:page-layout: basic

= Testing

Creating tests is one of the most important and also most difficult
parts of developing Cassandra. There are different ways to test your
code depending on what you're working on.

Cassandra tests can be divided into three main categories, based on the
way how they are executed:

* *<<java_tests>>* - tests implemented in Java and being a part of the
Cassandra project. You can distinguish the following subcategories there:

** *<<junit_tests>>* - consists of unit tests, single-node integration
tests and some tool tests; those tests may run a server with limited
functionality in the same JVM as the test code

** *<<jvm_distributed_tests>>* - integrated tests against one or multiple
nodes, each running in their own classloader; also contains upgrade
tests

** *<<microbenchmarks>>* - micro-benchmarks implemented with
https://github.com/openjdk/jmh[JMH framework]

* *<<cqlsh_tests>>* - CQLSH tests are Python tests written with the Nose
test framework. They verify the CQLSH client that can be found in the
bin directory. They aim at verifying CQLSH specific behavior like output
formatting, autocompletion, parsing, etc).

* *<<python_dtests>>* - Python distributed tests are
implemented on top of the PyTest framework and located outside the main
Cassandra project in the separate repository
https://github.com/apache/cassandra-dtest[apache/cassandra-dtest]. They
test Cassandra via https://github.com/riptano/ccm[CCM] verifying
operation results, logs, and cluster state. Python Distributed tests are
Cassandra version agnostic. They include upgrade tests.

In case you want to run DTests with your own version of CCM, please refer to requirements.txt in
https://github.com/apache/cassandra-dtest[apache/cassandra-dtest] how to do it.

The recipes for running those tests can be found in the cassandra-builds repository https://github.com/apache/cassandra-builds/tree/trunk/build-scripts[here].

Running full test suites locally takes hours, if not days. Beyond running specific tests you know are applicable, or are failing, to the work at hand, it is recommended to rely upon the project's https://cassandra.apache.org/_/development/ci.html[Continuous Integration systems]. If you are not a committer, and don't have access to a premium CircleCI plan, ask one of the committers to test your patch on the project's https://ci-cassandra.apache.org/[ci-cassandra.apache.org].

[#java_tests]
== Java tests

The simplest test to write for Cassandra code is a unit test. Cassandra
uses JUnit as a testing framework and test cases can be found in the
`test/unit` directory. Ideally, you’ll create a unit test for
your implementation that exclusively covers the class you created
(the unit under test).

Unfortunately, this is not always possible, because Cassandra doesn't
have a very mock friendly code base. Often you’ll find yourself in a
situation where you have to use the embedded Cassandra instance to
interact with your test. If you want to use CQL in your test,
you can extend CQLTester and use some convenient helper methods, as
shown here:

[source,java]
----
@Test
public void testBatchAndList() throws Throwable
{
   createTable("CREATE TABLE %s (k int PRIMARY KEY, l list<int>)");
   execute("BEGIN BATCH " +
           "UPDATE %1$s SET l = l +[ 1 ] WHERE k = 0; " +
           "UPDATE %1$s SET l = l + [ 2 ] WHERE k = 0; " +
           "UPDATE %1$s SET l = l + [ 3 ] WHERE k = 0; " +
           "APPLY BATCH");

   assertRows(execute("SELECT l FROM %s WHERE k = 0"),
              row(list(1, 2, 3)));
}
----

[#junit_tests]
=== JUnit tests

To run the unit tests:

[source,none]
----
ant test
----

However, this is probably not what you want to do, since that
command would run all the unit tests (those from `test/unit`). It would
take about an hour or more to finish.

To run the specific test class or even a method, use the following
command:

[source,none]
----
ant testsome -Dtest.name=<TestClassName> -Dtest.methods=<testMethodName>
----

* `test.name` property is for either a simple or fully qualified class
name
* `test.methods` property is optional; if not specified, all test cases
from the specified class are executed. Though, you can also specify
multiple methods separating them by comma

You can also use the IDE to run the tests - when you generate IDE files and
properly import the Cassandra project, you can run the
tests by right-clicking on the test class or package name. Remember that
it is not enough to compile with IDE for some tests, and you need to
call `ant jar` to build the distribution artifacts. When
the test runs some tool as an external process, the tool expects
Cassandra artifacts to be in the build directory.

Note that those commands apply to the tests in the `test/unit`
directory. There are, however, some other test categories that have
tests in individual directories:

* `test/burn` - to run them, call  `ant test-burn` or
`ant burn-testsome`;
`ant burn-test-jar` builds a self-contained jar for e.g. remote execution; not currently
used for running burn tests in our scripts. `ant burn-test-jar` exists only on 4.0+ branches
* `test/long` - to run them, call `ant long-test` or `ant long-testsome`
* `test/memory` - to run them, call `ant test-memory`
* `test/microbench` discussed in <<microbenchmarks>>
* `test/distributed` discussed in <<jvm_distributed_tests>>

[TIP]
.Hint
====
If you get the error similar to the one below, install the
`ant-optional` package
because you need the `JUnitTask` class
(see xref:development/ide.adoc[prerequisites]).

