🚧 test(helm): add comprehensive unit tests for migrations and open sour…

mender/tests/README.md

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+# Mender Helm Chart Unit Tests
+
+This directory contains Helm unit tests for the Mender chart using [helm-unittest](https://github.com/helm-unittest/helm-unittest).
+
+## Test Suites
+
+### 1. Database Migrations (`migrations_test.yaml`)
+Tests the Helm hook migration jobs for database schema migrations.
+
+**Coverage:**
+- **Common migrations** (Open Source + Enterprise):
+  - device-auth, deployments, deviceconfig, deviceconnect
+  - inventory, iot-manager, useradm, workflows
+- **Enterprise-only migrations**:
+  - auditlogs, devicemonitor, tenantadm
+- **Verification:**
+  - Jobs are created when `dbmigration.enable: true`
+  - Jobs respect service enabled/disabled state
+  - Enterprise migrations only run when `global.enterprise: true`
+  - Correct Helm hook annotations (pre-install, pre-upgrade)
+  - Correct hook weight and delete policy
+
+### 2. Open Source Backing Services (`opensource-backing-services_test.yaml`)
+Tests the integrated MongoDB deployment for open source installations.
+
+**Coverage:**
+- **MongoDB Deployment:**
+  - Creation when `mongodb.enabled: true`
+  - Container configuration (image, env vars, ports)
+  - Health probes (liveness, readiness)
+  - Volume mounts (data persistence)
+- **MongoDB Service:**
+  - ClusterIP service on port 27017
+  - Correct selectors
+- **MongoDB Secret:**
+  - Root password stored as base64
+- **MongoDB PersistentVolumeClaim:**
+  - Created when `mongodb.persistence.enabled: true`
+  - Storage class configuration
+  - Access modes and size
+
+### 3. NATS Integration (`nats-integration_test.yaml`)
+Tests the NATS message broker integration for open source installations.
+
+**Coverage:**
+- **NATS Environment Variables:**
+  - WORKFLOWS_NATS_URI configuration
+  - WORKFLOWS_NATS_STREAM_REPLICAS configuration
+- **Configuration Modes:**
+  - Integrated NATS (nats.enabled: true)
+  - External NATS (via global.nats.URL)
+  - NATS credentials from existing secret
+- **Open Source Defaults:**
+  - NATS enabled by default
+  - JetStream replicas configured correctly
+
+### 4. Workflows HPA (`workflows-hpa_test.yaml`)
+Tests the Horizontal Pod Autoscaler for the workflows service.
+
+**Coverage:**
+- HPA creation conditions
+- External metrics configuration
+- Scale behavior policies
+- Replica configuration
+
+## Running Tests
+
+### Run all tests:
+```bash
+helm unittest mender
+```
+
+### Run specific test suite:
+```bash
+helm unittest mender --file 'tests/migrations_test.yaml'
+helm unittest mender --file 'tests/opensource-backing-services_test.yaml'
+helm unittest mender --file 'tests/nats-integration_test.yaml'
+helm unittest mender --file 'tests/workflows-hpa_test.yaml'
+```
+
+## Test Statistics
+
+- **Total Test Suites:** 4
+- **Total Tests:** 61
+- **Coverage:**
+  - Database migrations: 20 tests
+  - MongoDB (Open Source): 25 tests
+  - NATS integration: 7 tests
+  - Workflows HPA: 9 tests
+
+## Open Source vs Enterprise
+
+The tests verify that the correct backing services are deployed based on the deployment type:
+
+### Open Source Deployment
+- **Integrated MongoDB** (`mongodb.enabled: true`)
+- **Integrated NATS** (`nats.enabled: true`)
+- **8 common migration jobs**
+
+### Enterprise Deployment
+- **External MongoDB** (via connection string)
+- **External NATS** (via `global.nats.URL`)
+- **11 migration jobs** (8 common + 3 enterprise-only)
+
+## Prerequisites
+
+Install the helm-unittest plugin:
+```bash
+helm plugin install https://github.com/helm-unittest/helm-unittest
+```