increase sync.js internal coverage

lib/async.js

@@ -65,19 +65,13 @@ function resolvePromise (promise, callback) {
   })
 }
 module.exports = function (password, salt, iterations, keylen, digest, callback) {
-  checkParameters(password, salt, iterations, keylen)
-
-  if (!Buffer.isBuffer(password)) password = Buffer.from(password, defaultEncoding)
-  if (!Buffer.isBuffer(salt)) salt = Buffer.from(salt, defaultEncoding)
-
   if (typeof digest === 'function') {
     callback = digest
     digest = undefined
   }
-  if (typeof callback !== 'function') throw new Error('No callback provided to pbkdf2')
-
   digest = digest || 'sha1'
   var algo = toBrowser[digest.toLowerCase()]
+
   if (!algo || typeof global.Promise !== 'function') {
     return process.nextTick(function () {
       var out
@@ -89,6 +83,12 @@ module.exports = function (password, salt, iterations, keylen, digest, callback)
       callback(null, out)
     })
   }
+
+  checkParameters(password, salt, iterations, keylen)
+  if (typeof callback !== 'function') throw new Error('No callback provided to pbkdf2')
+  if (!Buffer.isBuffer(password)) password = Buffer.from(password, defaultEncoding)
+  if (!Buffer.isBuffer(salt)) salt = Buffer.from(salt, defaultEncoding)
+
   resolvePromise(checkNative(algo).then(function (resp) {
     if (resp) {
       return browserPbkdf2(password, salt, iterations, keylen, algo)

package.json

@@ -30,6 +30,8 @@
   },
   "scripts": {
     "prepublish": "npm run test",
+    "coverage-report": "nyc report --reporter=lcov",
+    "coverage-html": "nyc report --reporter=html",
     "coverage": "nyc --check-coverage --branches 90 --functions 100 tape test/*.js",
     "lint": "standard",
     "test": "npm run lint && npm run unit",