Add daily email for 2024-06-05

Writing assertions first

source/_daily_emails/2024-06-05.md

@@ -0,0 +1,71 @@
+---
+title: Writing assertions first
+date: 2024-06-05
+permalink: daily/2024/06/05/writing-assertions-first
+tags:
+    - software-development
+    - automated-testing
+    - test-driven-development
+cta: testing_course
+snippet: |
+    Sometimes, I write my test assertions first.
+---
+
+As well as [writing comments first][0], when writing tests, I sometimes like to write my tests backwards and start by writing the assertions first.
+
+I know what I want to assert in the test, so it's an easy place to start.
+
+I'll run it, see the error, fix it and continue working backwards.
+
+For example, I could start with this:
+
+```php
+public function testOnlyPostNodesAreShown(): void {
+  $assert = $this->assertSession();
+  $assert->pageTextContains('Post one');
+  $assert->pageTextContains('Post two');
+  $assert->pageTextNotContains('This is not a post');
+}
+```
+
+This test will fail when I run it, but it makes me think about what I need to do to fix the error and how to do so in the best way.
+
+In this case, I need to make a request to the page that should render the text:
+
+```php
+public function testOnlyPostNodesAreShown(): void {
+  $this->drupalGet('/blog');
+
+  $assert = $this->assertSession();
+  $assert->pageTextContains('Post one');
+  $assert->pageTextContains('Post two');
+  $assert->pageTextNotContains('This is not a post');
+}
+```
+
+This will still fail, as I also need to create the required posts:
+
+```php
+public function testOnlyPostNodesAreShown(): void {
+  PostBuilder::create()->setTitle('Post one')->getPost();
+  PostBuilder::create()->setTitle('Post two')->getPost();
+
+  $this->createNode([
+    'title' => 'This is not a post',
+    'type' => 'page',
+  ]);
+
+  $this->drupalGet('/blog');
+
+  $assert = $this->assertSession();
+  $assert->pageTextContains('Post one');
+  $assert->pageTextContains('Post two');
+  $assert->pageTextNotContains('This is not a post');
+}
+```
+
+Now the test passes.
+
+Doing test-driven development keeps my code clean and minimal, and I find this approach keeps my test clean, too.
+
+[0]: {{site.url}}/daily/2024/06/03/writing-comments-first