream but the session should auto-reconnect.
* Verifies two fetch calls and events from both streams arrive on the same message iterator.
*/
const testSseSessionPersistentReconnectsOnServerClose = async (): Promise<void> => {
const fetchMock = createFetchMock(() => sseFetchResponse([ priceOracleEvents[0]!.raw ], { closeWhenDone: true }));
fetchMock
.mockResolvedValueOnce(sseFetchResponse([ priceOracleEvents[0]!.raw ], { closeWhenDone: true }))
.mockResolvedValueOnce(sseFetchResponse([ priceOracleEvents[1]!.raw ]));
try {
await withSession(
fetchMock,
{
persistent: true,
retry: testRetry(2),
},
async (session) => {
const [ first, second ] = await readMessages(session, 2);
expect(first).toEqual(priceOracleEvents[0]!.parsed![0]);
expect(second).toEqual(priceOracleEvents[1]!.parsed![0]);
await vi.waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(2));
},
);
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: mid-stream network error with attemptReconnect enabled.
* Verifies the session fetches again and the iterator continues delivering events.
*/
const testSseSessionReconnectsOnTransportError = async (): Promise<void> => {
const fetchMock = createFetchMock(() => sseFetchResponse([ priceOracleEvents[0]!.raw ]));
fetchMock
// First connection: delivers one event then the stream errors (failingStreamAfter).
.mockResolvedValueOnce(new Response(failingStreamAfter(priceOracleEvents[0]!.raw), { status: 200, headers: SSE_HEADERS }))
// Second connection: clean stream with the next fixture event.
.mockResolvedValueOnce(sseFetchResponse([ priceOracleEvents[1]!.raw ]));
try {
await withSession(
fetchMock,
{
attemptReconnect: true,
retry: testRetry(2),
},
async (session) => {
const [ beforeError, recovered ] = await readMessages(session, 2);
expect(beforeError).toEqual(priceOracleEvents[0]!.parsed![0]);
expect(recovered).toEqual(priceOracleEvents[1]!.parsed![0]);
await vi.waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(2));
},
);
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: mid-stream network error with attemptReconnect disabled (default).
* Verifies the session terminates: messages close, onError runs, and an error event is emitted.
*/
const testSseSessionClosesOnTransportErrorWhenNotReconnecting = async (): Promise<void> => {
const onError = vi.fn();
const response = new Response(failingStreamAfter(priceOracleEvents[0]!.raw), { status: 200, headers: SSE_HEADERS });
const fetchMock = createFetchMock(() => response);
try {
await withSession(fetchMock, { onError }, async (session) => {
const errorEvent = new Promise<Error>((resolve) => session.once('error', resolve));
await vi.waitFor(() => expect(session.messages.closed).toBe(true));
expect(onError).toHaveBeenCalled();
await expect(errorEvent).resolves.toBeInstanceOf(Error);
});
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: the user aborts an active connection (e.g. navigation away) but may reconnect later.
* Verifies onDisconnected fires, fetch is aborted, but the message iterator stays open.
*/
const testSseSessionAbortEmitsDisconnectedAndKeepsMessagesOpen = async (): Promise<void> => {
const onDisconnected = vi.fn();
const fetchMock = createFetchMock(() => sseFetchResponse([ storageEvents[0]!.raw ]));
try {
await withSession(fetchMock, { onDisconnected }, async (session) => {
await readMessages(session, 1);
await session.abort();
expect(onDisconnected).toHaveBeenCalled();
expect(session.messages.closed).toBe(false);
});
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: the application fully tears down the session (logout, component unmount, etc.).
* Verifies disconnect closes the message iterator and emits the closed event.
*/
const testSseSessionDisconnectClosesMessagesAndEmitsClosed = async (): Promise<void> => {
const fetchMock = createFetchMock(() => sseFetchResponse([ storageEvents[0]!.raw ]));
const session = await createSession(fetchMock, {});
const closed = new Promise<void>((resolve) => session.once('closed', () => resolve()));
try {
await session.disconnect();
expect(session.messages.closed).toBe(true);
await expect(closed).resolves.toBeUndefined();
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: the server returns a non-2xx HTTP status (500).
* Verifies create rejects, onError is invoked, and the error is a real Error instance.
*/
const testSseSessionHttpErrorCallsOnErrorAndThrows = async (): Promise<void> => {
const onError = vi.fn();
const fetchMock = createFetchMock(() =>
new Response('nope', {
status: 500,
statusText: 'Internal Server Error',
}));
const expectedError = new AggregateError([ new Error('HTTP error: 500 nope') ], 'Exponential backoff max retries hit');
try {
await expect(createSession(fetchMock, { onError })).rejects.toThrow(expectedError);
expect(onError).toHaveBeenCalled();
expect(onError.mock.calls[0]?.[0]).toBeInstanceOf(Error);
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: fetch returns 200 but with a null body (misconfigured proxy or server bug).
