nip13: add minePow function

nip13.test.ts

@@ -1,7 +1,21 @@
-import { getPow } from './nip13.ts'
+import { getPow, minePow } from './nip13.ts'
 
 test('identifies proof-of-work difficulty', async () => {
   const id = '000006d8c378af1779d2feebc7603a125d99eca0ccf1085959b307f64e5dd358'
   const difficulty = getPow(id)
   expect(difficulty).toEqual(21)
 })
+
+test('mines POW for an event', async () => {
+  const difficulty = 10
+
+  const event = minePow({
+    kind: 1,
+    tags: [],
+    content: 'Hello, world!',
+    created_at: 0,
+    pubkey: '79c2cae114ea28a981e7559b4fe7854a473521a8d22a66bbab9fa248eb820ff6',
+  }, difficulty)
+
+  expect(getPow(event.id)).toBeGreaterThanOrEqual(difficulty)
+})