Added documentation about FilePath and removed wip status (#7783)

added documentation about FilePath and removed wip status

content/doc/developer/testing/index.adoc

@@ -1,7 +1,6 @@
 ---
 title: Testing
 layout: developerchapter
-wip: true
 references:
 - url: https://wiki.jenkins.io/display/JENKINS/Mocking+in+Unit+Tests
   title: "Wiki: Mocking in Unit Tests"
@@ -357,7 +356,12 @@ public class PipelineWorkspaceExampleTest {
 <1> The path to the zip file is dynamic, so we pass it into the Pipeline definition.
 
 ===== Using `FilePath`
-TODO: Expand this section, and explain the below example.
+
+In Jenkins plugin development, the link:https://javadoc.jenkins.io/hudson/FilePath.html[`FilePath`] class is a key utility used to interact with files and directories on the nodes where Jenkins jobs execute.
+Unlike the basic `File`, it allows plugin developers to work seamlessly with files across controller and agent nodes, handling the distribution and access to remote resources.
+
+In test scenarios, you often need to set up a controlled environment with specific files or directories.
+You can use `FilePath` to create them and use the method `copyFrom()` to place the data from FileItem into the file location specified by this FilePath object:
 
 [source,java]
 ----
@@ -366,6 +370,13 @@ FilePath report = workspace.child("target").child("lint-results.xml");
 report.copyFrom(getClass().getResourceAsStream("lint-results_r20.xml"));
 ----
 
+If you want to create files or folder remotely on an agent node, the below example shows how to use it:
+[source,java]
+----
+FilePath remotePath = new FilePath(agentChannel, "/remote/path/file.txt");
+remotePath.write("Remote Content", "UTF-8");
+----
+
 ==== Customizing the `JENKINS_HOME` Directory
 
 If you want to adjust the `JENKINS_HOME` within a test, use the `JenkinsRule`-methods link:https://javadoc.jenkins.io/component/jenkins-test-harness/org/jvnet/hudson/test/JenkinsRule.html#withExistingHome(java.io.File)[`withExistingHome()`] or link:https://javadoc.jenkins.io/component/jenkins-test-harness/org/jvnet/hudson/test/JenkinsRule.html#withNewHome()[`withNewHome()`].