fix: change step name to avoid duplicate heading and add testing docs

- Change step name from 'Summary' to 'Output' to prevent duplication with job name
- Add comprehensive Testing section to README with local and CI/CD instructions
- Document architecture limitations for local testing

Author: moizpgedge

.github/workflows/test_images.yaml

@@ -125,7 +125,7 @@ jobs:
     runs-on: ubuntu-latest
     if: always()
     steps:
-      - name: Summary
+      - name: Output
         run: |
           echo "| Input | Value |" >> $GITHUB_STEP_SUMMARY
           echo "|-------|-------|" >> $GITHUB_STEP_SUMMARY

README.md

@@ -112,3 +112,54 @@ volumes:
 - Mutable tags also exist for:
   - The latest image for a given Postgres major.minor + spock major version, `pg<postgres major.minor>-spock<major>-<flavor>` , e.g. `17.6-spock5-standard`
   - The latest image for a given Postgres major + spock major version, `pg<postgres major>-spock<major>-<flavor>`, e.g. `17-spock5-standard`
+
+## Testing
+
+This repository includes a comprehensive test suite to validate Postgres images. The tests verify:
+- Default entrypoint functionality
+- Patroni entrypoint (standard images only)
+- PostgreSQL connectivity and version checks
+- Extension availability and functionality (Spock, LOLOR, Snowflake, pgvector, PostGIS, pgaudit)
+- pgBackRest installation (standard images only)
+
+### Running Tests Locally
+
+To run tests locally, you'll need:
+- Go 1.24.11 or later
+- Docker installed and running
+- Access to pull the image you want to test
+
+Run the test suite using the Makefile:
+
+```bash
+make test-image IMAGE=<image> FLAVOR=<minimal|standard>
+```
+
+Example:
+
+```bash
+make test-image IMAGE=ghcr.io/pgedge/pgedge-postgres:17-spock5-standard FLAVOR=standard
+```
+
+Or run directly with Go:
+
+```bash
+cd tests && go run main.go -image <image> -flavor <minimal|standard>
+```
+
+### Local Testing Limitations
+
+**Architecture Limitations:** When running tests locally, you can only test images that match your local machine's architecture. For example:
+- On an x86_64/amd64 machine, you can only test amd64 images
+- On an ARM64 machine, you can only test arm64 images
+
+To test images for multiple architectures (x86 and ARM), use the GitHub Actions workflow which runs tests on both `ubuntu-latest` (x86) and `ubuntu-24.04-arm` (ARM) runners.
+
+### CI/CD Testing
+
+The GitHub Actions workflow (`.github/workflows/test_images.yaml`) can be triggered manually to test images across multiple architectures. The workflow accepts:
+- **Package Repository**: The container registry repository name
+- **Tags**: Comma-separated list of image tags to test
+- **Architectures**: Comma-separated list of architectures (`x86,arm`)
+
+The workflow will automatically test each tag on each specified architecture.