refactored snippet dataApi for easy testing and added some test. Fixed old snippet still display when deleted

tests/dataApi/updateSnippet-test.js

@@ -0,0 +1,48 @@
+const test = require('ava')
+const updateSnippet = require('browser/main/lib/dataApi/updateSnippet')
+const sander = require('sander')
+const os = require('os')
+const path = require('path')
+const crypto = require('crypto')
+
+const snippetFilePath = path.join(os.tmpdir(), `test${path.sep}update-snippet`)
+const snippetFile = path.join(snippetFilePath, 'snippets.json')
+const oldSnippet = {
+  id: crypto.randomBytes(16).toString('hex'),
+  name: 'Initial snippet',
+  prefix: [],
+  content: ''
+}
+
+const newSnippet = {
+  id: oldSnippet.id,
+  name: 'new name',
+  prefix: ['prefix'],
+  content: 'new content'
+}
+
+
+test.beforeEach((t) => {
+  sander.writeFileSync(snippetFile, JSON.stringify([oldSnippet]))
+})
+
+test.serial('Update a snippet', (t) => {
+  return Promise.resolve()
+    .then(function doTest () {
+      return Promise.all([
+        updateSnippet(newSnippet, snippetFile)
+      ])
+    })
+    .then(function assert () {
+      const snippets = JSON.parse(sander.readFileSync(snippetFile))
+      const snippet = snippets.find(currentSnippet => currentSnippet.id === newSnippet.id)
+      t.not(snippet, undefined)
+      t.is(snippet.name, newSnippet.name)
+      t.deepEqual(snippet.prefix, newSnippet.prefix)
+      t.is(snippet.content, newSnippet.content)
+    })
+})
+
+test.after.always(() => {
+  sander.rimrafSync(snippetFilePath)
+})