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