Add daily email for 2024-01-19

Tests can assert multiple things

source/_daily_emails/2024-01-19.md

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+---
+title: Tests can assert multiple things
+date: 2024-01-19
+permalink: archive/2024/01/19/tests-can-assert-multiple-things
+snippet: |
+  Should each automated test only have a single assertion?
+tags:
+  - software-development
+  - automated-testing
+  - test-driven-development
+---
+
+Similar to "a method should only have one return statement", I've seen similar advice when working with tests: "Tests should only have a single assertion".
+
+I don't think this is true, and in my experience, you need multiple assertions to have a thorough test.
+
+And, whilst similar assertions add some duplication, they can make the intent clearer and give better error messages.
+
+Instead, I focus on one test case per test.
+
+If I'm testing the following:
+
+* A blog page exists.
+* Only post nodes are visible.
+* Only published posts are visible,
+* Posts are returned in a specified order.
+
+These will be split into separate tests - making it easier to read and maintain the code and have faster execution times by running only the tests I want with the minimum amount of code in each - regardless of how many assertions are in each.