From a1ca1ff81572fa7f50380186ac324ef24a4eaf54 Mon Sep 17 00:00:00 2001
From: CRBroughton <crbroughton@posteo.uk>
Date: Sun, 21 Apr 2024 16:39:44 +0100
Subject: [PATCH] feat: :sparkles: Add the Length type - Check a given types
 length

---
 .changeset/red-apples-grow.md |  5 +++++
 index.ts                      |  2 ++
 tests/Length.test.ts          | 20 ++++++++++++++++++++
 3 files changed, 27 insertions(+)
 create mode 100644 .changeset/red-apples-grow.md
 create mode 100644 tests/Length.test.ts

diff --git a/.changeset/red-apples-grow.md b/.changeset/red-apples-grow.md
new file mode 100644
index 0000000..8dfb121
--- /dev/null
+++ b/.changeset/red-apples-grow.md
@@ -0,0 +1,5 @@
+---
+"@crbroughton/ts-test-utils": minor
+---
+
+Add the Length type - Check a given types length
diff --git a/index.ts b/index.ts
index e7465b5..7a5fd97 100644
--- a/index.ts
+++ b/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']
diff --git a/tests/Length.test.ts b/tests/Length.test.ts
new file mode 100644
index 0000000..d998df5
--- /dev/null
+++ b/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>>
+    //   ^?
+  })
+})