spring-test-data-geode/README.adoc

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[[about]]
== Spring Test Framework for Apache Geode & VMware Tanzu GemFire

The STDG project is a _Spring Data_ module, building on the core _Spring Framework's_ `TestContext`, used to write
_Unit_ and _Integration Tests_ when building _Spring Data_ for https://geode.apache.org/[Apache Geode]
& https://pivotal.io/pivotal-gemfire[VMware GemFire] (SDG) applications.

This project was born from https://spring.io/projects/spring-data-gemfire[_Spring Data for VMware GemFire's_]
(https://github.com/spring-projects/spring-data-gemfire[@GitHub])
https://github.com/spring-projects/spring-data-gemfire/tree/2.1.19.RELEASE/src/test/java/org/springframework/data/gemfire/test[test framework].
This _test framework_ is used in SDG's test suite to test the proper function and behavior of Apache Geode
& VMware GemFire in a _Spring_ context.

For several years now, users have asked for a better way to test their Apache Geode & VMware GemFire based,
_Spring_ applications reliably and easily, particularly when writing _Unit_ and _Integrations_ tests.

Additionally, STDG was created to consolidate the testing efforts, lessons learned, and knowledge and experience of
effectively testing all Spring for Apache Geode/VMware GemFire projects: _Spring Boot for Apache Geode & VMware GemFire_
(SBDG) and _Spring Session for Apache Geode & VMware GemFire_ (SSDG) in addition to
_Spring Data for Apache Geode & VMware GemFire_ (SDG).

Eventually, STDG will replace the SDG test classes so that tests and testing efforts are consistent across all Spring
projects for Apache Geode/VMware GemFire: SDG, SSDG and SBDG.

This (relatively) **new** project is still under development and will have documentation, examples and an extensive test
suite once completed.

In the meantime, you can review the
https://github.com/spring-projects/spring-boot-data-geode/tree/master/spring-geode-autoconfigure/src/test/java/org/springframework/geode/boot/autoconfigure[test suite for SBDG]
and the https://github.com/spring-projects/spring-session-data-geode/tree/master/spring-session-data-geode/src/test/java/org/springframework/session/data/gemfire[test suite for SSDG]
to get a sense of how this project is used and works.

[[code-of-conduct]]
== Code of Conduct

Please see our https://github.com/spring-projects/.github/blob/master/CODE_OF_CONDUCT.md[code of conduct]

[[report-security-vulnerability]]
== Reporting Security Vulnerabilities

Please see our https://github.com/spring-projects/spring-test-data-geode/security/policy[Security policy].

[[license]]
== License

_Spring Test for Apache Geode_ and _Spring Test for VMware GemFire_ is Open Source Software
released under the https://www.apache.org/licenses/LICENSE-2.0.html[Apache 2.0 license].


[[nutshell]]
== STDG in a Nutshell

Until proper documentation has been provided, this very short and simple tutorial will hopefully give you a better idea
of how this project is used.


[[unit-tests]]
=== Unit Testing with STDG

We all write tests, right?  TDD style?  ;-)

As we begin to write tests, we typically start with _Unit Tests_ since they are designed to test the subject
in isolation without actual collaborators and dependencies in order to gather feedback quickly,
i.e. "_Is my logic correct?_"

It common when writing _Unit Tests_ to *mock* the collaborators/dependencies since the test should assume that the
dependencies "_work as designed_".  During _Unit Testing_, it does not matter whether or not the dependencies actually
work as expected (that is the purpose of _Integration Tests_ or the _Unit Tests_ for the dependencies themselves), just
that they have a contract and our application components, the "_Subject Under Test_" (SUT), honors that contract and
uses the external dependencies correctly. Essentially we are asserting that the interactions between our application
components and external collaborators/dependencies are correct and the results lead to the desired outcome.

Well, it is, or should be, no different when you are using Apache Geode or VMware GemFire.

For instance, you might want to mock that your _Data Access Object_ (DAO) performs the proper interactions on
a GemFire/Geode Region, performing the right CRUD operations, making sure the right (OQL) Queries are executed
for the Use Case or business function and workflow being performed by the application.

