azure-functions-tests

Overview

Azure Functions Core Tools v4 (func.exe) provides a local runtime that mirrors the Functions host on Azure. Per learn.microsoft.com/azure/azure-functions/functions-run-local, func start starts all triggers in the project directory and outputs the URL of every HTTP-triggered function. Azurite emulates Blob, Queue, and Table Storage locally so queue and timer triggers can be exercised without a live storage account.

Nearest neighbours and how this skill differs:

• aws-sam-local-testing wraps SAM Local for Lambda/API Gateway (its references/dotnet.md covers the .NET Lambda test runner). This skill is Azure-only and covers func start, Azurite, the .NET isolated worker model (Microsoft.Azure.Functions.Worker), and admin-endpoint invocation.
• serverless-integration-test-builder builds multi-function integration harnesses. This skill covers the per-function local invocation workflow.

When to use

• Local unit + integration tests for Azure Function handlers before deploy.
• Reproducing HTTP, queue, or timer trigger behaviour without deploying.
• CI gating on function handler logic in .NET, Node.js, or Python.
• Verifying binding configuration with Azurite instead of live Azure Storage.

How to use

1. Install Core Tools v4 (func --version shows 4.x) and Azurite, then scaffold with func init and add triggers with func new - commands in references/local-setup.md.
2. Set AzureWebJobsStorage to UseDevelopmentStorage=true in local.settings.json so queue and timer triggers route to Azurite; keep the file git-ignored.
3. Start Azurite, then run func start from the project root and note the printed HTTP trigger URLs.
4. Exercise HTTP triggers with curl; fire non-HTTP (queue/timer) triggers through the /admin/functions/<name> endpoint - see references/triggering-functions.md.
5. Unit-test handler logic directly (no running host) with the per-language patterns in references/unit-testing-handlers.md.
6. Wire Core Tools + Azurite + dotnet test / pytest / npm test into CI using the workflow in references/triggering-functions.md.
7. Confirm binding config against Azurite; verify Managed Identity / RBAC in a staging environment (see Limitations).

Reference files

• Install, project init, local.settings.json, Azurite, and func start: references/local-setup.md.
• Firing HTTP / queue / timer triggers and the CI workflow: references/triggering-functions.md.
• Unit-testing handlers in .NET isolated, Node.js v4, and Python v2: references/unit-testing-handlers.md.

Worked example

A .NET isolated function OrderProcessor is triggered by the orders queue. To gate it locally before deploy:

1. func init OrderApp --worker-runtime dotnet-isolated, then func new --template "Azure Queue Storage Trigger" --name OrderProcessor.

2. In local.settings.json, set "AzureWebJobsStorage": "UseDevelopmentStorage=true".

3. Run azurite --silent --location ./azurite-data in one shell and func start in another.

4. Fire the trigger through the admin endpoint:

   curl --request POST -H "Content-Type: application/json" \
        --data '{"input":"{\"orderId\":42}"}' \
        http://localhost:7071/admin/functions/OrderProcessor

   The host returns HTTP 202 (Accepted) and the function logs the processed order.

5. Unit-test OrderProcessor.Run with a mocked FunctionContext (xUnit), asserting the parsed order id - no host required.

Result: queue-trigger wiring is verified against Azurite and handler logic is gated in CI, with no live Azure Storage account.

Anti-patterns

Limitations

• Azurite does not emulate Azure Files or Azure Data Lake Storage Gen2, per learn.microsoft.com/azure/storage/common/storage-use-azurite. Functions that use these services must connect to live Azure Storage during local testing.
• Event Grid triggers require extra configuration to run locally; the admin-endpoint approach does not cover them. See learn.microsoft.com/azure/azure-functions/functions-run-local#run-a-local-function for the viewer web app approach.
• Managed Identity authentication and RBAC roles cannot be replicated by func start. Test with connection strings locally; verify RBAC in a staging environment.
• Cold-start behaviour differs from production. For cold-start budgets see cold-start-budget-reference.

References

• Core Tools install and func start: learn.microsoft.com/azure/azure-functions/functions-run-local
• Local development overview: learn.microsoft.com/azure/azure-functions/functions-develop-local
• .NET isolated worker model guide: learn.microsoft.com/azure/azure-functions/dotnet-isolated-process-guide
• In-process vs isolated model comparison: learn.microsoft.com/azure/azure-functions/dotnet-isolated-in-process-differences
• Azurite install and run: learn.microsoft.com/azure/storage/common/storage-install-azurite
• Azurite emulator overview: learn.microsoft.com/azure/storage/common/storage-use-azurite
• Manually run non-HTTP triggers: learn.microsoft.com/azure/azure-functions/functions-manually-run-non-http
• Sibling skills: aws-sam-local-testing, cold-start-budget-reference, cloudflare-workers-miniflare, serverless-integration-test-builder