In order for the creation of a temporary directory to install plugins
into to be simpler to understand and use, we change how the directory is
created, cleaned-up, and installs plugins into.
Now, instead of a tuple of a string (path) and a cleanup function, we
return a structure that comprises the test suite, and the temporary
directory, along with methods to handle those steps independently.
The lib name for the common components for writing packer_test suites
was not clear, and did not follow the convention established in Packer
core and plugins.
Therefore this commit does two things: first the lib is renamed into
common as to follow this convention, and clearly document which
components are common to all tests.
Also checkers are placed in a subpackage of common, common/check, so
that it is clearer what is meant to be used as checks for a command's
execution status after it's been run, as part of Assert.
The function's name was the same as the plugins test suite runner/init
function, making it impossible to differentiate between the two when
looking at the logs, or when attempting to filter which tests to run
using the suite function's name.
Having only one test suite for the whole of Packer makes it harder to
segregate between test types, and makes for a longer runtime as no tests
run in parallel by default.
This commit splits the packer_test suite into several components in
order to make extension easier.
First we have `lib`: this package embeds the core for running Packer
test suites. This ships facilities to build your own test suite for
Packer core, and exposes convenience methods and structures for building
plugins, packer core, and use it to run a test suite in a temporary
directory.
Then we have two separate test suites: one for plugins, and one for core
itself, the latter of which does not depend on plugins being compiled at
all.
This sets the stage for more specialised test suites in the future, each
of which can run in parallel on different parts of the code.