In this case, we don't care whether the Region is real or not, or that an OQL Query is actually well formed and would
execute properly, performantly, returning the correct results.  We would "mock" the Regions' behavior in this case
to make sure that our DAO interactions with the Region are correct, that it handles the translation of Exceptions
or other Error conditions, that it transforms values to/from the backend data store (i.e. Region), and so on. That is
how you properly test the subject.

To support _Unit Testing_ with Apache Geode or VMware GemFire in a Spring context, STDG provides the
`@EnableGemFireMockObjects` annotation.  If you want to use GemFire/Geode Mock Objects, e.g. a "mock" Region rather
than a "live" Region, than you simply only need to annotate your test configuration with `@EnableGemFireMockObjects`.

For example:

.Unit Test with GemFire/Geode Mock Objects
[source,java]
----
@RunWith(SpringRunner.class)
@ContextConfiguration
class ExampleUnitTestClass {

  // test case methods here

  @EnableGemFireMockObjects
  @ClientCacheApplication
  @EnableEntityDefinedRegions(basePackageClasses=ExampleEntity.class,
      clientRegionShortcut = ClientRegionShortcut.LOCAL)
  static class TestConfiguration { }

}
----


In the example above, the `@EnableGemFireMockObjects` annotation creates "mocks" for the `ClientCache`, all the `Regions`
identified and created by the `@EnableEntityDefinedRegions(..)` annotation, along with all the other GemFire/Geode
object types. There are no "live" GemFire/Geode objects when "mocking" is enabled.

Here is 1
https://github.com/spring-projects/spring-test-data-geode/blob/master/spring-data-geode-test/src/test/java/org/springframework/data/gemfire/MockClientCacheApplicationIntegrationTests.java[example]
of a concrete _Unit Test_ in action, using STDG's `@EnableGemFireMockObjects` annotation.

It really is that simple!

TIP: Mocking GemFire/Geode objects outside a Spring context is possible, but beyond the scope of this simple tutorial
for the time being.

[[unit-tests-mock-object-cleanup]]
==== Mock Object Scope & Lifecycle Management

Currently, GemFire/Geode mock objects are cleaned up after an individual test class runs. Therefore, the mocked
GemFire/Geode objects persist for the entire lifecycle of a single test class, or test suite, and can be reused
across all the test cases of the test class.

The Spring `TestContext` framework emits certain "test" events during the test lifecycle as documented in
the `EventPublishingTestExecutionListener` class https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/test/context/event/EventPublishingTestExecutionListener.html[_Javadoc_].
The test events are actually contained in the https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/test/context/event/package-summary.html[`org.springframework.test.context.event`] package.

Currently, STDG defaults the cleanup of all mocked GemFire/Geode objects to the
https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/test/context/event/AfterTestClassEvent.html[`AfterTestClassEvent`] type.

By way of example, this would be equivalent to:

.Default STDG GemFire/Geode mock object cleanup
[source,java]
----
@RunWith(SpringRunner.class)
@ContextConfiguration
class ExampleTest {

	@ClientCacheApplication
    @EnableGemFireMockObject(destroyOnEvents = AfterTestClassEvent.class)
	static class TestConfiguration { }

}
----

You might want to cleanup all GemFire/Geode mock objects after each test case method in your test class using
the https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/test/context/event/AfterTestMethodEvent.html[`AfterTestMethodEvent`] class.

In this case, you can do:

.GemFire/Geode mock object cleanup after each test case
[source,java]
----
@RunWith(SpringRunner.class)
@ContextConfiguration
class ExampleTest {

	@ClientCacheApplication
    @EnableGemFireMockObject(destroyOnEvents = AfterTestMethodEvent.class)
	static class TestConfiguration { }

}
----

The `destroyOnEvents` attribute of the `@EnableGemFireMockObjects` annotation accepts more than one test event type,
thereby allowing to perform GemFire/Geode mock object cleanup at multiple points in the test lifecycle.

For example, maybe you need to cleanup all mocked GemFire/Geode objects before each test case executes and after each
test class completes:

.GemFire/Geode mock object cleanup before each test case executes and after each test class completes
[source,java]
----
@RunWith(SpringRunner.class)
@ContextConfiguration
class ExampleTest {

	@ClientCacheApplication
    @EnableGemFireMockObject(destroyOnEvents = { BeforeTestExecutionEvent.class, AfterTestClassEvent.class })
	static class TestConfiguration { }

}
----

You now have the granularity required to control the scope and lifecycle of the GemFire/Geode mocked objects in STDG.


