/*
 * The MIT License
 * 
 * Copyright (c) 2015 schristou88
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package hudson.plugins.jira;

import hudson.model.User;
import org.junit.BeforeClass;
import org.junit.Rule;
import org.junit.Test;
import org.jvnet.hudson.test.JenkinsRule;

import java.util.Collections;

import static org.hamcrest.Matchers.*;
import static org.junit.Assert.assertThat;

/**
 * @author schristou88
 */
public class MailResolverTest extends JenkinsRule {
    @Rule
    public JenkinsRule r = new JenkinsRule();

    @BeforeClass
    public static void setUp() throws Exception {
        System.setProperty(JiraMailAddressResolver.class.getName() + ".DISABLE", "true");
    }

    @Test
    public void disableEmailResolver() {
        User user = User.get("bob", true, Collections.emptyMap());
        assertThat(JiraMailAddressResolver.resolve(user), is(nullValue()));
    }
}

Add unit test for disabling the email resolver.
Add unit test for disabling the email resolver.
