add Jest suite from vue-cli-3 branch

tests/helpers.js

@@ -0,0 +1,28 @@
+import { shallowMount } from "@vue/test-utils";
+import VueSelect from "../src/components/Select";
+
+/**
+ * Trigger a submit event on the search
+ * input with a provided search text.
+ *
+ * @param Wrapper {Wrapper<Vue>}
+ * @param searchText
+ */
+export const searchSubmit = (Wrapper, searchText = false) => {
+  if (searchText) {
+    Wrapper.vm.search = searchText;
+  }
+  Wrapper.find({ ref: "search" }).trigger("keydown", {
+    keyCode: 13
+  });
+};
+
+/**
+ * Create a new VueSelect instance with
+ * a provided set of props.
+ * @param propsData
+ * @returns {Wrapper<Vue>}
+ */
+export const selectWithProps = (propsData = {}) => {
+  return shallowMount(VueSelect, { propsData });
+};