[[unit-tests-mock-region-data]]
==== Mock Regions with Data

While implementing a fully capable GemFire/Geode Region would defeat the purpose of Mocking and Unit Testing in general,
it is desirable to sometimes perform basic Region data access operations, such as `get` and `put`, with small quantities
of data and emulate, or simulate the same effects.

As such, with STDG, it is currently possible to perform the following Region data access operations:

* `clear()`
* `containsKey(key)`
* `containsValue(value)`
* `containsValueForKey(value)`
* `forEach(:BiConsumer<K, V>)`
* `get(key)`
* `getAll()`
* `getEntry(key)`
* `getOrDefault(key, defaultValue)`
* `invalidate(key)`
* `isEmpty()`
* `keySet()`
* `localClear()`
* `localValidate()`
* `put(key, value)`
* `putAll(:Map<K, V>)`
* `remove(key)`
* `removeAll(:Collection<K>)`
* `size()`
* `values()`

NOTE: Some mock Map/Region data access operations are still being considered, such as: `putIfAbsent(key, value)`,
`remove(key, value)`, `replace(key, value)`, `replace(key, oldValue, newValue)` and `replaceAll(:BiFunction<K, V>)`.
Other mock Region data access operations will not be implemented at all (e.g. `keySetOnServer()` or `sizeOnServer()`,
etc) since they necessarily involve a more complex topology. Regardless, you can still mock any Map/Region operation
you like by following these <<unit-tests-mock-unsupported-region-ops,instructions>>.

WARNING: Some mock Map/Region data access operations are implemented in terms of other Map/Region operations
(e.g. `putAll(:Map<K, V))` is implemented in terms of `put(key, value)`) and are therefore compound actions
that are not atomic.  In other words, we did not make the atomic.

The "mock" Region will behave and function similarly to an actual GemFire/Geode Region involving these
data access operations.

By way of example, this means you can do things like the following in a Unit Test with a "mock" Region:

.Basic data access operations on a mocked Region
[source,java]
----
@RunWith(SpringRunner.class)
@ContextConfiguration
class MyGeodeMockRegionUnitTests {

  @Resource(name = "Example")
  private Region<?, ?>  mockRegion;

  @Test
  public void simpleGetAndPutRegionOpsWork() {

      mockRegion.put(1, "test");

      assertThat(mockRegion).containsKey(1);
      assertThat(mockRegion.get(1)).isEqualTo("test");
  }

  @ClientCacheApplication
  @EnableGemFireMockObjects
  static class TestConfiguration {

    @Bean("Example")
    ClienRegionFactoryBean mockRegion(GemFireCache gemfireCache) {

        ClientRegionFactoryBean mockRegion = new ClientRegionFactoryBean();

        mockRegion.setCache(gemfireCache);

        return mockRegion;
    }
  }
}
----

Of course, you can also perform similar Region data access operations using the _Spring Data Repository_ abstraction
instead. The benefit of _Spring Data's_ _Repository_ abstraction is that it shields your application from Apache Geode
and hides the fact that you are interfacing with an Region under-the-hood by using the proper _Data Access Object_ (DAO)
pattern.

For example, you can "mock" a Region and `put`/`get` data using a _Spring Data Repository_ for the Region
as demonstrated in the following code.

Given a `Customer` application domain object annotated with the `@Region` mapping annotation:

.Customer
[source,java]
----
@Region("Customers")
class Customer {

    @Id
    private Long id;

    // ...

}
----

Along with a SD _Repository_ for `Customers`:

.CustomerRepository
[source,java]
----
interface CustomerRepository extends CrudRepository<Customer, Long> {
	//...
}
----

Then you can write a test class like the following, still using a "mock" Region to `put` and `get` actual data:

.Spring Data _Repository_ on a mocked Region
[source,java]
----
@RunWith(SpringRunner.class)
@ContextConfiguration
class MySpringDataRepositoryUnitTests {

    @Autowired
    private CustomerRepository customerRepository;

