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src/lib/latest.test.ts

@@ -0,0 +1,33 @@
+import { describe, expect, it } from "vitest";
+import { tickets } from "./latest";
+
+describe("tickets", () => {
+  it("treats the only ticket taken as the newest", () => {
+    const t = tickets();
+    const a = t.take();
+    expect(t.isLatest(a)).toBe(true);
+  });
+  it("treats an older ticket as out of date once a newer one is taken", () => {
+    const t = tickets();
+    const older = t.take();
+    const newer = t.take();
+    expect(t.isLatest(older)).toBe(false);
+    expect(t.isLatest(newer)).toBe(true);
+  });
+  it("keeps an older ticket out of date after more tickets are taken", () => {
+    const t = tickets();
+    const first = t.take();
+    t.take();
+    const last = t.take();
+    expect(t.isLatest(first)).toBe(false);
+    expect(t.isLatest(last)).toBe(true);
+  });
+  it("keeps separate sets of tickets apart", () => {
+    const a = tickets();
+    const b = tickets();
+    const fromA = a.take();
+    b.take();
+    b.take();
+    expect(a.isLatest(fromA)).toBe(true);
+  });
+});