Create end-to-end testing document (#132)

Create a separate document for end-to-end testing.

Author: dongsupark

README.md

@@ -39,17 +39,7 @@ This will run the unit tests for every library in the repository, not just for a
 Doing so ensures your testing will match what is run in the CI pipeline. 
 
 ### Running End-to-End (e2e) Tests
-End-to-end tests validate the integration of the entire system. These tests require additional setup, such as setting a subscription ID. To run e2e tests, use the following command from the repository root:
-
-```
-make e2e-test
-```
-
-This command will:
-
-1. Create a test user and associated SSH directory.
-2. Place mock SSH keys for testing.
-3. Run the tests and then clean up any test artifacts generated during the process.
+Please refer to [E2E_TESTING.md](docs/E2E_TESTING.md) for end-to-end testing.
 
 ## Contributing
 

docs/E2E_TESTING.md

@@ -0,0 +1,61 @@
+# Azure-init End-to-end Testing
+
+End-to-end tests validate the integration of the entire system. These tests require additional setup, such as setting a subscription ID.
+
+## Quickstart
+
+To run e2e tests, use the following command from the repository root:
+
+```
+make e2e-test
+```
+
+This command will:
+
+1. Create a test user and associated SSH directory.
+2. Place mock SSH keys for testing.
+3. Run the tests and then clean up any test artifacts generated during the process.
+
+## Details
+
+End-to-end testing of azure-init consists of 2 steps: preparation of SIG(Shared Image Gallery) image, and the actual testing.
+
+### Preparation of Azure SIG image
+
+To create an Azure SIG image to be used for end-to-end testing, run `image_creation.sh`.
+That will create a resource group, a storage account, a virtual machine, generate a SIG image, and publish the SIG image.
+
+```
+demo/image_creation.sh
+```
+
+If you want to run the script with custom variables for resource group, VM location, VM size, base image URN, etc., then specify corresponding environment variables. For example:
+
+```
+RG="mytest-azinit" LOCATION="westeurope" VM_SIZE="Standard_D2ds_v5" BASE_IMAGE="Canonical:0001-com-ubuntu-server-jammy:22_04-lts-gen2:latest" demo/image_creation.sh
+```
+
+The current limitation is, however, that the `BASE_IMAGE` should be one of Debian-derivatives like Ubuntu. When the build host OS is different from the target host OS, the `functional_test` binary might not be able to run due to mismatch of package versions such as glibc.
+
+### Running end-to-end testing
+
+To run end-to-end testing, use `make e2e-test`, which will create a test user, ssh directory, place mock ssh keys, and
+then clean up the test artifacts afterwards.
+
+`VM_IMAGE` should be specified to pick the correct SIG image created in the previous step.
+
+```
+VM_IMAGE="$(az sig image-definition list --resource-group testgalleryazinitrg --gallery-name testgalleryazinit | jq -r .[].id)" make e2e-test
+```
+
+It is also possible to pass custom environment variables. For example:
+
+```
+RG="mytest-azinit" LOCATION="westeurope" VM_SIZE="Standard_D2ds_v5" VM_IMAGE="$(az sig image-definition list --resource-group testgalleryazinitrg --gallery-name testgalleryazinit | jq -r .[].id)" make e2e-test
+```
+
+When testing is done, it is recommended to clean up resource group for SIG images.
+
+```
+az group delete --resource-group testgalleryazinitrg
+```