[source,none]
----
Throws: cassandra-trunk/build.xml:1134: taskdef A class needed by class org.krummas.junit.JStackJUnitTask cannot be found:
org/apache/tools/ant/taskdefs/optional/junit/JUnitTask  using the classloader
AntClassLoader[/.../cassandra-trunk/lib/jstackjunit-0.0.1.jar]
----
====

[#stress_and_fqltool_tests]
=== Stress and FQLTool tests

_Stress_ and _FQLTool_ are separate modules located under the `tools`
directory in the Cassandra project. They have their own source code and
unit tests. To run the tests for those tools, first, build jar artifacts
for them by calling:

[source,]
----
ant fqltool-build fqltool-build-test
ant stress-build stress-build-test
----

Then you can execute the tests with either one of the commands:

[source,plaintext]
----
ant fqltool-test
ant stress-test
and stress-test-some
----

or using your IDE.

[#jvm_distributed_tests]
=== JVM distributed tests

JVM distributed tests can run a cluster of nodes inside a single JVM -
they utilize a particular framework (that can be found at
https://github.com/apache/cassandra-in-jvm-dtest-api[apache/cassandra-in-jvm-dtest-api])
for that purpose. Those tests are intended to test features that require
more started nodes or verify specific behaviors when the nodes get
restarted, including upgrading them from one version to another. The
tests are located at the `test/distributed` directory of the Cassandra
project; however, only `org.apache.cassandra.distributed.test` and
`org.apache.cassandra.upgrade` packages contain the actual tests. The
rest of the files are various utilities related to the distributed test
framework.

The distributed tests can be run in few ways. `ant test-jvm-dtest`
command runs all the distributed JVM tests. It is not very useful; thus,
there is also `ant test-jvm-dtest-some`, which allows specifying test
class and test name in the similar way as you could do that for the
`ant testsome` command, for example:

[source,plaintext]
----
ant test-jvm-dtest-some -Dtest.name=org.apache.cassandra.distributed.test.SchemaTest

ant test-jvm-dtest-some -Dtest.name=org.apache.cassandra.distributed.test.SchemaTest -Dtest.methods=readRepair
----

[TIP]
.Hint
====
Unlike for JUnit tests, for JVM distributed tests you need to provide
fully qualified class name
====

Distributed tests can also be run using IDE (in fact, you can even debug
them).

==== Upgrade tests

JVM upgrade tests can be run precisely in the same way as any other JVM
distributed tests. However, running them requires some preparation -
for example, if a test verifies the upgrade from Cassandra 3.0 and
Cassandra 3.11 to the current version (say Cassandra 4.0), you need to
have prepared dtest uber JARs for all involved versions. To do this:

. Check out Cassandra 3.0 based branch you want to test the upgrade
from into some other directory

. Build dtest uber JAR with `ant dtest-jar` command

. Copy the created `build/dtest-3.0.x.jar` to the build
directory of your target Cassandra project

. Repeat the procedure for Cassandra 3.11

. Once you have dtest jars of all the involved versions for the upgrade
test, you can finally execute the test using your favorite method, say:

[source,plaintext]
----
ant test-jvm-dtest-some -Dtest.name=org.apache.cassandra.distributed.upgrade.MixedModeReadTest
----

[TIP]
.Hint
====
You may pre-generate dtest uber JARs for certain past Cassandra
releases, store is somewhere and reuse in you future work - no need to
rebuild them all the time.
====

=== Running multiple tests

It is possible to define a list of test classes to run with a single command. 
Define a text file, by default called `testlist.txt`, and put it into your project directory. 
Here is an example of that file:

[source,none]
----
org/apache/cassandra/db/ReadCommandTest.java
org/apache/cassandra/db/ReadCommandVerbHandlerTest.java
----

Essentially, you list the paths to the class files of the tests you want
to run. Then you call `ant testclasslist`, which uses the text file
to run the listed tests. Note that, by default, it applies to
the tests under the `test/unit` directory and takes the `testlist.txt`
file, but this behavior can be modified by providing additional
parameters:

[source,plaintext]
----
ant testclasslist -Dtest.classlistprefix=<category> -Dtest.classlistfile=<class list file>
----

For example, if you want to run the distributed tests this way, and say
our tests were listed in the `distributed-tests-set.txt` file (paths to
test classes relative to `test/distributed` directory), you can do that
by calling:

[source,plaintext]
----
ant testclasslist -Dtest.classlistprefix=distributed -Dtest.classlistfile=distributed-tests-set.txt
----

=== Running coverage analysis

Coverage reports from the executed JVM tests can be obtained in two ways
- through IDE - for example, IntelliJ supports running tests with
coverage analysis (another run button next to the one for running in debug mode).

