fix: improve SSE conformance test validation (SEP-1699)

Enhance timing validation and event ordering checks:

Client test (sse-retry):
- Add "very late" threshold (>2x retry value) as FAILURE
- Distinguish between slightly late (WARNING) and very late (FAILURE)

Server test (sse-polling):
- Check that priming event is sent immediately (first event)
- Warn if server disconnects without sending event ID first

Author: felixweinberger

src/scenarios/client/sse-retry.ts

@@ -26,6 +26,7 @@ export class SSERetryScenario implements Scenario {
   // Tolerances for timing validation
   private readonly EARLY_TOLERANCE = 50; // Allow 50ms early for scheduler variance
   private readonly LATE_TOLERANCE = 200; // Allow 200ms late for network/event loop
+  private readonly VERY_LATE_MULTIPLIER = 2; // If >2x retry value, client is likely ignoring it
 
   async start(): Promise<ScenarioUrls> {
     return new Promise((resolve, reject) => {
@@ -237,8 +238,10 @@ export class SSERetryScenario implements Scenario {
     const maxExpected = this.retryValue + this.LATE_TOLERANCE;
 
     const tooEarly = actualDelay < minExpected;
-    const tooLate = actualDelay > maxExpected;
-    const withinTolerance = !tooEarly && !tooLate;
+    const slightlyLate = actualDelay > maxExpected;
+    const veryLate =
+      actualDelay > this.retryValue * this.VERY_LATE_MULTIPLIER;
+    const withinTolerance = !tooEarly && !slightlyLate;
 
     let status: 'SUCCESS' | 'FAILURE' | 'WARNING' = 'SUCCESS';
     let errorMessage: string | undefined;
@@ -247,10 +250,14 @@ export class SSERetryScenario implements Scenario {
       // Client reconnected too soon - MUST violation
       status = 'FAILURE';
       errorMessage = `Client reconnected too early (${actualDelay.toFixed(0)}ms instead of ${this.retryValue}ms). Client MUST respect the retry field and wait the specified time.`;
-    } else if (tooLate) {
-      // Client reconnected too late - not a spec violation but suspicious
+    } else if (veryLate) {
+      // Client reconnected way too late - likely ignoring retry field entirely
+      status = 'FAILURE';
+      errorMessage = `Client reconnected very late (${actualDelay.toFixed(0)}ms instead of ${this.retryValue}ms). Client appears to be ignoring the retry field and using its own backoff strategy.`;
+    } else if (slightlyLate) {
+      // Client reconnected slightly late - not a spec violation but suspicious
       status = 'WARNING';
-      errorMessage = `Client reconnected late (${actualDelay.toFixed(0)}ms instead of ${this.retryValue}ms). This is acceptable but may indicate the client is ignoring the retry field and using its own backoff.`;
+      errorMessage = `Client reconnected slightly late (${actualDelay.toFixed(0)}ms instead of ${this.retryValue}ms). This is acceptable but may indicate network delays.`;
     }
 
     this.checks.push({
@@ -272,11 +279,13 @@ export class SSERetryScenario implements Scenario {
         actualDelayMs: Math.round(actualDelay),
         minAcceptableMs: minExpected,
         maxAcceptableMs: maxExpected,
+        veryLateThresholdMs: this.retryValue * this.VERY_LATE_MULTIPLIER,
         earlyToleranceMs: this.EARLY_TOLERANCE,
         lateToleranceMs: this.LATE_TOLERANCE,
         withinTolerance,
         tooEarly,
-        tooLate,
+        slightlyLate,
+        veryLate,
         connectionCount: this.connectionTimestamps.length
       }
     });

src/scenarios/server/sse-polling.ts

@@ -71,6 +71,7 @@ export class ServerSSEPollingScenario implements ClientScenario {
       // Parse SSE stream
       let hasEventId = false;
       let hasPrimingEvent = false;
+      let primingEventIsFirst = false;
       let hasRetryField = false;
       let retryValue: number | undefined;
       let firstEventId: string | undefined;
@@ -130,6 +131,10 @@ export class ServerSSEPollingScenario implements ClientScenario {
               event.data.trim() === ''
             ) {
               hasPrimingEvent = true;
+              // Check if priming event is the first event (SEP-1699 says "immediately")
+              if (eventCount === 1) {
+                primingEventIsFirst = true;
+              }
             }
           }
 
@@ -143,13 +148,26 @@ export class ServerSSEPollingScenario implements ClientScenario {
         clearTimeout(timeout);
       }
 
-      // Check 1: Server SHOULD send priming event with ID
+      // Check 1: Server SHOULD send priming event with ID immediately
+      let primingStatus: 'SUCCESS' | 'WARNING' = 'SUCCESS';
+      let primingErrorMessage: string | undefined;
+
+      if (!hasPrimingEvent) {
+        primingStatus = 'WARNING';
+        primingErrorMessage =
+          'Server did not send priming event with id and empty data. This is a SHOULD requirement for SEP-1699.';
+      } else if (!primingEventIsFirst) {
+        primingStatus = 'WARNING';
+        primingErrorMessage =
+          'Priming event was not sent immediately (not the first event). SEP-1699 says server SHOULD immediately send the priming event.';
+      }
+
       checks.push({
         id: 'server-sse-priming-event',
         name: 'ServerSendsPrimingEvent',
         description:
-          'Server SHOULD send SSE event with id and empty data to prime client for reconnection',
-        status: hasPrimingEvent ? 'SUCCESS' : 'WARNING',
+          'Server SHOULD immediately send SSE event with id and empty data to prime client for reconnection',
+        status: primingStatus,
         timestamp: new Date().toISOString(),
         specReferences: [
           {
@@ -159,13 +177,12 @@ export class ServerSSEPollingScenario implements ClientScenario {
         ],
         details: {
           hasPrimingEvent,
+          primingEventIsFirst,
           hasEventId,
           firstEventId,
           eventCount
         },
-        errorMessage: !hasPrimingEvent
-          ? 'Server did not send priming event with id and empty data. This is a SHOULD requirement for SEP-1699.'
-          : undefined
+        errorMessage: primingErrorMessage
       });
 
       // Check 2: Server SHOULD send retry field before disconnect
@@ -191,13 +208,23 @@ export class ServerSSEPollingScenario implements ClientScenario {
           : undefined
       });
 
-      // Check 3: Server MAY close connection (informational)
+      // Check 3: Server MAY close connection after sending event ID
+      // Per SEP-1699, server can only close "if it has sent an SSE event with an event ID"
+      let disconnectStatus: 'SUCCESS' | 'WARNING' | 'INFO' = 'INFO';
+      let disconnectMessage: string | undefined;
+
+      if (disconnected && !hasEventId) {
+        disconnectStatus = 'WARNING';
+        disconnectMessage =
+          'Server closed connection without sending an event ID first. SEP-1699 allows disconnect only after sending event ID.';
+      }
+
       checks.push({
         id: 'server-sse-disconnect',
         name: 'ServerDisconnectBehavior',
         description:
           'Server MAY close connection after sending event ID (informational)',
-        status: 'INFO',
+        status: disconnectStatus,
         timestamp: new Date().toISOString(),
         specReferences: [
           {
@@ -207,10 +234,12 @@ export class ServerSSEPollingScenario implements ClientScenario {
         ],
         details: {
           disconnected,
+          hasEventId,
           eventCount,
           hasRetryField,
           retryValue
-        }
+        },
+        errorMessage: disconnectMessage
       });
     } catch (error) {
       checks.push({