samba-mirror/selftest/target

Selftest target environments (testenvs)
=======================================
Samba's integration testing heavily relies on the automatic creation of a Samba
network. This specialized test environment is generally referred to as a Samba
'testenv'.

A testenv involves starting the Samba server listening on a fake network, which
is established using the socket_wrapper library from cwrap (https://cwrap.org).
All testing is also done as a non-root user using the uid_wrapper library, also
from cwrap.

Samba's test framework uses many different types of testenv. Each testenv is
customized to test a particular Samba feature or configuration. Using cwrap
allows multiple different Samba servers to run at the same time, without
interference.

Some of the different testenvs are described in more detail below.

Backup/restore testenvs
-----------------------
Several testenvs are created to test the domain backup/restore commands. These
testenvs verify that we can backup and restore a domain's database, start
Samba against it, and the restored database is actually functional. There are
several different flavours of backups (to cover different use-cases), so there
are separate testenvs for each one.

- backupfromdc: A fairly plain AD DC used as the base to generate the
    backup-files. These backup-files will then seed the domain database
    for the separate testenvs below.
    Backupfromdc's other unique feature is that it's the only testenv that gets
    provisioned with a non-default site, i.e. Default-First-Site-Name doesn't
    exist.
- restoredc: tests the 'backup online' option. Online backups are similar to
    doing a DC join.
- offlinebackupdc: tests the 'backup offline' option. Offline backups capture
    the raw DB files on disk (safely).
- renamedc: tests the 'backup rename' option, where the domain and realm are
    renamed.
- labdc: one of the use-cases for the backup tool is to create a realistic
    pre-production testbed, based off a production DC. This testenv simulates
    that process. It uses the 'backup rename --no-secrets' option.

customdc testenv
----------------
The customdc is a special testenv that's only used for manual testing, rather
than the automated tests most testenvs are primarily used for.

The customdc testenv also uses the backup/restore tool, however, it is quite
special. Instead of the backup-file being automatically generated from a
vanilla AD DC (i.e. backupfromdc), you can specify any backup-file you like.

To run the testenv, you need to specify a 'BACKUP_FILE' shell variable, e.g.

BACKUP_FILE=/tmp/samba-backup-50k-dc-0-mdb-50k-offline.tar.bz2 \
    SELFTEST_TESTENV=customdc make testenv

The main use-case for the customdc is testing changes against a large
database. Adding users is very time-consuming, so it's much quicker to populate
a domain with users once, take a backup, and then you can spin up a testenv
based on the backup multiple times.

Another use-case is that if you get a database that's corrupted or in a bad
state, then you could save a backup and be able to easily get the database back
into the bad state. This allows you to try different commands to diagnose/fix
the issue, without fear of never seeing the problem again.

You could even spin up a 'lab DC' inside a testenv, by taking a backup of a
real network DC.