The other way is to run Ant target `codecoverage`. Basically, it works
for all the ways mentioned above of running JVM tests - the only
difference is that instead of specifying the target directly, you pass it
as a property called `taskname`. For example - given the original test
command is:

[source,plaintext]
----
ant testsome -Dtest.name=org.apache.cassandra.utils.concurrent.AccumulatorTest
----

to run it with coverage analysis, do:

[source,plaintext]
----
ant codecoverage -Dtaskname=testsome -Dtest.name=org.apache.cassandra.utils.concurrent.AccumulatorTest
----

It applies to all the targets like `test`, `testsome`, `test-long`,
etc., even `testclasslist`. You can find the coverage report in
`build/jacoco` (`index.html` is the entry point for the HTML version,
but there are also XML and CSV reports).

Note that if you run various tests that way, the coverage information is
added to the previously collected runs. That is, you get the cumulative
coverage from all runs unless you clean up the project or at least clean
up the recorded coverage information by executing the command
`ant jacoco-cleanup`.

[#microbenchmarks]
=== Micro-benchmarks

To run micro-benchmarks, first build the uber jar for the JMH framework.
Use the following `ant` command:

[source,plaintext]
----
ant build-jmh
----

Then, you can run either all benchmarks (from the `test/microbench`
directory) or the tests matching the name specified by the
`benchmark.name` property when executing the `ant microbench` command.
Whether you run all benchmarks or just a selected one, only classes
under the `microbench` package are selected. The class selection pattern
is actually `.\*microbench.*${benchmark.name}`. For example,
in order to run `org.apache.cassandra.test.microbench.ChecksumBench`,
execute:

[source,plaintext]
----
ant microbench -Dbenchmark.name=ChecksumBench
----

The `ant microbench` command runs the benchmarks with default parameters
as defined in the `build.xml` file (see the `microbench` target
definition). If you want to run JMH with custom parameters,
consider using the `test/bin/jmh` script. In addition to allowing you to
customize JMH options, it also sets up the environment and JVM options
by running Cassandra init script (`conf/cassandra-env.sh`). Therefore,
it lets the environment for running the tests to be more similar to
the production environment. For example:

[source,plaintext]
----
test/bin/jmh -gc true org.apache.cassandra.test.microbench.CompactionBench.compactTest
----

You may also find it useful to run the command to list all the tests:
`test/bin/jmh -l` or `test/bin/jmh -lp` (also showing the default
parameters). The list of all options can be shown by running
`test/bin/jmh -h`

== Python tests

=== Docker

The Docker approach is recommended for running Python distributed tests.
The behavior will be more repeatable, matching the same environment as
the official testing on https://ci-cassandra.apache.org/[Cassandra CI].

==== Setup Docker

If you are on Linux, you need to install Docker using the system package
manager.

If you are on MacOS, you can use either
https://www.docker.com/products/docker-desktop[Docker Desktop] or some
https://runnable.com/docker/install-docker-on-macos[other approach].

==== Pull the Docker image

The Docker image used on the official Cassandra CI can be found in
https://github.com/apache/cassandra-builds[this] repository.
You can use either
https://github.com/apache/cassandra-builds/blob/trunk/docker/testing/ubuntu2004_j11.docker[docker/testing/ubuntu2004_j11.docker]
or
https://github.com/apache/cassandra-builds/blob/trunk/docker/testing/ubuntu2004_j11_w_dependencies.docker[docker/testing/ubuntu2004_j11_w_dependencies.docker]
The second choice has prefetched dependencies for building each main
Cassandra branch. Those images can be either built
locally (as per instructions in the GitHub repo) or pulled from the
Docker Hub - see
https://hub.docker.com/search?q=apache%2Fcassandra-testing&type=image[here].

First, pull the image from Docker Hub (it will either fetch or
update the image you previously fetched):

[source,plaintext]
----
docker pull apache/cassandra-testing-ubuntu2004-java11-w-dependencies
----

==== Start the container

[source,plaintext]
----
docker run -di -m 8G --cpus 4 \
--mount type=bind,source=/path/to/cassandra/project,target=/home/cassandra/cassandra \
--mount type=bind,source=/path/to/cassandra-dtest,target=/home/cassandra/cassandra-dtest \
--name test \
apache/cassandra-testing-ubuntu2004-java11-w-dependencies \
dumb-init bash
----

[TIP]
.Hint
====
Many distributed tests are not that demanding in terms of resources
- 4G / 2 cores should be enough to start one node. However, some tests
really run multiple nodes, and some of them are automatically skipped
if the machine has less than 32G (there is a way to force running them
though). Usually 8G / 4 cores is a convenient choice which is enough
for most of the tests.
====

To log into the container, use the following `docker exec` command:

[source,plaintext]
----
docker exec -it `docker container ls -f name=test -q` bash
----

[#setup_python_env]
==== Setup Python environment

The tests are implemented in Python, so a Python virtual environment
(see https://docs.python.org/3/tutorial/venv.html[here] for details)
with all the required dependencies is good to be set up. If you are
familiar with the Python ecosystem, you know what it is all about.
Otherwise, follow the instructions; it should be enough to run the
tests.

