docs(daily-email): add 2023-11-23

Partial mocking

src/content/daily-email/2023-11-23.md

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+---
+title: >
+  Partial mocking
+pubDate: 2023-11-23
+permalink: >
+  archive/2023/11/23/partial-mocking
+tags:
+  - automated-testing
+  - test-driven-development
+  - drupal
+  - php
+  - phpunit
+  - phpc
+---
+
+Today, I wrote a test whilst fixing a bug in some legacy custom Drupal code.
+
+The code is for a custom block, which can be configured using user-defined settings - including a link URL.
+
+In this case, if the link was null (one hadn't been provided), the link was generated to the home page instead of the desired destination.
+
+## My first attempt
+
+There was a combination of settings needed to replicate the bug, such as the current site language, the node type the block was placed on and, of course, an empty link URL.
+
+Because the block uses the current route to get the current node, my first attempt to test this was to use a browser/functional test.
+
+That failed quickly after having to enable various other custom modules due to dependencies and to add and configure unrelated configuration settings.
+
+## My second attempt
+
+My second attempt used kernel/integration tests, but as there's no `setParameter()` method on the route matcher I could use in the test, I'd need to rely on mocking.
+
+In a unit test, everything needs to be mocked, but a kernel test allows me to be more selective, only mock what I need, and use the real services for everything else - a.k.a. partial mocking.
+
+## The result
+
+I replicated the bug by setting the default and current languages, creating a mock language manager, creating a node of the required type and returning it from a mocked route match.
+
+Everything else remained the same.
+
+Then, I fixed the bug and used a data provider to provide different variables into the test so each use case was covered.
+
+## Here's the thing
+
+The whole test file is 129 lines and would have been much more if I'd had to replicate all the configuration in a functional test or mock everything in a unit test.
+
+An integration test with partial mocking was ideal in this case, as it gave me the most flexibility to test what I needed whilst keeping the code simple.
+
+Whilst I'm aware of over-using mocks, this was an ideal situation to use them.