test(curriculum): use Mocha for tests

curriculum/test/utils/mongoIds.js

@@ -0,0 +1,24 @@
+const _ = require('lodash');
+const { isMongoId } = require('validator');
+
+class MongoIds {
+  constructor() {
+    this.knownIds = [];
+  }
+  check(id, title) {
+    if (!isMongoId(id)) {
+      throw new Error(`Expected a valid ObjectId for ${title}, but got ${id}`);
+    }
+    const idIndex = _.findIndex(this.knownIds, existing => id === existing);
+    if (idIndex !== -1) {
+      throw new Error(`
+    All challenges must have a unique id.
+
+    The id for ${title} is already assigned
+    `);
+    }
+    this.knownIds = [ ...this.knownIds, id ];
+  }
+}
+
+module.exports = MongoIds;