diff --git a/plugin/skills/azure-prepare/references/services/functions/templates/recipes/common/testing.md b/plugin/skills/azure-prepare/references/services/functions/templates/recipes/common/testing.md
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@@ -0,0 +1,129 @@
+# Testing Azure Functions
+
+Common pitfalls and best practices when testing Azure Functions after deployment.
+
+## Route Prefix
+
+> ⚠️ **Critical: Azure Functions use `/api/` prefix by default**
+
+All HTTP-triggered functions have routes prefixed with `/api/` unless explicitly overridden.
+
+| Route Attribute | Actual URL |
+|-----------------|------------|
+| `Route = "shorten"` | `https://{host}/api/shorten` |
+| `Route = "r/{id}"` | `https://{host}/api/r/{id}` |
+| `Route = "health"` | `https://{host}/api/health` |
+
+### Option 1: Test with `/api/` prefix (default)
+
+```bash
+# Correct - includes /api/
+curl https://func-app.azurewebsites.net/api/shorten
+
+# Wrong - missing /api/, returns 404
+curl https://func-app.azurewebsites.net/shorten
+```
+
+### Option 2: Remove prefix via host.json
+
+Add to `host.json` to remove the `/api/` prefix:
+
+```json
+{
+  "version": "2.0",
+  "extensions": {
+    "http": {
+      "routePrefix": ""
+    }
+  }
+}
+```
+
+After this change:
+- `Route = "shorten"` → `https://{host}/shorten`
+- `Route = "r/{id}"` → `https://{host}/r/{id}`
+
+**Recommendation**: Set `routePrefix: ""` for cleaner URLs, especially for URL shorteners and public APIs.
+
+## Cold Start Delays
+
+Flex Consumption and Consumption plans scale to zero when idle. First request after idle triggers a cold start:
+
+| Plan | Typical Cold Start |
+|------|-------------------|
+| Flex Consumption | 1-5 seconds |
+| Consumption (Y1) | 5-15 seconds |
+| Premium | ~0 (always warm) |
+
+**Testing strategy:**
+```bash
+# First request may timeout or be slow
+curl --max-time 30 https://func-app.azurewebsites.net/api/health
+
+# Subsequent requests are fast
+curl https://func-app.azurewebsites.net/api/health
+```
+
+## RBAC Propagation Delays
+
+Azure RBAC role assignments take 30-60 seconds to propagate. Functions accessing Azure resources (Storage, Cosmos DB, Event Hubs) may fail with 401/403 immediately after deployment.
+
+**Two-phase deployment strategy:**
+```bash
+# Phase 1: Provision infrastructure + RBAC
+azd provision --no-prompt
+
+# Wait for RBAC propagation
+sleep 60
+
+# Phase 2: Deploy code
+azd deploy --no-prompt
+```
+
+**Symptoms of RBAC not propagated:**
+- 401 Unauthorized
+- 403 Forbidden
+- "AuthorizationPermissionMismatch" errors
+- Storage or Cosmos operations failing silently
+
+## Testing Checklist
+
+Before reporting a function as broken, verify:
+
+- [ ] **Route**: Using correct URL with or without `/api/` prefix
+- [ ] **Cold start**: Waited for first request to complete (up to 30s)
+- [ ] **RBAC**: Waited 60s after provision for role assignments to propagate
+- [ ] **App settings**: Verified settings are deployed (`az functionapp config appsettings list`)
+- [ ] **Logs**: Checked Application Insights for actual errors
+
+## Sample Test Script
+
+```bash
+#!/bin/bash
+FUNC_URL="https://func-app.azurewebsites.net"
+
+echo "Testing health endpoint..."
+curl -s --max-time 30 "$FUNC_URL/api/health" || echo "Cold start - retrying..."
+sleep 5
+curl -s "$FUNC_URL/api/health"
+
+echo -e "\nTesting create endpoint..."
+RESULT=$(curl -s -X POST "$FUNC_URL/api/shorten" \
+  -H "Content-Type: application/json" \
+  -d '{"url": "https://example.com"}')
+echo "$RESULT"
+
+SHORT_CODE=$(echo "$RESULT" | jq -r '.shortCode')
+echo -e "\nTesting redirect for $SHORT_CODE..."
+curl -i "$FUNC_URL/api/r/$SHORT_CODE"
+```
+
+## Common Errors
+
+| Error | Likely Cause | Solution |
+|-------|--------------|----------|
+| 404 Not Found | Wrong route (missing `/api/`) | Check route prefix |
+| 401 Unauthorized | RBAC not propagated | Wait 60s, check role assignments |
+| 403 Forbidden | Missing RBAC role | Verify role assignment exists |
+| 500 Internal Error | App setting missing | Check app configuration |
+| Empty response | Function crashed | Check Application Insights logs |
diff --git a/plugin/skills/azure-prepare/references/services/functions/templates/recipes/composition.md b/plugin/skills/azure-prepare/references/services/functions/templates/recipes/composition.md
index 6ead0700f..77611220d 100644
--- a/plugin/skills/azure-prepare/references/services/functions/templates/recipes/composition.md
+++ b/plugin/skills/azure-prepare/references/services/functions/templates/recipes/composition.md
@@ -217,6 +217,25 @@ azd deploy --no-prompt        # Deploy code (RBAC now active)
 > **CRITICAL: Never enable `allowSharedKeyAccess: true`** as a workaround for 403 errors.
 > The correct solution is waiting for RBAC propagation, not disabling security.
 
+### Step 8: Test the Deployment
+
+> ⚠️ **MANDATORY: Read [common/testing.md](common/testing.md) before testing**
+>
+> Common pitfalls that cause false "broken" reports:
+> - **Route prefix**: Functions use `/api/` prefix by default. Test `https://host/api/shorten`, not `https://host/shorten`
+> - **Cold start**: First request may take 5-30 seconds on Consumption plans
+> - **RBAC delay**: Wait 60 seconds after provision before testing RBAC-dependent operations
+
+**Quick test example:**
+```bash
+# Note: /api/ prefix is required unless routePrefix is set to "" in host.json
+FUNC_URL="https://func-app.azurewebsites.net"
+
+# Test with correct /api/ prefix
+curl "$FUNC_URL/api/health"
+curl -X POST "$FUNC_URL/api/shorten" -H "Content-Type: application/json" -d '{"url":"https://example.com"}'
+```
+
 ## Base Template Lookup
 
 | Language | Bicep Template | Terraform Template |