Add docs.

docs/src/main/asciidoc/verifier_faq.adoc

@@ -634,7 +634,7 @@ In order to do that, use the usual producer setup, and then add the `pushStubsTo
 
 On the consumer side when passing the `repositoryRoot` parameter,
 either from the `@AutoConfigureStubRunner` annotation, the
-JUnit rule or properties, it's enough to pass the URL of the
+JUnit rule, JUnit 5 extension or properties, it's enough to pass the URL of the
 SCM repository, prefixed with the protocol. For example
 
 [source,java,indent=0]
@@ -868,9 +868,9 @@ logging.level.com.github.tomakehurst.wiremock=ERROR
 
 ==== How can I see what got registered in the HTTP server stub?
 
-You can use the `mappingsOutputFolder` property on `@AutoConfigureStubRunner` or `StubRunnerRule`
-to dump all mappings per artifact id. Also the port at which the given stub server was
-started will be attached.
+You can use the `mappingsOutputFolder` property on `@AutoConfigureStubRunner`, `StubRunnerRule` or
+`StubRunnerExtension`to dump all mappings per artifact id. Also the port at which the given stub server
+was started will be attached.
 
 ==== Can I reference text from file?
 

spring-cloud-contract-stub-runner/README.adoc

@@ -267,7 +267,7 @@ mappings available for the given server:
 
 Depending on the provided Stub Runner dependency and the DSL the messaging routes are automatically set up.
 
-=== Stub Runner JUnit Rule
+=== Stub Runner JUnit Rule and Stub Runner JUnit5 Extension
 
 Stub Runner comes with a JUnit rule thanks to which you can very easily download and run stubs for given group and artifact id:
 
@@ -276,7 +276,8 @@ Stub Runner comes with a JUnit rule thanks to which you can very easily download
 include::src/test/groovy/org/springframework/cloud/contract/stubrunner/junit/StubRunnerRuleJUnitTest.java[tags=classrule]
 ----
 
-After that rule gets executed Stub Runner connects to your Maven repository and for the given list of dependencies tries to:
+There's also a `StubRunnerExtension` available for JUnit 5. `StubRunnerRule` and `StubRunnerExtension` work in a very
+similar fashion. After the rule/ extension is executed, Stub Runner connects to your Maven repository and for the given list of dependencies tries to:
 
 - download them
 - cache them locally
@@ -288,7 +289,7 @@ After that rule gets executed Stub Runner connects to your Maven repository and
 Stub Runner uses https://wiki.eclipse.org/Aether[Eclipse Aether] mechanism to download the Maven dependencies. 
 Check their https://wiki.eclipse.org/Aether[docs] for more information.
 
-Since the `StubRunnerRule` implements the `StubFinder` it allows you to find the started stubs:
+Since the `StubRunnerRule` and `StubRunnerExtension` implement the `StubFinder` they allow you to find the started stubs:
 
 [source,groovy,indent=0]
 ----
@@ -309,11 +310,18 @@ Example of usage in JUnit tests:
 include::src/test/groovy/org/springframework/cloud/contract/stubrunner/junit/StubRunnerRuleJUnitTest.java[tags=test]
 ----
 
+JUnit 5 Extension example:
+
+[source,java,indent=0]
+----
+include::src/test/java/org/springframework/cloud/contract/stubrunner/junit/StubRunnerJUnit5ExtensionTest.java[tags=extension]
+----
+
 Check the *Common properties for JUnit and Spring* for more information on how to apply global configuration of Stub Runner.
 
-IMPORTANT: To use the JUnit rule together with messaging you have to provide an implementation of the
+IMPORTANT: To use the JUnit rule or JUnit 5 extension together with messaging, you have to provide an implementation of the
 `MessageVerifier` interface to the rule builder (e.g. `rule.messageVerifier(new MyMessageVerifier())`).
-If you don't do this then whenever you try to send a message an exception will be thrown.
+If you don't do this, then whenever you try to send a message an exception will be thrown.
 
 ==== Maven settings
 
@@ -327,7 +335,7 @@ JUnit rule.
 
 ==== Fluent API
 
-When using the `StubRunnerRule` you can add a stub to download and then pass the port for the last downloaded stub.
+When using the `StubRunnerRule` or `StubRunnerExtension` you can add a stub to download and then pass the port for the last downloaded stub.
 
 [source,java,indent=0]
 ----

spring-cloud-contract-stub-runner/src/test/java/org/springframework/cloud/contract/stubrunner/junit/StubRunnerJUnit5ExtensionTest.java

@@ -41,6 +41,7 @@ class StubRunnerJUnit5ExtensionTest {
         System.clearProperty("stubrunner.classifier");
     }
 
+    // tag::extension[]
     // Visible for Junit
     @RegisterExtension
     static StubRunnerExtension stubRunnerExtension = new StubRunnerExtension()
@@ -60,6 +61,7 @@ class StubRunnerJUnit5ExtensionTest {
         assertThat(stubRunnerExtension
                 .findStubUrl("org.springframework.cloud.contract.verifier.stubs:fraudDetectionServer")).isNotNull();
     }
+    // end::extension[]
 
     @Test
     void should_output_mappings_to_output_folder() {