    @Test
    public void simpleRepositoryCrudOpsWork() {

        Customer jonDoe = new Customer(1L, "Jon Doe");

        customerRepository.save(jonDoe);

        assertThat(customerRepository.existsById(jonDoe.getId())).isTrue();
        assertThat(customerRepository.findById(jonDoe.getId()).orElse(null)).isEqualTo(jonDoe);
    }

    @ClientCacheApplication
    @EnableEntityDefinedRegions(basePackageClasses = Customer.class)
    @EnableGemfireRepositories(basePackageClasses = CustomerRepository.class)
    static class TestConfiguration {  }

}
----

Even though you are using _Spring Data Repositories_ and the `@EnableEntityDefinedRegions` annotation (perhaps;
yes these components still work with Mocks and mock data), you can still autowire (inject) the Region and access
it directly in the same test class:

.Accessing the mock Region directly in the SD _Repository_ test
[source,java]
----
@RunWith(SpringRunner.class)
@ContextConfiguration
class MySpringDataRepositoryWithMockRegionUnitTests {

    @Autowired
    private CustomerRepository customerRepository;

    @Resource(name = "Customers")
    private Region<Long, Customer> customers;

    @Test
    public void simpleRepositoryCrudOpsWork() {
    	//...
    }

    @Test
    public void customerRegionOpsWorkToo() {

        Customer janeDoe = new Customer(2L, "Jane Doe");

        customers.put(janeDoe.getId(), janeDoe);

        assertThat(customers).containsKey(janeDoe.getId());
        assertThat(customers.get(janeDoe.getId())).isEqualTo(janeDoe);
        assertThat(customerRepository.findById(janeDoe.getId()).orElse(null)).isEqualTo(janeDoe);
    }
}
----

While you are allowed to inject a Region directly into your test class, it is better to use SDG's `GemfireTemplate`,
which wraps and decorates a Region's data access operations.  `GemfireTemplate` provides a lower-level API, closer
to the Region API, than _Spring Data Repositories_ allowing you to perform and exercise more control over advanced
functions, while still shielding you from the Region API.

The test class above could be rewritten as:

.Accessing the mock Region using the SDG `GemfireTemplate` in the SD _Repository_ test
[source,java]
----
@RunWith(SpringRunner.class)
@ContextConfiguration
class MySpringDataRepositoryWithGemfireTemplateUnitTests {

    @Autowired
    private CustomerRepository customerRepository;

    @Autowired
    @Qualifier("customersTemplate")
    private GemfireTemplate customersTemplate;

    @Test
    public void simpleRepositoryCrudOpsWork() {
    	//...
    }

    @Test
    public void customerTemplateOpsWorkToo() {

        Customer janeDoe = new Customer(2L, "Jane Doe");

        customersTemplate.put(janeDoe.getId(), janeDoe);

        assertThat(customersTemplate).containsKey(janeDoe.getId());
        assertThat(customersTemplate.get(janeDoe.getId())).isEqualTo(janeDoe);
        assertThat(customerRepository.findById(janeDoe.getId()).orElse(null)).isEqualTo(janeDoe);
    }
}
----

For clarification, obviously many of the Region functions and behaviors are not implemented, like persistence
and overflow to disk, distribution, replication, eviction, expiration, querying, etc.  If you find you need to test
your application with these behaviors and functions, then your test would clearly be better suited as an actual
Integration Test.

[[unit-tests-mock-region-callbacks]]
==== Mock Region Callbacks

A relatively *new* feature in STDG is the ability to register and invoke cache (Region) callbacks, such as
`CacheListeners`, or a `CacheLoader` or a `CacheWriter`.

Cache callbacks like `CacheListeners` or `CacheLoader/Writers` are user-defined, application objects that can be
registered with a Region to listen for events, load data on cache misses, or write the Region's data to a backend,
external data source.

It is sometimes useful when testing to partially mock some dependencies (a.k.a. collaborators; e.g. Regions)
while using live objects for others (e.g. cache callbacks like a `CacheListener`).

The reason behind this testing strategy is that some objects are mostly infrastructure related (e.g. a Region),
and not the primary focus of the test, while other objects are still very much tied to the application's function
and behavior (e.g. a `CacheListener` or a `CacheLoader`), i.e. they are part of the application's workflow.

