feat: ✨ Add the Extends type - Check if one type extends from another

.changeset/heavy-feet-sin.md

@@ -0,0 +1,5 @@
+---
+"@crbroughton/ts-test-utils": minor
+---
+
+Add the Extends type - Check if one type extends from another

index.ts

@@ -7,3 +7,5 @@ export type Includes<T extends U, U> = T extends U ? true : false
 export type Excludes<T, U> = [T] extends [U] ? false : true
 
 export type Assignable<T, U extends T> = U extends T ? true : false
+
+export type Extends<T, U> = U extends T ? true : false

tests/Extends.test.ts

@@ -0,0 +1,20 @@
+/* eslint-disable unused-imports/no-unused-vars */
+import { describe, it } from 'bun:test'
+import type { Expect, Extends } from '..'
+
+describe('Extends tests', () => {
+  it('Passes the extend test when the resulting type extends another type', () => {
+    interface BaseType { id: number }
+    type ExtensionType = BaseType & { name: string }
+    type Result = Expect<Extends<BaseType, ExtensionType>>
+    //   ^?
+  })
+  it('Failed the includes test when the resulting type does not include the sub-type', () => {
+    // @ts-expect-error - Object / Record failing the equality checker
+    type Result = Expect<Includes<{ id: number, name: string }, { hobby: string }>>
+    //   ^?
+  })
+})
+
+
+