add test case for type check

Author: grindcode

test/types.js

@@ -0,0 +1,16 @@
+var test = require('tape')
+var inject = require('../index.js')
+
+test('invalid first argument', function (t) {
+  t.plan(1)
+  t.throws(function () {
+    var result = inject({ is: 'object' }, 'try', 1)
+  })
+})
+
+test('invalid third argument', function (t) {
+  t.plan(1)
+  t.throws(function () {
+    var result = inject('validstring', 'try', 'index')
+  })
+})