As such, STDG not only allows you to register `CacheListeners` and `CacheLoaders/Writers` (you could do so before
as well), but will now additionally invoke the Listeners, Loader and Writer at the appropriate point in the Region
operation's process flow.

For example, a registered `CacheWriter` is invoked before the object (value) is put into the Region using the
`Region.put(key, value)` operation.  This is exactly what GemFire/Geode does in order to ensure consistency with
the backend, external data source.  If the `CacheWriter` throws an exception during 1 of it's event handler callbacks
(e.g. `beforeCreate(:EntryEvent<K, V>)` then it will prevent the object from being inserted into the Region.
The same behavior is true for a STDG mock Region.

By way of example, let's demonstrate with a `CacheLoader`:

.Application `CacheLoader` on mock Region
[source,java]
----
@RunWith(SpringRunner.class)
@ContextConfiguration
class MyMockRegionWithCacheLoaderUnitTests {

  @Resource(name = "Example")
  private Region example;

  @Test
  public void cacheLoaderWorks() {

    assertThat(example.get("one")).isEqualTo(1);
    assertThat(example.get("two")).isEqualTo(2);
    // ...

  }

  @ClientCacheApplication
  @EnableGemFireMockObjects
  static class TestConfiguration {

    @Bean
    ClienRegionFactoryBean exampleRegion(GemFireCache gemfireCache) {

      ClientRegionFactoryBean exampleRegion = new ClientRegionFactoryBean();

      exampleRegion.setCache(gemfireCache);
      exampleRegion.setCacheLoader(counterCacheLoader());

      return exampleRegion;
    }
  }

  @Bean
  CacheLoader<Object, Object> counterCacheLoader() {

    AtomicInteger counter = new AtomicInteger(0);

    return new CacheLoader<>() {

      @Override
      public Object load(LoaderHelper<Object, Object> helper) {
        return counter.incrementAndGet();
      }
    };
  }
}
----

As seen in the test above, performing a `Region.get(key)` for keys "one" and "two" on an initially empty Region
will result in cache misses, which will then invoke the registered, application "counter" `CacheLoader` to supply
the value for the requested keys.

You can register a `CacheWriter` along with 1 or more `CacheListeners` and they will be invoked, too.

[[unit-tests-mock-unsupported-region-ops]]
==== Mocking Unsupported Region Operations

As stated in the <<unit-tests-mock-region-data>> section above, only the following Region data access operations are
supported by STDG out-of-the-box (OOTB):

* `clear()`
* `containsKey(key)`
* `containsValue(value)`
* `containsValueForKey(value)`
* `forEach(:BiConsumer<K, V>)`
* `get(key)`
* `getAll()`
* `getEntry(key)`
* `getOrDefault(key, defaultValue)`
* `invalidate(key)`
* `isEmpty()`
* `keySet()`
* `localClear()`
* `localValidate()`
* `put(key, value)`
* `putAll(:Map<K, V>)`
* `remove(key)`
* `removeAll(:Collection<K>)`
* `size()`
* `values()`

How then do you mock other Region operations (e.g. `putIfAbsent(key, value)`) provided by the Region API that is not
supported by STDG OOTB?

Fortunately, you can rely on the fact that the Region object returned when mocking with `@EnableGemFireMockObjects`
inside your _Unit Tests_ is a "_mock_" object, specifically mocked by _Mockito_. Therefore, you are able to mock
any other Region data access operations that might be required by your application given a reference to the "mock"
Region object.

For example, suppose you also want to mock the `putIfAbsent(key, value)` _Map_ operation on Region, then you can do:

.Mocking Region.putIfAbsent(key, value)
[source,java]
----
@RunWith(SpringRunner.class)
@ContextConfiguration
class ExampleUnitTest {

	@Autowired
    @Qualifer("exampleTemplate")
	GemfireTemplate exampleTemplate;

	@Resource(name = "Example")
	Region<?, ?> example;

	@Before
	public void setup() {

		doAnswer(invocation -> {

			Object key = invocation.getArgugment(0);
			Object value = invocation.getArgument(1);
			Object existingValue;

			synchronized (this.example) {

				existingValue = this.example.get(key);

				if (existingValue == null) {
					this.example.put(key, value);
				}
			}

			return existingValue;

