Each Builder is equipped with a “build factory”, which is
responsible for producing the actual Build objects that perform
each build. This factory is created in the configuration file, and
attached to a Builder through the factory element of its
dictionary.
The standard BuildFactory object creates Build objects
by default. These Builds will each execute a collection of BuildSteps
in a fixed sequence. Each step can affect the results of the build,
but in general there is little intelligence to tie the different steps
together.
The steps used by these builds are all subclasses of BuildStep.
The standard ones provided with Buildbot are documented later,
See Build Steps. You can also write your own subclasses to use in
builds.
The basic behavior for a BuildStep is to: