fix: resolve all failing tests across utility library

src/calculator.ts

@@ -17,5 +17,6 @@ export function multiply(a: number, b: number): number {
 
 // BUG: Division by zero is not handled
 export function divide(a: number, b: number): number {
+  if (b === 0) throw new Error("Division by zero")
   return a / b
 }

src/date-utils.ts

@@ -14,7 +14,7 @@ export function formatRelative(date: Date, now: Date = new Date()): string {
   const diffSec = diffMs / 1000
   const diffMin = diffSec / 60
   const diffHours = diffMin / 60
-  const diffDays = Math.floor(diffHours / 24) // BUG: should be Math.round
+  const diffDays = Math.round(diffHours / 24)
 
   if (Math.abs(diffSec) < 60) return "just now"
   if (Math.abs(diffMin) < 60) {

src/string-utils.ts

@@ -14,7 +14,18 @@ export function reverse(str: string): string {
 // TODO: implement truncate — should truncate at a word boundary, with "..."
 // counting toward maxLength. Return unchanged if str.length <= maxLength.
 export function truncate(str: string, maxLength: number): string {
-  throw new Error("not implemented")
+  if (str.length <= maxLength) return str
+  const words = str.split(" ")
+  let result = ""
+  for (const word of words) {
+    const candidate = result ? result + " " + word : word
+    if ((candidate + "...").length <= maxLength) {
+      result = candidate
+    } else {
+      break
+    }
+  }
+  return result + "..."
 }
 
 export function slugify(str: string): string {
@@ -27,5 +38,5 @@ export function slugify(str: string): string {
 // BUG: This doesn't handle multiple consecutive spaces
 export function wordCount(str: string): number {
   if (!str.trim()) return 0
-  return str.split(" ").length
+  return str.trim().split(/\s+/).filter(Boolean).length
 }

src/task-manager.ts

@@ -52,20 +52,27 @@ export class TaskManager {
     return true
   }
 
-  // TODO: implement — remove a task by id, return true if removed, false if not found
   remove(id: string): boolean {
-    throw new Error("not implemented")
+    return this.tasks.delete(id)
   }
 
-  // TODO: implement — update title/description/priority of a task
-  // return true if updated, false if not found
   update(id: string, changes: Partial<Pick<Task, "title" | "description" | "priority">>): boolean {
-    throw new Error("not implemented")
+    const task = this.tasks.get(id)
+    if (!task) return false
+    Object.assign(task, changes)
+    return true
   }
 
-  // TODO: implement — return all tasks sorted by the given field
-  // priority sort order: high > medium > low
   sortBy(field: "priority" | "createdAt" | "status"): Task[] {
-    throw new Error("not implemented")
+    const tasks = Array.from(this.tasks.values())
+    if (field === "priority") {
+      const order: Record<Priority, number> = { high: 0, medium: 1, low: 2 }
+      return tasks.slice().sort((a, b) => order[a.priority] - order[b.priority])
+    }
+    if (field === "createdAt") {
+      return tasks.slice().sort((a, b) => a.createdAt.getTime() - b.createdAt.getTime())
+    }
+    return tasks.slice().sort((a, b) => a.status.localeCompare(b.status))
   }
+
 }

src/validator.ts

@@ -10,7 +10,7 @@
  */
 export function isEmail(value: string): boolean {
   // BUG: too restrictive — missing subdomain support and long TLDs
-  return /^[^\s@]+@[^\s@]+\.[a-zA-Z]{2,4}$/.test(value)
+  return /^[^\s@]+@[^\s@]+\.[a-zA-Z]{2,}$/.test(value)
 }
 
 /**
@@ -22,7 +22,7 @@ export function isUrl(value: string): boolean {
   try {
     const url = new URL(value)
     // BUG: only allows http/https but also rejects valid port usage
-    return (url.protocol === "http:" || url.protocol === "https:") && url.port === ""
+    return url.protocol === "http:" || url.protocol === "https:"
   } catch {
     return false
   }