initial

packages/shared/src/day-boundary.test.ts

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+import { describe, it, expect } from "vitest";
+import {
+  getLogicalToday,
+  getLogicalYesterday,
+  isWithinGraceWindow,
+} from "./day-boundary";
+
+describe("day-boundary", () => {
+  it("returns calendar date when boundary is midnight and after noon", () => {
+    const now = new Date(2026, 5, 26, 14, 0, 0);
+    expect(getLogicalToday(0, now)).toBe("2026-06-26");
+  });
+
+  it("returns previous calendar date when before boundary hour", () => {
+    const now = new Date(2026, 5, 26, 1, 30, 0);
+    expect(getLogicalToday(2, now)).toBe("2026-06-25");
+  });
+
+  it("returns current date when at or after boundary hour", () => {
+    const now = new Date(2026, 5, 26, 2, 30, 0);
+    expect(getLogicalToday(2, now)).toBe("2026-06-26");
+  });
+
+  it("computes logical yesterday", () => {
+    const now = new Date(2026, 5, 26, 14, 0, 0);
+    expect(getLogicalYesterday(0, now)).toBe("2026-06-25");
+  });
+
+  it("detects grace window after midnight", () => {
+    const now = new Date(2026, 5, 26, 1, 0, 0);
+    expect(isWithinGraceWindow(0, 4, now)).toBe(true);
+  });
+
+  it("is outside grace window mid-day", () => {
+    const now = new Date(2026, 5, 26, 14, 0, 0);
+    expect(isWithinGraceWindow(0, 4, now)).toBe(false);
+  });
+});