Add save DHT state test

package.json

@@ -86,6 +86,7 @@
     "serve-static": "^1.11.1",
     "standard": "*",
     "tape": "^4.6.0",
+    "tmp": "0.0.33",
     "webtorrent-fixtures": "^1.5.0"
   },
   "engines": {

test/node/persist-dht-nodes.js

@@ -0,0 +1,41 @@
+var test = require('tape')
+var tmp = require('tmp')
+var fs = require('fs')
+var DHT = require('bittorrent-dht/server')
+var WebTorrent = require('../../')
+
+var localHost = '127.0.0.1'
+var port = 9999
+
+test('Save DHT state', function (t) {
+  t.plan(4)
+  var saveFile = tmp.tmpNameSync()
+  var dhtServer = new DHT({ bootstrap: false })
+  dhtServer.on('error', function (err) { t.fail(err) })
+  dhtServer.on('warning', function (err) { t.fail(err) })
+  dhtServer.listen(port, function handleServerListening () {
+    var client = new WebTorrent({
+      dht: { bootstrap: false },
+      dhtState: saveFile
+    })
+    client.on('error', function (err) { t.fail(err) })
+    client.on('warning', function (err) { t.fail(err) })
+    client.dht.addNode({ host: localHost, port: port })
+    client.dht.on('node', function handleNodeAdded () {
+      client.saveDhtState(function handleDhtStateSaved () {
+        var dhtStateJson = fs.readFileSync(saveFile)
+        var dhtState = JSON.parse(dhtStateJson)
+        var nodes = dhtState.nodes
+        var node = nodes[0]
+        t.equal(node.host, localHost)
+        t.equal(node.port, port)
+        client.destroy(function handleClientDestroyed (err) {
+          t.error(err, 'client destroyed')
+        })
+        dhtServer.destroy(function handleDhtServerDestroyed (err) {
+          t.error(err, 'dht server destroyed')
+        })
+      })
+    })
+  })
+})