[[ci]]
== Continuous integration

Erlang.mk comes with some support for continuous integration,
aimed at open source projects that need to support more than
one specific Erlang/OTP release. (If you target one specific
release, check the xref:otp_version_pinning[OTP version pinning]
section of the xref:kerl[OTP version management] chapter.)

=== Configuring Erlang/OTP versions to test

To use the CI plugin you must first configure which versions
of Erlang/OTP will be used. Erlang.mk provides three separate
configuration variables depending on whether you need a normal
OTP release, a HiPE-enabled release or an ErLLVM-enabled release.

At the time of writing, this is how you would test against all
the most recent patch releases of Erlang/OTP 19 and above:

[source,make]
CI_OTP = OTP-19.0.7 OTP-19.1.6 OTP-19.2.3 OTP-19.3.6.2 OTP-20.0.4

If you want to test against HiPE and ErLLVM but only with the
latest version of Erlang/OTP, the following could work:

[source,make]
CI_HIPE = $(lastword $(CI_OTP))
CI_ERLLVM = $(CI_HIPE)

Consult the xref:kerl[OTP version management] chapter for more
information about Erlang/OTP versions and customization of the
Erlang/OTP builds.

=== Running tests across all configured versions

The recommended way to run the `ci` target is with the option
`-k`. It will ensure that tests are run for all configured
Erlang/OTP versions, even if there are errors:

[source,bash]
$ make ci -k

=== Extending the CI targets

The `ci` target can be extended. For example to run Dialyzer
at the end of CI:

[source,make]
----
ci:: dialyze
----

Additional setup can be done by extending the `ci-setup`
target. This target is ran before testing each individual
Erlang/OTP version.

For example, to ensure dependencies are re-fetched/built
before testing individual Erlang/OTP releases:

[source,make]
----
ci-setup:: distclean
----

Similarly, the `ci-extra` target can be extended to run
extra commands after an Erlang/OTP version has been tested.