feat: ✨ Add the Length type - Check a given types length

.changeset/red-apples-grow.md

@@ -0,0 +1,5 @@
+---
+"@crbroughton/ts-test-utils": minor
+---
+
+Add the Length type - Check a given types length

index.ts

@@ -15,3 +15,5 @@ export type Extends<T, U> = U extends T ? true : false
 export type isArray<T> = T extends any[] ? true : false
 
 export type isNonArray<T> = isArray<T> extends true ? false : true
+
+export type Length<T extends readonly any[]> = T['length']

tests/Length.test.ts

@@ -0,0 +1,20 @@
+/* eslint-disable unused-imports/no-unused-vars */
+import { describe, it } from 'bun:test'
+import type { Equals, Expect, Length } from '../index'
+
+describe('Length tests', () => {
+  it('Passes the length test when the lengths dont match', () => {
+    type Result = Expect<Equals<Length<[0, 1, 2]>, 3>>
+    //   ^?
+    type ResultRecord = Expect<Equals<Length<[{ id: string }, { name: string }]>, 2>>
+    //   ^?
+  })
+  it('Fails the length test when the types are not of the same length', () => {
+    // @ts-expect-error - number values failing the length checker
+    type Results = Expect<Equals<Length<[0, 1, 2]>, 10>>
+    //   ^?
+    // @ts-expect-error - Object / Record failing the length checker
+    type ResultRecord = Expect<Equals<Length<[{ id: string }, { name: string }]>, 10>>
+    //   ^?
+  })
+})