create time until methods to know how much time it left to a certain target date

src/services/time-until.test.ts

@@ -1,7 +1,68 @@
-import { describe, it, expect } from "vitest"
+import { describe, it, expect, vi, afterEach, beforeEach } from "vitest"
+import { hasPassed, timeUntil } from "./time-until"
 
-describe("time until service", () => {
-  it("test", () => {
-    expect(true).toBe(true)
+const noTime = () => ({
+  days: 0,
+  hours: 0,
+  months: 0,
+  seconds: 0,
+  years: 0,
+})
+
+describe("time until", () => {
+  beforeEach(() => {
+    vi.useFakeTimers()
+  })
+
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
+  it("tells the time until a simple target date", () => {
+    const fakeNow = new Date("2023-03-13T09:00:00.000Z")
+    vi.setSystemTime(fakeNow)
+
+    expect(timeUntil("2024-03-13T09:00:00.000Z")).toStrictEqual({
+      years: 1,
+      months: 0,
+      days: 0,
+      hours: 0,
+      seconds: 0,
+    })
+  })
+
+  it("tells the time until a more complex target date", () => {
+    const fakeNow = new Date("2023-03-13T09:00:00.000Z")
+    vi.setSystemTime(fakeNow)
+
+    expect(timeUntil("2024-02-12T19:34:22.200Z")).toStrictEqual({
+      days: 30,
+      hours: 10,
+      months: 10,
+      seconds: 2062,
+      years: 0,
+    })
+  })
+
+  it("tells 0 if the target date is passed", () => {
+    const fakeNow = new Date("2023-03-13T09:00:00.000Z")
+    vi.setSystemTime(fakeNow)
+
+    expect(timeUntil("2022-03-13T09:00:00.000Z")).toStrictEqual(noTime())
+  })
+})
+
+describe("has passed", () => {
+  it("tells if the targed has passed", () => {
+    expect(hasPassed(noTime())).toBeTruthy()
+    expect(
+      hasPassed({
+        years: 0,
+        months: 0,
+        days: 0,
+        hours: 0,
+        seconds: 1,
+      })
+    ).toBeFalsy()
   })
 })