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= Gerrit Code Review - End to end tests

This document provides descriptions of Gerrit end-to-end (`e2e`) test scenarios implemented using
the link:https://gatling.io/[Gatling,role=external,window=_blank] framework.

Similar scenarios have been successfully used to compare performance of different Gerrit versions
or study the Gerrit response under different load profiles. Although mostly for load, scenarios can
either be for link:https://gatling.io/load-testing-continuous-integration/[load or functional,role=external,window=_blank]
(e2e) testing purposes. Functional scenarios may then reuse this framework and Gatling's usability
features such as its protocols (more below) and
link:https://en.wikipedia.org/wiki/Domain-specific_language[DSL,role=external,window=_blank].

That cross test-scope reusability applies to both Gerrit core scenarios and non-core ones, such as
for Gerrit plugins or other potential extensions. End-to-end testing may then include scopes like
feature integration, deployment, smoke (and load) testing. These load and functional test scopes
should remain orthogonal to the unit and component (aka Gerrit `IT`-suffixed or `acceptance`) ones.
The term `acceptance` though may still be coined by organizations to target e2e functional testing.

== What is Gatling?

Gatling is mostly a load testing tool which provides out of the box support for the HTTP protocol.
Documentation on how to write an HTTP load test can be found
link:https://gatling.io/docs/current/http/http_protocol/[here,role=external,window=_blank].
However, in the scenarios that were initially proposed, the
link:https://github.com/GerritForge/gatling-git[Gatling Git extension,role=external,window=_blank] was
leveraged to run tests at the Git protocol level.

Gatling is written in Scala, but the abstraction provided by the Gatling DSL makes the scenarios
implementation easy even without any Scala knowledge. The
link:https://gitenterprise.me/2019/12/20/stress-your-gerrit-with-gatling/[Stress your Gerrit with Gatling,role=external,window=_blank]
blog post has more introductory information.

Examples of scenarios can be found in the `e2e-tests` directory. The files in that directory should
be formatted using the mainstream
link:https://plugins.jetbrains.com/plugin/1347-scala[Scala plugin for IntelliJ,role=external,window=_blank].
The latter is not mandatory but preferred for `sbt` and Scala IDE purposes in this project.

== How to build the tests

An link:https://www.scala-sbt.org/download.html[sbt-based installation,role=external,window=_blank]
of link:https://www.scala-lang.org/download/[Scala,role=external,window=_blank] is required.

The `scalaVersion` used by `sbt` once installed is defined in the `build.sbt` file. That specific
version of Scala is automatically used by `sbt` while building:

----
sbt compile
----

The following warning, if present when executing `sbt` commands, can be removed by creating the
link:https://www.scala-sbt.org/1.x/docs/Using-Sonatype.html#step+3%3A+Credentials[related credentials file,role=external,window=_blank]
locally. Dummy values for `user` and `password` in that file can be used initially.

----
[warn] Credentials file ~/.sbt/sonatype_credentials does not exist
----

The other warning below can be safely ignored, so far. Running the proposed `sbt evicted` command
should only list `scala-java8-compat_2.12` as `[warn]`. The other dependency conflicts should show
as `[info]`. All of the listed conflicts get usually resolved seamlessly or so.

----
[warn] There may be incompatibilities among your library dependencies; run 'evicted' to see detailed eviction warnings.
----

Every `sbt` command can include an optional log level
link:https://www.scala-sbt.org/1.x/docs/Howto-Logging.html#Change+the+logging+level+globally[argument,role=external,window=_blank].
Below, `[info]` logs are no longer shown:

----
sbt --warn compile
----

=== How to build using Docker

----
docker build . -t e2e-tests
----

== How to set-up

=== SSH keys

If you are running SSH commands, the private keys of the users used for testing need to go in
`/tmp/ssh-keys`. The keys need to be generated this way (JSch won't validate them
link:https://stackoverflow.com/questions/53134212/invalid-privatekey-when-using-jsch[otherwise,role=external,window=_blank]):

----
mkdir /tmp/ssh-keys
ssh-keygen -m PEM -t rsa -C "test@mail.com" -f /tmp/ssh-keys/id_rsa
----

The public key in `/tmp/ssh-keys/id_rsa.pub` has to be added to the test user(s) `SSH Keys` in
Gerrit. Now, the host from which the latter runs may need public key scanning to become known.
This applies to the local user that runs the forthcoming `sbt` testing commands. An example
assuming `localhost` follows:

----
ssh-keyscan -t rsa -p 29418 localhost > ~/.ssh/known_hosts
----

=== Input file

The `CloneUsingBothProtocols` scenario is fed with the data coming from the
`src/test/resources/data/com/google/gerrit/scenarios/CloneUsingBothProtocols.json` file. Such a
file contains the commands and repository used during the e2e test. That file currently looks like
below. This scenario serves as a simple example with no actual load in it. It can be used to test
or validate the local setup. More complex scenarios can be further developed, under the
`com.google.gerrit.scenarios` package. The uppercase keywords are discussed further below.

