add doc

Signed-off-by: bowenlan-amzn <[email protected]>

Author: bowenlan-amzn

.github/workflows/test-and-build-workflow.yml

@@ -59,7 +59,7 @@ jobs:
       - name: Generate Jacoco Test Report
         if: always()
         run: |
-          su `id -un 1000` -c "./gradlew jacocoTestReport -Dtests.coverage=true"
+          su `id -un 1000` -c "./gradlew jacocoTestReport
       - name: Upload coverage XML
         uses: actions/upload-artifact@v4
         if: always()

DEVELOPER_GUIDE.md

@@ -5,6 +5,7 @@
     - [Setup](#setup)  
     - [Build](#build)
         - [Building from the command line](#building-from-the-command-line)
+        - [Code Coverage](#code-coverage)
         - [Debugging](#debugging)
     - [Using IntelliJ IDEA](#using-intellij-idea)
     - [Submitting Changes](#submitting-changes)
@@ -63,6 +64,31 @@ However, to build the `index management` plugin project, we also use the OpenSea
 
 When launching a cluster using one of the above commands, logs are placed in `build/testclusters/integTest-0/logs`. Though the logs are teed to the console, in practices it's best to check the actual log file.
 
+### Code Coverage
+
+The project supports generating code coverage reports using JaCoCo.
+
+#### Generating Coverage Reports
+
+To generate code coverage reports
+
+```bash
+./gradlew check -Dtests.coverage=true
+```
+
+Or run any tests, and generate test report
+
+```bash
+./gradlew test
+./gradlew jacocoTestReport
+```
+
+#### Coverage Report Locations
+
+After running with coverage enabled, reports are generated in:
+- **HTML Report**: `build/reports/jacoco/test/html/index.html` (human readable)
+- **XML Report**: `build/reports/jacoco/test/jacocoTestReport.xml` (for tools like Codecov)
+
 ### Debugging
 
 Sometimes it is useful to attach a debugger to either the OpenSearch cluster or the integ tests to see what's going on. When running unit tests, hit **Debug** from the IDE's gutter to debug the tests.  For the OpenSearch cluster or the integ tests, first, make sure start a debugger listening on port `5005`.