For Python distributed tests do:

[source,plaintext]
----
cd /home/cassandra/cassandra-dtest
virtualenv --python=python3 --clear --always-copy ../dtest-venv
source ../dtest-venv/bin/activate
CASS_DRIVER_NO_CYTHON=1 pip install -r requirements.txt
----

For CQLSH tests, replace some paths:

[source,plaintext]
----
cd /home/cassandra/cassandra/pylib
virtualenv --python=python3 --clear --always-copy ../../cqlsh-venv
source ../../cqlsh-venv/bin/activate
CASS_DRIVER_NO_CYTHON=1 pip install -r requirements.txt
----

[TIP]
.Hint
====
You may wonder why this weird environment variable `CASS_DRIVER_NO_CYTHON=1` was added - it is not required at all. Still, it allows avoiding the compilation of Cassandra driver with Cython, which is not needed unless you want to test that Cython compiled driver. In the end, it speeds up the installation of the requirements significantly from the order of minutes to the order of seconds.
====

The above commands are also helpful for importing those test projects
into your IDE. In that case, you need to run them on your host
system rather than in Docker container. For example, when you open the
project in IntelliJ, the Python plugin may ask you to select the runtime
environment. In this case, choose the existing _virtualenv_
based environment and point to `bin/python` under the created
`dtest-venv` directory (or `cqlsh-venv`, or whichever name you have
chosen).

Whether you want to play with Python distributed tests or CQLSH tests,
you need to select the right virtual environment. Remember to switch to
the one you want:

[source,plaintext]
----
deactivate
source /home/cassandra/dtest-venv/bin/activate
----

or

[source,plaintext]
----
deactivate
source /home/cassandra/cqlsh-venv/bin/activate
----

[#cqlsh_tests]
=== CQLSH tests

CQLSH tests are located in the `pylib/cqlshlib/test` directory. 
There is a helper script that runs the tests for you. In
particular, it builds the Cassandra project, creates a virtual
environment, runs the CCM cluster, executes the tests, and eventually
removes the cluster. You find the script in the `pylib` directory. The
only argument it requires is the Cassandra project directory:

[source,plaintext]
----
cassandra@b69a382da7cd:~/cassandra/pylib$ ./cassandra-cqlsh-tests.sh /home/cassandra/cassandra
----

Refer to the https://github.com/apache/cassandra/blob/trunk/pylib/README.asc[README] for further information.

==== Running selected tests

You may run all test tests from the selected file by passing that
file as an argument:

[source,plaintext]
----
~/cassandra/pylib/cqlshlib$ pytest test/test_constants.py
----

To run a specific test case, you need to specify the module, class name,
and the test name, for example:

[source,plaintext]
----
~/cassandra/pylib/cqlshlib$ pytest cqlshlib.test.test_cqlsh_output:TestCqlshOutput.test_boolean_output
----

[#python_dtests]
=== Python distributed tests

One way of doing integration or system testing at larger scale is
using https://github.com/apache/cassandra-dtest[dtest] (Cassandra distributed test).
These dtests automatically setup Cassandra clusters with certain configurations and simulate use cases you want to test.

The best way to learn how to write dtests is probably by reading the
introduction "http://www.datastax.com/dev/blog/how-to-write-a-dtest[How
to Write a Dtest]".
Looking at existing, recently updated tests in the project is another good activity.
New tests must follow certain
https://github.com/apache/cassandra-dtest/blob/master/CONTRIBUTING.md[style
conventions] that are checked before contributions are accepted.
In contrast to Cassandra, dtest issues and pull requests are managed on
github, therefore you should make sure to link any created dtests in your
Cassandra ticket and also refer to the ticket number in your dtest PR.

Creating a good dtest can be tough, but it should not prevent you from
submitting patches!
Please ask in the corresponding JIRA ticket how to write a good dtest for the patch.
In most cases a reviewer or committer will able to support you, and in some cases they may offer to write a dtest for you.

==== Run the tests - quick examples

Note that you need to set up and activate the virtualenv for DTests
(see <<setup_python_env>> section for details). Tests are implemented
with the PyTest framework, so you use the pytest command to run them.
Let’s run some tests:

[source,plaintext]
----
pytest --cassandra-dir=/home/cassandra/cassandra schema_metadata_test.py::TestSchemaMetadata::test_clustering_order
----

That command runs the `test_clustering_order` test case from
`TestSchemaMetadata` class, located in the `schema_metadata_test.py`
file. You may also provide the file and class to run all test cases from
that class:

[source,plaintext]
----
pytest --cassandra-dir=/home/cassandra/cassandra schema_metadata_test.py::TestSchemaMetadata
----

or just the file name to run all test cases from all classes defined in that file.