		}).when(this.example).putIfAbsent(any(), any());
	}

	@Test
	public void putIfAbsentWorks() {

		assertThat(this.exampleTemplate.putIfAbsent(1, "test")).isNull();
		assertThat(this.exampleTemplate.putIfAbsent(1, "mock")).isEqualTo("test");
		assertThat(this.exampleTemplate.get(1)).isEqualTo("test");
	}

	@ClientCacheApplication
    @EnableGemFireMockObjects
	static class TestConfiguration {

        @Bean("Example")
        ClienRegionFactoryBean mockRegion(GemFireCache gemfireCache) {

            ClientRegionFactoryBean mockRegion = new ClientRegionFactoryBean();

            mockRegion.setCache(gemfireCache);

            return mockRegion;
        }

        @Bean
        GemfireTemplate exampleTemplate(GemFireCache gemfireCache) {
        	return new GemfireTemplate(gemifreCache.getRegion("/Example"));
        }
	}
}
----

While the `putIfAbsent(key, value)` operation above was mocked (implemented) in terms of the existing, mocked `get(key)`
and `put(key, value)` Region operations, you could very well have implemented/mocked `putIfAbsent(key, value)` however
you wanted.  The Region object is a "_mock_" object after all.

Not only can you mock unsupported Region methods, you can also redefine the mocked behavior of a STDG supported
and mocked Region method, like `get(key)` or `put(key, value)` as well.

This capability applies to any GemFire/Geode mocked object. The choice is up to you what a GemFire/Geode mock object
does or does not do.

[[integration-testing]]
=== Integration Testing with STDG

You should write many more _Unit Tests_ than _Integration Tests_ to get reliable and fast feedback.  This is a
no brainer and software development 101.

However, _Unit Tests_ do not completely take the place of _Integration Tests_, either.  Both are necessary, as are
perhaps other forms of testing (e.g. Functional Testing, Acceptance Testing, Smoke Testing, Performance Testing,
Concurrency Testing, etc).

For instance, you should verify that the (OQL) Query you just constructed, maybe even generated, is well-formed
and yields the desired results, is performant, and all that jazz.  You can only reliably do that by executing
the (OQL) Query against an actual GemFire/Geode Region with a properly constructed and deliberate data set.

This sort _Integration Test_ does not have a complex arrangement, and can be performed simply by removing
or disabling the `@EnableGemFireMockObjects` annotation in our previous example above.

However, other forms of _Integration Testing_ might require a more complex arrangement,
such as client/server integration tests.

For instance, you may want to test that a client receives all the events from the server to which it has explicitly
registered interests.  For this type of test, you need to have a (1 or more) GemFire/Geode server(s) running,
and perhaps even a few clients.

Ideally, you want to fork a GemFire/Geode server JVM process in the _Integration Test_ class requiring
a server instance.

Once again, STDG comes to the rescue.

For example:

.Client/Server Integration Test
[source,java]
----
@RunWith(SpringRunner.class)
@ContextConfiguration(classes = GeodeClientTestConfiguration.class)
class ExampleIntegrationTestClass extends ForkingClientServerIntegrationTestsSupport {

  @BeforeClass
  public static void startGemFireServer() {
    startGemFireSever(GeodeServerTestConfiguration.class);
  }

  // test case method here

  @CacheServerApplication
  @EnableEntityDefinedRegions
  static class GeodeServerTestConfiguration {

    public static void main(String[] args) {

        AnnotationConfigApplicationContext applicationContext =
          new AnnotationConfigApplicationContext(GeodeServerTestConfiguration.class);

        applicationContext.registerShutdownHook();
    }
  }

  @ClientCacheApplication
  @EnableEntityDefinedRegions
  static class GeodeClientTestConfiguration { }

}
----

First we extend the STDG provided `ForkingClientServerIntegrationTestsSupport` class.  Then, we define a JUnit
`@BeforeClass` static setup method to fork our GemFire/Geode JVM process using the `GeodeServerTestConfiguration.class`
specifying exactly how the server should be configured and finally we create the matching `GeodeClientTestConfiguration`
class to configure and bootstrap our JUnit, Spring `TestContext` based test, which acts as the client.

STDG takes care of coordinating the client & server, using random connection ports, etc.  You simply just need to
provide the configuration of the client and server as required by your application and test case(s).

