add a bunch of tests.

keys.test.js

@@ -0,0 +1,20 @@
+/* eslint-env jest */
+
+const {generatePrivateKey, getPublicKey} = require('./cjs')
+
+test('test private key generation', () => {
+  expect(generatePrivateKey()).toMatch(/[a-f0-9]{64}/)
+})
+
+test('test public key generation', () => {
+  expect(getPublicKey(generatePrivateKey())).toMatch(/[a-f0-9]{64}/)
+})
+
+test('test public key from private key deterministic', () => {
+  let sk = generatePrivateKey()
+  let pk = getPublicKey(sk)
+
+  for (let i = 0; i < 5; i++) {
+    expect(getPublicKey(sk)).toEqual(pk)
+  }
+})