[source,plaintext]
----
pytest --cassandra-dir=/home/cassandra/cassandra schema_metadata_test.py
----

You may also specify more individual targets:

[source,plaintext]
----
pytest --cassandra-dir=/home/cassandra/cassandra schema_metadata_test.py::TestSchemaMetadata::test_basic_table_datatype  schema_metadata_test.py::TestSchemaMetadata::test_udf
----

If you run pytest without specifying any test, it considers running all
the tests it can find. More on the test selection
https://docs.pytest.org/en/6.2.x/usage.html#specifying-tests-selecting-tests[here]
You probably noticed that `--cassandra-dir=/home/cassandra/cassandra`
is constantly added to the command line. It is
one of the `cassandra-dtest` custom arguments - the mandatory one -
unless it is defined, you cannot run any Cassandra dtest.

==== Setting up PyTest

All the possible options can be listed by invoking pytest `--help`. You
see tons of possible parameters - some of them are native PyTest
options, and some come from Cassandra DTest. When you look carefully at
the help note, you notice that some commonly used options, usually fixed
for all the invocations, can be put into the `pytest.ini` file. In
particular, it is quite practical to define the following:

[source, none]
----
cassandra_dir = /home/cassandra/cassandra
log_cli = True
log_cli_level = DEBUG
----

so that you do not have to provide `--cassandra-dir` param each time you
run a test. The other two options set up console logging - remove them
if you want logs stored only in log files.

==== Running tests with specific configuration

There are a couple of options to enforce exact test configuration (their
names are quite self-explanatory):

* `--use-vnodes`
* `--num-token=xxx` - enables the support of virtual nodes with a certain
number of tokens
* `--use-off-heap-memtables` - use off-heap memtables instead of the
default heap-based
* `--data-dir-count-per-instance=xxx - the number of data directories
configured per each instance

Note that the list can grow in the future as new predefined
configurations can be added to dtests. It is also possible to pass extra
Java properties to each Cassandra node started by the tests - define
those options in the `JVM_EXTRA_OPTS` environment variable before
running the test.

==== Listing the tests

You can do a dry run, so that the tests are only listed and not
invoked. To do that, add `--collect-only` to the pytest command.
That additional `-q` option will print the  results in the same
format as you would pass the test name to the pytest command:

[source,plaintext]
----
pytest --collect-only -q
----

lists all the tests pytest would run if no particular test is specified.
Similarly, to list test cases in some class, do:

[source,plaintext]
----
$ pytest --collect-only -q schema_metadata_test.py::TestSchemaMetadata
schema_metadata_test.py::TestSchemaMetadata::test_creating_and_dropping_keyspace
schema_metadata_test.py::TestSchemaMetadata::test_creating_and_dropping_table
schema_metadata_test.py::TestSchemaMetadata::test_creating_and_dropping_table_with_2ary_indexes
schema_metadata_test.py::TestSchemaMetadata::test_creating_and_dropping_user_types
schema_metadata_test.py::TestSchemaMetadata::test_creating_and_dropping_udf
schema_metadata_test.py::TestSchemaMetadata::test_creating_and_dropping_uda
schema_metadata_test.py::TestSchemaMetadata::test_basic_table_datatype
schema_metadata_test.py::TestSchemaMetadata::test_collection_table_datatype
schema_metadata_test.py::TestSchemaMetadata::test_clustering_order
schema_metadata_test.py::TestSchemaMetadata::test_compact_storage
schema_metadata_test.py::TestSchemaMetadata::test_compact_storage_composite
schema_metadata_test.py::TestSchemaMetadata::test_nondefault_table_settings
schema_metadata_test.py::TestSchemaMetadata::test_indexes
schema_metadata_test.py::TestSchemaMetadata::test_durable_writes
schema_metadata_test.py::TestSchemaMetadata::test_static_column
schema_metadata_test.py::TestSchemaMetadata::test_udt_table
schema_metadata_test.py::TestSchemaMetadata::test_udf
schema_metadata_test.py::TestSchemaMetadata::test_uda
----

You can copy/paste the selected test case to the pytest command to
run it.

==== Filtering tests

===== Based on configuration

Most tests run with any configuration, but a subset of tests (test
cases) only run if a specific configuration is used. In particular,
there are tests annotated with:

* `@pytest.mark.vnodes` - the test is only invoked when the support of
virtual nodes is enabled
* `@pytest.mark.no_vnodes` - the test is only invoked when the support
of virtual nodes is disabled
* `@pytest.mark.no_offheap_memtables` - the test is only invoked if
off-heap memtables are not used

Note that enabling or disabling _vnodes_ is obviously mutually
exclusive. If a test is marked to run only with _vnodes_, it does not
run when _vnodes_ is disabled; similarly, when a test is marked to run
only without _vnodes_, it does not run when _vnodes_ is enabled -
therefore, there are always some tests which would not run with a single
configuration.