* Verifies create rejects because SSE requires a readable stream body.
*/
const testSseSessionRejectsWhenResponseBodyIsNull = async (): Promise<void> => {
const onError = vi.fn();
const fetchMock = createFetchMock(() => new Response(null, { status: 200, headers: SSE_HEADERS }));
const expectedError = new AggregateError([ new Error('HTTP error: Response body is null') ], 'Exponential backoff max retries hit');
try {
await expect(createSession(fetchMock, { onError, retry: testRetry() })).rejects.toThrow(expectedError);
expect(onError).toHaveBeenCalled();
} finally {
vi.restoreAllMocks();
}
};
/**
* Scenario: SSE spec resume — after receiving an event with an id, reconnect should send Last-Event-ID.
* Verifies the second fetch includes the id from the first event (1234 in storageEvents[0]).
*/
const testSseSessionSendsLastEventIdOnReconnect = async (): Promise<void> => {
const { raw } = storageEvents[0]!;
let reconnectHeaders: Record<string, string> | undefined;
const fetchMock = createFetchMock(() => sseFetchResponse([ raw ]));
fetchMock
// First connection: heartbeat chunk, then the event (with id: 1234), then server closes.
.mockResolvedValueOnce(sseFetchResponse([ ':\n\n', raw ], { chunkDelayMs: 10, closeWhenDone: true }))
// Second connection: capture whatever headers the reconnect logic attached.
.mockImplementationOnce(async (_url, init) => {
reconnectHeaders = init.headers as Record<string, string>;
return sseFetchResponse([]);
});
const session = await createSession(fetchMock, { persistent: true, retry: testRetry(2) });
try {
// Registers an onRequest hook that copies the last seen event id into reconnect headers.
await SSESession.addLastEventIdReconnect(session);
await readMessages(session, 1);
await vi.waitFor(() => expect(fetchMock).toHaveBeenCalledTimes(2));
expect(reconnectHeaders?.['Last-Event-ID']).toBe('1234');
} finally {
await session.disconnect();
vi.restoreAllMocks();
}
};
const runTests = async (): Promise<void> => {
test('SSESession.connect: calls injected fetch with method, headers, and abort signal', testSseSessionConnectCallsFetchWithExpectedOptions);
test('SSESession.connect: invokes onConnected when the stream is established', testSseSessionConnectInvokesOnConnected);
test('SSESession.connect: does not open a second transport when connect is called again', testSseSessionConnectDoesNotOpenSecondTransport);
test('SSESession.connect: passes request mutations from onRequest to fetch', testSseSessionConnectPassesOnRequestMutations);
test('SSESession.connect: sends POST bodies for POST-based SSE endpoints', testSseSessionConnectSendsPostBody);
test('SSESession: delivers multiple fixture events through a single session', testSseSessionDeliversMultipleFixtureEvents);
test('SSESession: emits message events for incoming SSE frames', testSseSessionEmitsMessageEvents);
test('SSESession: parses a fixture event split across chunk boundaries', testSseSessionParsesEventSplitAcrossChunks);
test('SSESession: closes messages and emits disconnected when persistent is false', testSseSessionClosesOnServerCloseWhenNotPersistent);
test('SSESession: opens a new message stream after reconnecting following a terminal close', testSseSessionReconnectsAfterTerminalClose);
test('SSESession: reconnects when the server closes the stream and persistent is true', testSseSessionPersistentReconnectsOnServerClose);
test('SSESession: reconnects when attemptReconnect is true', testSseSessionReconnectsOnTransportError);
test('SSESession: closes messages and emits error when attemptReconnect is false', testSseSessionClosesOnTransportErrorWhenNotReconnecting);
test('SSESession.abort: aborts fetch, emits disconnected, and keeps messages open', testSseSessionAbortEmitsDisconnectedAndKeepsMessagesOpen);
test('SSESession.disconnect: closes messages and emits closed', testSseSessionDisconnectClosesMessagesAndEmitsClosed);
test('SSESession: calls onError, emits error, and throws from create on HTTP error', testSseSessionHttpErrorCallsOnErrorAndThrows);
test('SSESession: rejects when the response body is null', testSseSessionRejectsWhenResponseBodyIsNull);
test('SSESession: sends Last-Event-ID on reconnect after receiving an event with an id', testSseSessionSendsLastEventIdOnReconnect);
};
await runTests();