---
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title: "Introducing: How to Mock Outbound Http Calls for Easier Testing (2025 release wave 1)"
summary: "HTTP client Handler for mocking outbound HTTP calls in AL tests (2025 release wave 1). Covers intercepting requests, simulating responses, telling requests apart, the fall-through mechanism, and the test HTTP request policy options. Known limits: no cookies or redirection status codes."
tier: official
language: en
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  - http client handler
  - al test
  - external services
  - test isolation
  - request interception
  - fall-through mechanism
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source_name: Microsoft Dynamics 365 Business Central (YouTube)
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    text: however this setup requires that the external service is up and running instead we can define an HTTP client hander to intercept the request
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---

# Introducing: How to Mock Outbound Http Calls for Easier Testing (2025 release wave 1)

> HTTP client Handler for mocking outbound HTTP calls in AL tests (2025 release wave 1). Covers intercepting requests, simulating responses, telling requests apart, the fall-through mechanism, and the test HTTP request policy options. Known limits: no cookies or redirection status codes.

[Watch on YouTube](https://www.youtube.com/watch?v=JI9OpaBx0nk) · Microsoft Dynamics 365 Business Central (YouTube) · 2025-04-01 · 10:40 · tier official · reviewed (checked by Opus)

## Overview

The video explains why testing code that calls external services is hard: tests depend on the service being up, and running them against a live service can affect production. It introduces a new test Handler, the HTTP client Handler, which intercepts outbound HTTP requests during test execution so the test can return a mocked response instead.

The demo shows how to set up the Handler, attach it to a test with the Handler functions attribute, and use request properties to return different responses. It then covers the fall-through mechanism for mixing mocked and real calls, a live debugging session, and the test HTTP request policy that controls which outbound requests are allowed.

## Key points

- Mark a procedure with the HTTP client Handler attribute and attach it to a test with the Handler functions attribute; all HTTP calls during that test are then routed to the Handler.
- The request object exposes request type, path, query parameters and a has-secret-URI property, which you can use to return different responses per request.
- When the request URI is set using secret text, path and query parameters are not available.
- Fall-through: the Handler returns a Boolean. Exit true issues the original request; exit false (the default) uses the mocked response, so an empty Handler still blocks the outbound call.
- Test HTTP request policy on a test codeunit has three options: allow all outbound requests (default), allow outbound only from the Handler, or block all outbound requests.
- Blocking outbound requests is suggested for automated CI/CD pipelines so tests never hit real endpoints.
- As of now, cookies and redirection status codes cannot be set in mocked responses.

## Chapters

- [0:00](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=0s) Testing challenges with external services
- [1:25](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=85s) Introducing HTTP client Handler
- [2:26](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=146s) Setting up the Handler and simulating responses
- [3:25](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=205s) Distinguishing between different requests
- [4:21](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=261s) Handling secret URIs and limitations
- [5:16](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=316s) Fall-through mechanism for selective mocking
- [6:14](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=374s) Live debugging demonstration
- [8:20](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=500s) Test HTTP request policy and scenarios

## Features

Every feature below: status not stated, demoed.

| Feature | At |
|---|---|
| HTTP client Handler | [1:25](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=85s) |
| HTTP client Handler attribute | [2:26](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=146s) |
| Handler functions attribute | [2:44](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=164s) |
| Request object properties | [3:45](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=225s) |
| Fall-through mechanism | [5:16](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=316s) |
| Test HTTP request policy | [8:20](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=500s) |
| Allow all outbound requests policy | [8:52](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=532s) |
| Allow outbound from Handler policy | [9:32](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=572s) |
| Block outbound requests policy | [10:08](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=608s) |

## AL objects mentioned

As heard in the captions. A name that matches one object page by exact type and name links to it; the others stay as named.

- other "document service" at [1:46](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=106s)
- codeunit "test code unit" at [2:06](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=126s)
- other "response object" at [2:26](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=146s)
- other "request object" at [3:45](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=225s)

Not found in BC28-30: codeunit "test code unit".

## Quotes

- [0:04](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=4s) "if we connect to the actual service we need to consider how that service will be impacted by running tests will it impact production"
- [1:25](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=85s) "to address many of these challenges we have introduced a new test Handler in this release the HTTP client Handler"
- [2:06](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=126s) "however this setup requires that the external service is up and running instead we can define an HTTP client hander to intercept the request"
- [4:21](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=261s) "it is important to mention that as of now it is not possible to set cookies or redirection status codes so far so good"
- [5:16](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=316s) "we have implemented a fall through mechanism that allows the programmer to decide in the Handler whether they want to Mark the response for"
- [5:53](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=353s) "keep in mind that the default return value is false therefore a completely empty hander procedure would still block the outbound request and return"
- [8:31](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=511s) "you can add it to test code units to specify how outbound request should be treated during test executions by default all requests are"

## Disclaimers in the video

- [4:21](https://www.youtube.com/watch?v=JI9OpaBx0nk&t=261s) other: as of now it is not possible to set cookies or redirection status codes

Presenters (as heard): Stefan, Balash.