Here is 1
https://github.com/spring-projects/spring-boot-data-geode/blob/master/spring-geode-autoconfigure/src/test/java/org/springframework/geode/boot/autoconfigure/security/ssl/AutoConfiguredSslIntegrationTests.java[example]
of a concrete client/server _Integration Test_ extending STDG's `ForkingClientServerIntegrationTestsSupprt` class.

Notice, too, that I am using SDG's
https://docs.spring.io/spring-data/geode/docs/current/reference/html/#bootstrap-annotation-config[Annotation-based configuration model]
(e.g. `CacheServerApplication`, `@EnableEntityDefinedRegions`) to make the GemFire/Geode configuration even easier.

If you are using SBDG with this project, then some of the annotations are not even required (e.g. `ClientCacheApplication`).

When SBDG & STDG are combined, the power you have is quite extensive.

NOTE: Through the _Integration Test_ support provided by and in STDG is relatively simple, this is also not quite yet
the ideal way for writing client/sever _Integration Tests_.  Eventually, we want to include an annotation, something
like `@ClientServerIntegrationTest(serverConfigClass = GeodeServerTestConfiguration.class)`, the equivalent to
`@EnableGemFireMockObjects` for _Unit Testing_, to make configuration and testing of client/server applications
that much easier.  See https://github.com/spring-projects/spring-test-data-geode/issues/9[Issue #9] for more details.
This feature would be loosely based on, and similar to,
_Spring Boot_ https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-testing.html[Testing]
with _Test Slices_.

[[integration-testing-resource-cleanup]]
==== Cleaning up after GemFire/Geode during Integration Tests

When writing _Integration Tests_ using "live" GemFire/Geode objects (e.g. Regions), those object can leave artifacts
behind after a test run completes.

This can potentially cause conflicts between _Integration Test Cases_ that use features like persistence having
similarly named Regions particularly if you are not careful to differentiate the working directory between your tests.
This is also problematic, especially when switching between versions of GemFire/Geode, used by your application, during
testing. Perhaps you are in the middle of testing a (rolling) upgrade.

At any rate, STDG has you covered. If you would like to make sure that artifacts are properly cleaned up after a test
run, then you can annotate your test class with STDG's `@EnableGemFireResourceCollector` annotation, like so:

.Using `@EnableGemFireResourceCollector
[source,java]
----
@RunWith(SpringRunner.class)
@ContextConfiguration
class ExampleIntegrationTest {

	@CacheServerApplication
    @EnableLocator
    @EnableManager
    @EnableGemFireResourceCollector
    static class TestGeodeConfiguration { }

}
----

Like the `@EnableGemFireMockObjects` annotation, you can control which Spring `TestContext` test event will trigger
a GemFire/Geode resource (garbage) collection process using the `collectOnEvents` attribute.

Also, you can attempt to clean any GemFire/Geode `DiskStore` files (created by persistence, overflow or PDX) by setting
the `@EnableGemFireResourceCollector` annotation, `tryCleanDiskStoreFiles` attribute to `true`.

The following list of GemFire/Geode files with extensions or names are cleaned up by STDG's
`@EnableGemFireResourceCollector` functionality:

.GemFire/Geode File Extensions
|===
| File Extension | Description

| `.dat`
| Locator view file; e.g. `locator10334view.dat`

| `.gfs`
| Statistics archive file

| `.crf`
| Oplog file containing create, update, invalidate operations

| `.drf`
| Oplog file containing delete operations

| `.if`
| DiskStore metadata file

| `.krf`
| Oplog file for key and crf offset information

| `.lk`
| DiskStore access control file

| `.log`
| Log files created by GemFire/Geode process (Locators, Servers, Manager, etc)

| `.pid`
| File containing the OS process ID of the GemFire/Geode process (Locator, Server, etc)

| `.properties`
| GemFire/Geode properties configuration file (e.g. `gemfire.properties`)

| `.xml`
| GemFire/Geode XML configuration file (e.g. `cache.xml`)
|===

.GemFire/Geode Filenames
|===
| Filename | Description

| `backup`        | filename prefix
| `cache`         | filename prefix
| `configdiskdir` | _Cluster Configuration Service_ directory name
| `default`       | filename prefix
| `drlk_if`       | filename prefix
| `gfsecurity`    | filename prefix
| `gemfire`       | directory/file name
| `geode`         | directory/file name
| `locator`       | directory/file prefix name
| `overflow`      | filename prefix

|===

The names of file extensions and files/directories are treated by STDG as case insensitive when matching.