===== Based on resource usage

There are also tests marked with:

`@pytest.mark.resource_intensive`

which means that the test requires more resources than a regular test
because it usually starts a cluster of several nodes. The meaning of
resource-intensive is hardcoded to 32GB of available memory, and unless
your machine or docker container has at least that amount of RAM, such
test is skipped. There are a couple of arguments that allow for some
control of that automatic exclusion:

* `--force-resource-intensive-tests` - forces the execution of tests
marked as `resource_intensive`, regardless of whether there is enough
memory available or not
* `--only-resource-intensive-tests` - only run tests marked as
`resource_intensive` - it makes all the tests without
`resource_intensive` annotation to be filtered out; technically, it is
equivalent to passing native PyTest argument: `-m resource_intensive`
* `--skip-resource-intensive-tests` - skip all tests marked as
`resource_intensive` - it is the opposite argument to the previous one,
and it is equivalent to the PyTest native argument: `-m 'not resource_intensive'`

===== Based on the test type

Upgrade tests are marked with:

`@pytest.mark.upgrade_test`

Those tests are not invoked by default at all (just like running
PyTest with `-m 'not upgrade_test'`), and you have to add some extra
options to run them:
* `--execute-upgrade-tests` - enables execution of upgrade tests along
with other tests - when this option is added, the upgrade tests are not
filtered out
* `--execute-upgrade-tests-only` - execute only upgrade tests and filter
out all other tests which do not have `@pytest.mark.upgrade_test`
annotation (just like running PyTest with `-m 'upgrade_test'`)

===== Filtering examples

It does not matter whether you want to invoke individual tests or all
tests or whether you only want to list them; the above filtering rules
apply. So by using `--collect-only` option, you can learn which tests
would be invoked.

To list all the applicable tests for the current configuration, use the
following command:

[source,plaintext]
----
pytest --collect-only -q --execute-upgrade-tests --force-resource-intensive-tests
----

List tests specific to vnodes (which would only run if vnodes are enabled):

[source,plaintext]
----
pytest --collect-only -q --execute-upgrade-tests --force-resource-intensive-tests --use-vnodes -m vnodes
----

List tests that are not resource-intensive

[source,plaintext]
----
pytest --collect-only -q --execute-upgrade-tests --skip-resource-intensive-tests
----

==== Upgrade tests

Upgrade tests always involve more than one product version. There are
two kinds of upgrade tests regarding the product versions they span -
let’s call them fixed and generated.

In case of fixed tests, the origin and target versions are hardcoded.
They look pretty usual, for example:

[source,plaintext]
----
pytest --collect-only -q --execute-upgrade-tests --execute-upgrade-tests-only upgrade_tests/upgrade_supercolumns_test.py
----

prints:

[source,plaintext]
----
upgrade_tests/upgrade_supercolumns_test.py::TestSCUpgrade::test_upgrade_super_columns_through_all_versions
upgrade_tests/upgrade_supercolumns_test.py::TestSCUpgrade::test_upgrade_super_columns_through_limited_versions
----

When you look into the code, you will see the fixed upgrade path:

[source, python]
----
def test_upgrade_super_columns_through_all_versions(self):
    self._upgrade_super_columns_through_versions_test(upgrade_path=[indev_2_2_x, indev_3_0_x, indev_3_11_x, indev_trunk])
----

The generated upgrade tests are listed several times - the first
occurrence of the test case is a generic test definition, and then
it is repeated many times in generated test classes. For example:

[source,plaintext]
----
pytest --cassandra-dir=/home/cassandra/cassandra --collect-only -q --execute-upgrade-tests --execute-upgrade-tests-only upgrade_tests/cql_tests.py -k test_set
----

prints:

[source,plaintext]
----
upgrade_tests/cql_tests.py::cls::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_current_2_2_x_To_indev_2_2_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_current_3_0_x_To_indev_3_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_current_3_11_x_To_indev_3_11_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_current_4_0_x_To_indev_4_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_indev_2_2_x_To_indev_3_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_indev_2_2_x_To_indev_3_11_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_indev_3_0_x_To_indev_3_11_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_indev_3_0_x_To_indev_4_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_indev_3_11_x_To_indev_4_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_indev_4_0_x_To_indev_trunk::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_current_2_2_x_To_indev_2_2_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_current_3_0_x_To_indev_3_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_current_3_11_x_To_indev_3_11_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_current_4_0_x_To_indev_4_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_indev_2_2_x_To_indev_3_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_indev_2_2_x_To_indev_3_11_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_indev_3_0_x_To_indev_3_11_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_indev_3_0_x_To_indev_4_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_indev_3_11_x_To_indev_4_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_indev_4_0_x_To_indev_trunk::test_set
----

In this example, the test case name is just `test_set`, and the class
name is `TestCQL` - the suffix of the class name is automatically
generated from the provided specification. The first component is the
cluster specification - there are two variants: `Nodes2RF1` and `Nodes3RF3`
- they denote that the upgrade is tested on 2 nodes cluster with a
keyspace using replication factor = 1. Analogously the second variant
uses 3 nodes cluster with RF = 3.