----
[
  {
    "url": "ssh://admin@HOSTNAME:SSH_PORT/_PROJECT",
    "cmd": "clone"
  },
  {
    "url": "http://HOSTNAME:HTTP_PORT/_PROJECT",
    "cmd": "clone"
  }
]
----

Valid commands are:

* `clone`
* `fetch`
* `pull`
* `push`

=== Project and HTTP credentials

The example above assumes that the `loadtest-repo` project exists in the Gerrit under test. The
`CloneUsingBothProtocols` scenario already includes creating that project and deleting it once done
with it. That scenario class can be used as an example of how a scenario can compose itself
alongside other scenarios (here, `CreateProject` and `DeleteProject`).

The `HTTP Credentials` or password obtained from test user's `Settings` (in Gerrit) may be
required, in `src/test/resources/application.conf`, depending on the above commands used. That
file's `http` section shows which shell environment variables can be used to set those credentials.

Executing the `CloneUsingBothProtocols` scenario, as is, does require setting the http credentials.
That is because of the aforementioned create/delete project (http) scenarios composed within it.

=== Environment properties

The `JAVA_OPTS` environment variable
link:https://gatling.io/docs/current/cookbook/passing_parameters[can optionally be used,role=external,window=_blank]
to define non-default values for keys found in scenario `json` data files. That variable can
currently be set with either one or many of these supported properties, from the core framework:

* `-Dcom.google.gerrit.scenarios.hostname=localhost`
* `-Dcom.google.gerrit.scenarios.ssh_port=29418`
* `-Dcom.google.gerrit.scenarios.http_port=8080`

Above, the properties can be set with values matching specific deployment topologies under test.
The example values shown above are the currently coded default ones. The framework could support
differing or more properties over time.

Plugin or otherwise non-core scenarios may do so just as well. The core java package
`com.google.gerrit.scenarios` from the example above has to be replaced with the one under which
those scenario classes are. Such extending scenarios can also add extension-specific properties.
Early examples of this can be found in the Gerrit
`link:https://gerrit.googlesource.com/plugins/high-availability[high-availability,role=external,window=_blank]`
and `link:https://gerrit.googlesource.com/plugins/multi-site[multi-site,role=external,window=_blank]`
plugins test code.

Further above, the `_PROJECT` keyword is prefixed with an underscore, which means that its value
gets automatically generated by the scenario. Any property setting for it is therefore not
applicable. Its usage differs from the non-prefixed `PROJECT` keyword, in that sense.

The following core property can be optionally set depending on the runtime environment. The test
environments used as reference for scenarios development assume its default value, `1.0`. For
slower or more complex execution environments, the value can be increased this way for example:

* `-Dcom.google.gerrit.scenarios.power_factor=1.5`

This will make the scenario steps take half more time to expect proper completion. A value smaller
than the default, say `0.8`, will make scenarios wait somewhat less than how they were developed.
Scenario development is often done using locally running Gerrit systems under test, which are
sometimes dockerized.

== How to run tests

Run all tests:
----
sbt "gatling:test"
----

Run a single test:
----
sbt "gatling:testOnly com.google.gerrit.scenarios.CloneUsingBothProtocols"
----

Generate the last report:
----
sbt "gatling:lastReport"
----

The `src/test/resources/logback.xml` file
link:http://logback.qos.ch/manual/configuration.html[configures,role=external,window=_blank]
Gatling's logging level. To quickly enable
link:https://gatling.io/docs/current/general/debugging#logback[detailed logging,role=external,window=_blank]
of `http` requests and responses, the `root level` can be set to `trace` in that file.

=== How to run using Docker

----
docker run -it e2e-tests -s com.google.gerrit.scenarios.CloneUsingBothProtocols
----

=== How to run non-core scenarios

Locally adding non-core scenarios, for example from Gerrit plugins, is as simple as copying such
files in. Copying is necessary over linking, unless running using Docker (above) is not required.
Docker does not support links for files it has to copy over through the Dockerfile (here, the
scenario files). Here is how to proceed for adding such external (e.g., plugin) scenario files in:

----
pushd e2e-tests/src/test/scala
cp -r (or, ln -s) scalaPackageStructure .
popd

pushd e2e-tests/src/test/resources/data
cp -r (or, ln -s) jsonFilesPackageStructure .
popd
----

The destination folders above readily git-ignore every non-core scenario file added under them. If
running using Docker, `e2e-tests/Dockerfile` may require another `COPY` line for the hereby added
scenarios. Aforementioned `sbt` or `docker` commands can then be used to run the added tests.

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