Basic documentation of how sanity tests work

src/cmd/sanity_test/README.md

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+# Sanity Tests
+
+A set of high-level blackbox tests designed to ensure the robustness of Corso's restore and export functionality.
+
+## Overview
+
+The purpose of sanity tests is to evaluate the restore and export capabilities of Corso, using OneDrive as an example. Here's a breakdown of how it works:
+
+1. **Setup:** Create a new folder in OneDrive, populate it with subfolders and files, and perform the initial backup.
+
+2. **Restore Testing:**
+   - Restore the backup to a different folder.
+   - Compare the original folder with the restored folder (eg: checking file names and sizes).
+   - Any mismatches are treated as failures.
+
+3. **Export Testing:**
+   - Export the backup to a local folder.
+   - Compare the exported data with the original data in OneDrive.
+
+## How to Run Locally
+
+Before running the tests locally, ensure your environment is connected to [M365](https://corsobackup.io/docs/setup/m365-access/) and [S3](https://corsobackup.io/docs/setup/repos/). Refer to the [quick start guide](https://corsobackup.io/docs/quickstart/) for detailed instructions.
+
+### Setting up Environment Variables
+
+For sanity tests, configure the following environment variables:
+
+#### For Restore:
+- `SANITY_TEST_SOURCE_CONTAINER`: Folder where the test data was created in OneDrive.
+- `SANITY_TEST_RESTORE_CONTAINER`: Folder where the test data will be restored in OneDrive.
+- `SANITY_BACKUP_ID`: ID of the Corso backup used for restore.
+
+#### For Export:
+- `SANITY_TEST_SOURCE_CONTAINER`: Folder where the test data was created.
+- `SANITY_TEST_RESTORE_CONTAINER`: Location of the exported data (local folder).
+- `SANITY_BACKUP_ID`: ID of the Corso backup used for restore.
+
+### Running Tests
+
+Once your environment is set up, execute the tests with the following command:
+
+```bash
+./sanity-test <restore|export> <service>
+```
+
+## CI run
+
+CI run is defined in `.github/workflows/sanity-test.yaml`. Check the
+[Actions](https://github.com/alcionai/corso/actions/workflows/sanity-test.yaml)
+ tab in this repository for detailed CI run logs.