chore(test): Add integration test scaffolding for real-world ICS data

tests/integration_test.ts

@@ -0,0 +1,70 @@
+import { assertEquals, assert } from "jsr:@std/assert";
+import { convertIcsCalendar } from "https://esm.sh/ts-ics@2.4.0";
+import { expandRecurrences, resolveEventStart, localDateString } from "../icalendar.ts";
+
+Deno.test("Integration - parse and expand real-world ICS samples", async () => {
+  const testDataDir = "./test_data";
+  let files: string[] = [];
+  try {
+    for await (const dirEntry of Deno.readDir(testDataDir)) {
+      if (dirEntry.isFile && dirEntry.name.endsWith(".ics")) {
+        files.push(`${testDataDir}/${dirEntry.name}`);
+      }
+    }
+  } catch {
+    console.warn("⚠️ No test_data directory found or accessible. Skipping real-data integration test.");
+    // We might be running from root
+  }
+
+  if (files.length === 0) {
+    // Try current dir if test_data is empty (fallback for CI or root execution)
+    try {
+        for await (const dirEntry of Deno.readDir(".")) {
+            if (dirEntry.isFile && dirEntry.name.endsWith(".ics") && dirEntry.name !== "PLUG.md") {
+                files.push(dirEntry.name);
+            }
+        }
+    } catch {
+        // ignore
+    }
+  }
+
+  if (files.length === 0) {
+    console.warn("⚠️ No .ics files found for integration test.");
+    return;
+  }
+
+  console.log(`Found ${files.length} files to test.`);
+
+  for (const file of files) {
+    console.log(`  Testing file: ${file}`);
+    const text = await Deno.readTextFile(file);
+    const calendar = convertIcsCalendar(undefined, text);
+    
+    assert(calendar && calendar.events, `Failed to parse ${file}`);
+    
+    for (const icsEvent of calendar.events) {
+      if (icsEvent.status?.toUpperCase() === "CANCELLED") continue;
+
+      const finalDate = await resolveEventStart(icsEvent);
+      if (!finalDate) continue;
+      
+      const localIso = localDateString(finalDate);
+      const baseEvent = {
+        ...icsEvent,
+        name: icsEvent.summary || "Untitled Event",
+        start: localIso,
+        tag: "ical-event",
+        sourceName: "IntegrationTest"
+      };
+
+      try {
+        const expanded = expandRecurrences(baseEvent, 30);
+        assert(expanded.length >= 1, `Expected at least 1 occurrence for event "${icsEvent.summary}" in ${file}`);
+      } catch (err) {
+        console.error(`❌ Error expanding recurrence for event "${icsEvent.summary}" in ${file}:`, err);
+        throw err;
+      }
+    }
+  }
+});