Then, there is the upgrade specification - for example,
`Upgrade_indev_3_11_x_To_indev_4_0_x` - which means that this test
upgrades from the development version of Cassandra 3.11 to the
development version of Cassandra 4.0 - the meaning of `indev/current`
and where they are defined is explained later.

When you look into the implementation, you notice that such upgrade test
classes inherit from `UpgradeTester` class, and they have the
specifications defined at the end of the file. In this particular case,
it is something like:

[source, python]
----
topology_specs = [
    {'NODES': 3,
     'RF': 3,
     'CL': ConsistencyLevel.ALL},
    {'NODES': 2,
     'RF': 1},
]
specs = [dict(s, UPGRADE_PATH=p, __test__=True)
for s, p in itertools.product(topology_specs, build_upgrade_pairs())]
----

As you can see, there is a list of the cluster specifications and
the cross product is calculated with upgrade paths returned by the
`build_upgrade_pairs()` function. That list of specifications is used to
dynamically generate upgrade tests.

Suppose you need to test something specifically for your scenario. In
that case, you can add more cluster specifications, like a test with 1
node or a test with 5 nodes with some different replication factor or
consistency level. The `build_upgrade_pairs()` returns the list of
upgrade paths (actually just the origin and target version). That list
is generated according to the upgrade manifest.

===== Upgrade manifest

The upgrade manifest is a file where all the upgrade paths are defined.
It is a regular Python file located at
`upgrade_tests/upgrade_manifest.py`.
As you noticed, Cassandra origin and target version descriptions
mentioned in the upgrade test consist of `indev` or `current` prefix
followed by version string. The definitions of each such version
description can be found in the manifest, for example:

[source, python]
----
indev_3_11_x = VersionMeta(name='indev_3_11_x', family=CASSANDRA_3_11, variant='indev', version='github:apache/cassandra-3.11', min_proto_v=3, max_proto_v=4, java_versions=(8,))

current_3_11_x = VersionMeta(name='current_3_11_x', family=CASSANDRA_3_11, variant='current', version='3.11.10', min_proto_v=3, max_proto_v=4, java_versions=(8,))
----

There are a couple of different properties which describe those two
versions:

* `name` - is a name as you can see in the names of the generated
test classes
* `family` - families is an enumeration defined in the beginning of
the upgrade manifest - say family `CASSANDRA_3_11` is just a string
`"3.11"`. Some major features were introduced or removed with new
version families, and therefore some checks can be done or some features
can be enabled/disabled according to that, for example:

[source, python]
----
if self.cluster.version() < CASSANDRA_4_0:
    node1.nodetool("enablethrift")
----

But it is also used to determine whether our checked-out version matches
the target version in the upgrade pair (more on that later)

* `variant` and `version` - there are `indev` or `current` variants:
** `indev` variant means that the development version of Cassandra
will be used. That is, that version is checked out from the Git
repository and built before running the upgrade (CCM does it). In this
case, the version string is specified as `github:apache/cassandra-3.11`,
which means that it will checkout the `cassandra-3.11` branch from the
GitHub repository whose alias is `apache`. Aliases are defined in CCM
configuration file, usually located at `~/.ccm/config` - in this
particular case, it could be something like:

[source, none]
----
[aliases]
apache:git@github.com:apache/cassandra.git
----

** `current` variant means that a released version of Cassandra will
be used. It means that Cassandra distribution denoted by the specified
version (3.11.10 in this case) is downloaded from the Apache
repository/mirror - again, the repository can be defined in CCM
configuration file, under repositories section, something like:

[source,none]
----
[repositories]
cassandra=https://archive.apache.org/dist/cassandra
----

* `min_proto_v`, `max_proto_v` - the range of usable Cassandra driver
protocol versions
* `java_versions` - supported Java versions

The possible upgrade paths are defined later in the upgrade manifest -
when you scroll the file, you will find the `MANIFEST` map which may
look similar to:

[source, python]
----
MANIFEST = {
current_2_1_x: [indev_2_2_x, indev_3_0_x, indev_3_11_x],
current_2_2_x: [indev_2_2_x, indev_3_0_x, indev_3_11_x],
current_3_0_x: [indev_3_0_x, indev_3_11_x, indev_4_0_x],
current_3_11_x: [indev_3_11_x, indev_4_0_x],
current_4_0_x: [indev_4_0_x, indev_trunk],

   indev_2_2_x: [indev_3_0_x, indev_3_11_x],
   indev_3_0_x: [indev_3_11_x, indev_4_0_x],
   indev_3_11_x: [indev_4_0_x],
   indev_4_0_x: [indev_trunk]
}
----

It is a simple map where for the origin version (as a key), there is
a list of possible target versions (as a value). Say:

[source, python]
----
current_4_0_x: [indev_4_0_x, indev_trunk]
----

means that upgrades from `current_4_0_x` to
`indev_4_0_x` and from `current_4_0_x` to `indev_trunk` will be considered.
You may make changes to that upgrade scenario in your development branch
according to your needs.
There is a command-line option that allows filtering across upgrade
scenarios: `--upgrade-version-selection=xxx`. The possible values for
that options are as follows:

* `indev` - which is the default, only selects those upgrade scenarios
where the target version is in `indev` variant
* `both` - selects upgrade paths where either both origin and target
versions are in the same variant or have the same version family
* `releases` - selects upgrade paths between versions in current variant
or from the `current` to `indev` variant if both have the same version
family
* `all` - no filtering at all - all variants are tested

==== Running upgrades with local distribution

The upgrade test can use your local Cassandra distribution, the one
specified by the `cassandra_dir` property, as the target version if the
following preconditions are satisfied:

* the target version is in the `indev` variant,
* the version family set in the version description matches the version
family of your local distribution

For example, your local distribution is branched off from the
`cassandra-4.0` branch, likely matching `indev_4_0_x`. It means that the
upgrade path with target version `indev_4_0_x` uses your local
distribution.
There is a handy command line option which will filter out all the
upgrade tests which do not match the local distribution:
`--upgrade-target-version-only`. Given you are on `cassandra-4.0` branch,
when applied to the previous example, it will be something similar to:

[source,plaintext]
----
pytest --cassandra-dir=/home/cassandra/cassandra --collect-only -q --execute-upgrade-tests --execute-upgrade-tests-only upgrade_tests/cql_tests.py -k test_set --upgrade-target-version-only
----

prints:

[source,plaintext]
----
upgrade_tests/cql_tests.py::cls::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_current_4_0_x_To_indev_4_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_indev_3_0_x_To_indev_4_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes3RF3_Upgrade_indev_3_11_x_To_indev_4_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_current_4_0_x_To_indev_4_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_indev_3_0_x_To_indev_4_0_x::test_set
upgrade_tests/cql_tests.py::TestCQLNodes2RF1_Upgrade_indev_3_11_x_To_indev_4_0_x::test_set
----

You can see that the upgrade tests were limited to the ones whose target
version is `indev` and family matches 4.0.

==== Logging

A couple of common PyTest arguments control what is logged to the file
and the console from the Python test code. Those arguments which start
from `--log-xxx` are pretty well described in the help message
(`pytest --help`) and in PyTest documentation, so it will not be discussed
further. However, most of the tests start with the cluster of
Cassandra nodes, and each node generates its own logging information and
has its own data directories.

By default the logs from the nodes are copied to the unique directory
created under logs subdirectory under root of dtest project. For example:

[source,plaintext]
----
(venv) cassandra@b69a382da7cd:~/cassandra-dtest$ ls logs/ -1
1627455923457_test_set
1627456019264_test_set
1627456474949_test_set
1627456527540_test_list
last
----

The `last` item is a symbolic link to the directory containing the logs
from the last executed test. Each such directory includes logs from each
started node - system, debug, GC as well as standard streams registered
upon each time the node was started:

[source,plaintext]
----
(venv) cassandra@b69a382da7cd:~/cassandra-dtest$ ls logs/last -1
node1.log
node1_debug.log
node1_gc.log
node1_startup-1627456480.3398306-stderr.log
node1_startup-1627456480.3398306-stdout.log
node1_startup-1627456507.2186499-stderr.log
node1_startup-1627456507.2186499-stdout.log
node2.log
node2_debug.log
node2_gc.log
node2_startup-1627456481.10463-stderr.log
node2_startup-1627456481.10463-stdout.log
----

Those log files are not collected if `--delete-logs` command-line option
is added to PyTest. The nodes also produce data files which may be
sometimes useful to examine to resolve some failures. Those files are
usually deleted when the test is completed, but there are some options
to control that behavior:

* `--keep-test-dir` - keep the whole CCM directory with data files and
logs when the test completes
* `--keep-failed-test-dir` – only keep that directory when the test has
failed

Now, how to find where is that directory for the certain test - you need
to grab that information from the test logs - for example, you may add
`-s` option to the command line and then look for `"dtest_setup INFO"`
messages. For example:

[source,plain]
----
05:56:06,383 dtest_setup INFO cluster ccm directory: /tmp/dtest-0onwvgkr
----

says that the cluster work directory is `/tmp/dtest-0onwvgkr`, and all
node directories can be found under the `test` subdirectory:

[source,plaintext]
----
(venv) cassandra@b69a382da7cd:~/cassandra-dtest$ ls /tmp/dtest-0onwvgkr/test -1
cluster.conf
node1
node2
----

== Performance Testing

Performance tests for Cassandra are a special breed of tests that are
not part of the usual patch contribution process. In fact, many people
contribute a lot of patches to Cassandra without ever running performance
tests. However, they are important when working on performance
improvements; such improvements must be measurable.

Several tools exist for running performance tests. Here are a few to investigate:

* Described above <<microbenchmarks>>
* `cassandra-stress`: built-in Cassandra stress tool
* https://github.com/thelastpickle/tlp-stress[tlp-stress]
* https://github.com/nosqlbench/nosqlbench[NoSQLBench]