For a complete https://cwiki.apache.org/confluence/display/GEODE/Geode+Artifacts[list of artifacts] created by
GemFire/Geode processes, follow the link.


[[testing-logging-behavior]]
=== Asserting Logging Behavior

It is sometimes necessary or useful to write tests to assert an application's logging behavior.

For instance, if your application needs to log an event that occurred, output configuration meta-data on startup,
alert a user to some system event such as low memory, out of disk space, or a temporary network outage, or whatever
the case might be, it is useful to assert that your application logs an appropriate message.

But, how do you assert that certain log events with an appropriate log message has been made by the application
when the conditions constituting the log event have been arranged?

Now, STDG provides the capability to 1) assert that your application, or an application component, made a log event
at the appropriate moment and 2) that the log message communicates enough contextual-based information to be useful
to the user of your application.

To do this, STDG provides the `org.springframework.data.geode.tests.logging.slf4j.logback.TestAppender` class.

This Log Appender can be used when your application logging framework is configured with _Logback_ as the provider.

You declare the `TestAppender` in a `logback.xml` configuration file as follows:

.logback.xml configuration file
[source,xml]
----
<appender name="testAppender" class="org.springframework.data.gemfire.tests.logging.slf4j.logback.TestAppender">
    <encoder>
        <pattern>TEST - %m%n</pattern>
    </encoder>
</appender>
----

Then, the `TestAppender` can be used by registering it with a `Logger`:

.Logger using the TestAppender
[source,xml]
----
<logger name="example.app.net.service.NetworkService" level="WARN">
    <appender-ref ref="testAppender"/>
</logger>
----

For example, assume your application's `NetworkService` class uses the named `Logger` to log network events,
e.g. a DDoS attack:

.Application component with logging
[source,java]
----
@Service
class NetworkService {

    private final Logger logger = LoggerFactory.getLogger(NetworkService.class);

    void processDenialOfServiceAttack(NetworkEvent event) {

        logger.warn("A DDoS attack occured at {} from IP Address {}", event.getTime(), event.getIpAddress());

        // process the network event

        logger.warn("Another log message");
    }

    void processLoginRequest(LoginRequest request) {

        logger.info("User {} is attepting to login", request.getUser().getName());

        // process login request
    }
}
----

Then, it is a simple matter to test the logging behavior of your application by doing:

.Test logging behavior of the NetworkService class
[source,java]
----
class NetworkServiceUnitTests {

  private static TestAppender testAppender = TestAppender.getInstance();

  private NetworkService service;

  @Before
  public void setup() {
    this.service = new NetworkService();
  }

  @Test
  public void processDenialOfServiceAttackLogsNetworkEvent() {

    NetworkEvent event = new NetworkEvent();

    this.service.processDenialOfServiceAttack(event);

    assertThat(testAppender.lastLogMessage())
      .isEqualTo("A DDoS attack occurred at 2019-07-02 19:39:15 from IP Address 10.22.101.16");

    assertThat(testAppender.lastLogMessage())
      .isEqualTo("Another log message");

    assertThat(testAppender.lastLogMessage()).isNull();
  }

  @Test
  public void processLoginRequestDoesNotLogAnyMessageWithLogLevelSetToWarn() {

      LoginRequest request = new LoginRequest();

      this.service.processLoginRequest(request);

      assertThat(testAppender.lastLogMessage()).isNull();
  }
}
----

You may also clear any remaining, pending log messages from the in-memory queue (`Stack`)
by calling `TestAppender.clear()`.

All log message recorded by the `TestAppender` are stored from the most recent log event to the earliest log event.
Successively calling `TestAppender.lastLogMessage()` gets the most recent, last log message recorded first, then
the next log message recorded before the last, most recent log message and so on until no more log messages
for the operation under test exists, in which case `null` is returned from `lastLogMessage()` thereafter.


[[conclusion]]
=== Conclusion

Anyway, we hope this has intrigued your interests and gets you started for now.  Ideas, contributions, or other
feedback is most welcomed.

Thank you!