Add specs for User#is_admin?

spec/models/user_spec.rb

@@ -1,5 +1,23 @@
 require 'rails_helper'
 
 RSpec.describe User, type: :model do
-  pending "add some examples to (or delete) #{__FILE__}"
+  let(:user) { create :user }
+
+  describe "#is_admin?" do
+    it "returns true when admin flag is set in LDAP" do
+      expect(Devise::LDAP::Adapter).to receive(:get_ldap_param)
+        .with(user.cn, :admin)
+        .and_return("true")
+
+      expect(user.is_admin?).to be true
+    end
+
+    it "returns false when admin flag is not set in LDAP" do
+      expect(Devise::LDAP::Adapter).to receive(:get_ldap_param)
+        .with(user.cn, :admin)
+        .and_return(nil)
+
+      expect(user.is_admin?).to be false
+    end
+  end
 end