test: strengthen LRU eviction test with key-level assertions

Bortlesboat · Bortlesboat · commit 00cb426b2c66 · 2026-03-08T06:25:30.000-04:00
Add hasCronInCacheForTest helper and assert specific cache entries
survive or get evicted. The test now fails under FIFO but passes
under LRU, directly verifying the promotion behavior.
diff --git a/src/cron/schedule.test.ts b/src/cron/schedule.test.ts
@@ -5,6 +5,7 @@ import {
   computeNextRunAtMs,
   computePreviousRunAtMs,
   getCronScheduleCacheSizeForTest,
+  hasCronInCacheForTest,
 } from "./schedule.js";
 
 describe("cron schedule", () => {
@@ -147,7 +148,8 @@ describe("cron schedule", () => {
   it("promotes accessed entries to avoid premature LRU eviction", () => {
     const nowMs = Date.parse("2026-03-01T00:00:00.000Z");
 
-    // Fill cache to capacity with unique expressions
+    // Fill cache to capacity with unique expressions.
+    // i=0 → "0 0 * * *", i=1 → "1 0 * * *", ..., i=511 → "31 8 * * *"
     for (let i = 0; i < 512; i++) {
       computeNextRunAtMs(
         { kind: "cron", expr: `${i % 60} ${Math.floor(i / 60)} * * *`, tz: "UTC" },
@@ -156,18 +158,23 @@ describe("cron schedule", () => {
     }
     expect(getCronScheduleCacheSizeForTest()).toBe(512);
 
-    // Access the very first entry so it gets promoted (LRU touch)
+    // Entry #0 ("0 0 * * *") is the oldest by insertion order.
+    // Access it so LRU promotes it (delete + re-insert at end of Map).
     computeNextRunAtMs({ kind: "cron", expr: "0 0 * * *", tz: "UTC" }, nowMs);
 
-    // Insert a new entry — this should evict the second-oldest, not the first
+    // Entry #1 ("1 0 * * *") is now the least-recently-used.
+    // Insert a new entry to trigger one eviction.
     computeNextRunAtMs({ kind: "cron", expr: "0 0 1 1 *", tz: "UTC" }, nowMs);
     expect(getCronScheduleCacheSizeForTest()).toBe(512);
 
-    // The first entry should still be cached (was promoted).
-    // Insert another new entry — if FIFO, the first entry would now be evicted.
-    // With LRU, the third-oldest entry is evicted instead.
-    computeNextRunAtMs({ kind: "cron", expr: "0 0 2 1 *", tz: "UTC" }, nowMs);
-    expect(getCronScheduleCacheSizeForTest()).toBe(512);
+    // Under LRU: entry #0 survived (was promoted), entry #1 was evicted.
+    // Under FIFO: entry #0 would be evicted instead — this assertion would fail.
+    expect(hasCronInCacheForTest("0 0 * * *", "UTC")).toBe(true);
+    expect(hasCronInCacheForTest("1 0 * * *", "UTC")).toBe(false);
+
+    // The new entry and a non-evicted middle entry should both be present.
+    expect(hasCronInCacheForTest("0 0 1 1 *", "UTC")).toBe(true);
+    expect(hasCronInCacheForTest("2 0 * * *", "UTC")).toBe(true);
   });
 
   describe("cron with specific seconds (6-field pattern)", () => {
diff --git a/src/cron/schedule.ts b/src/cron/schedule.ts
@@ -171,3 +171,7 @@ export function clearCronScheduleCacheForTest(): void {
 export function getCronScheduleCacheSizeForTest(): number {
   return cronEvalCache.size;
 }
+
+export function hasCronInCacheForTest(expr: string, tz: string): boolean {
+  return cronEvalCache.has(`${tz}\u0000${expr}`);
+}

Original file line number	Diff line number	Diff line change
`@@ -171,3 +171,7 @@ export function clearCronScheduleCacheForTest(): void {`
`171`	`171`	`export function getCronScheduleCacheSizeForTest(): number {`
`172`	`172`	`return cronEvalCache.size;`
`173`	`173`	`}`
	`174`	`+`
	`175`	`+export function hasCronInCacheForTest(expr: string, tz: string): boolean {`
	`176`	+ return cronEvalCache.has(`${tz}\u0000${expr}`);
	`177`	`+}`