Apex Test function for creating new users.

ApexTestUserUtils.java

@isTest
private class MyTestClass {

    @isTest
    static void test_something() {

        Profile p = [ SELECT id FROM Profile WHERE name = 'Standard User' ];

        User user1, user2;

        // https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_testing_tools_runas.htm
        System.runAs( new User( id = UserInfo.getUserId() ) ) {

            user1 = newUser( p.id, 'Alpha', 'User 1', '[email protected]' );
            user2 = newUser( p.id, 'Beta',  'User 2', '[email protected]' );

            insert new List<User>{ user1, user2 };

        }
        
        // TODO

    }

    private static User newUser( ID profileId, String firstName, String lastName, String email ) {
        Integer rand = Math.round( Math.random() * 1000 );
        return new User(
            isActive = true,
            profileId = profileId,
            alias = firstName.substring(0,1) + lastName.substring(1,5),
            firstName = firstName,
            lastName = lastName,
            email = email,
            username = rand + email,
            emailEncodingKey = 'UTF-8',
            languageLocaleKey = 'en_US',
            localeSidKey = 'en_US',
            timeZoneSidKey = 'America/Chicago'
        );
    }
    
}