refactor: ping (#505)

* refactor: ping

* chore: ping is now a function

* chore: address review

test/core/ping.node.js

@@ -0,0 +1,35 @@
+'use strict'
+/* eslint-env mocha */
+
+const chai = require('chai')
+chai.use(require('dirty-chai'))
+const { expect } = chai
+
+const pTimes = require('p-times')
+
+const peerUtils = require('../utils/creators/peer')
+const baseOptions = require('../utils/base-options')
+
+describe('ping', () => {
+  let nodes
+
+  beforeEach(async () => {
+    nodes = await peerUtils.createPeer({
+      number: 2,
+      config: baseOptions
+    })
+  })
+
+  it('ping once from peer0 to peer1', async () => {
+    const latency = await nodes[0].ping(nodes[1].peerInfo)
+
+    expect(latency).to.be.a('Number')
+  })
+
+  it('ping several times for getting an average', async () => {
+    const latencies = await pTimes(5, () => nodes[1].ping(nodes[0].peerInfo))
+
+    const averageLatency = latencies.reduce((p, c) => p + c, 0) / latencies.length
+    expect(averageLatency).to.be.a('Number')
+  })
+})