oliverdavies.uk/content/node.066297b1-ab00-4769-afe1-d3831ed2a654.yml

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title:
  - value: 'Writing assertions first'
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  - value: '2024-06-05T00:00:00+00:00'
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body:
  - value: |
      <p>As well as <a href="/daily/2024/06/03/writing-comments-first">writing comments first</a>, when writing tests, I sometimes like to write my tests backwards and start by writing the assertions first.</p>

      <p>I know what I want to assert in the test, so it's an easy place to start.</p>

      <p>I'll run it, see the error, fix it and continue working backwards.</p>

      <p>For example, I could start with this:</p>

      <pre><code class="php">public function testOnlyPostNodesAreShown(): void {
        $assert = $this-&gt;assertSession();
        $assert-&gt;pageTextContains('Post one');
        $assert-&gt;pageTextContains('Post two');
        $assert-&gt;pageTextNotContains('This is not a post');
      }
      </code></pre>

      <p>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.</p>

      <p>In this case, I need to make a request to the page that should render the text:</p>

      <pre><code class="php">public function testOnlyPostNodesAreShown(): void {
        $this-&gt;drupalGet('/blog');

        $assert = $this-&gt;assertSession();
        $assert-&gt;pageTextContains('Post one');
        $assert-&gt;pageTextContains('Post two');
        $assert-&gt;pageTextNotContains('This is not a post');
      }
      </code></pre>

      <p>This will still fail, as I also need to create the required posts:</p>

      <pre><code class="php">public function testOnlyPostNodesAreShown(): void {
        PostBuilder::create()-&gt;setTitle('Post one')-&gt;getPost();
        PostBuilder::create()-&gt;setTitle('Post two')-&gt;getPost();

        $this-&gt;createNode([
          'title' =&gt; 'This is not a post',
          'type' =&gt; 'page',
        ]);

        $this-&gt;drupalGet('/blog');

        $assert = $this-&gt;assertSession();
        $assert-&gt;pageTextContains('Post one');
        $assert-&gt;pageTextContains('Post two');
        $assert-&gt;pageTextNotContains('This is not a post');
      }
      </code></pre>

      <p>Now the test passes.</p>

      <p>Doing test-driven development keeps my code clean and minimal, and I find this approach keeps my test clean, too.</p>

              
    format: full_html
    processed: |
      <p>As well as <a href="http://default/daily/2024/06/03/writing-comments-first">writing comments first</a>, when writing tests, I sometimes like to write my tests backwards and start by writing the assertions first.</p>

      <p>I know what I want to assert in the test, so it's an easy place to start.</p>

      <p>I'll run it, see the error, fix it and continue working backwards.</p>

      <p>For example, I could start with this:</p>

      <pre><code class="php">public function testOnlyPostNodesAreShown(): void {
        $assert = $this-&gt;assertSession();
        $assert-&gt;pageTextContains('Post one');
        $assert-&gt;pageTextContains('Post two');
        $assert-&gt;pageTextNotContains('This is not a post');
      }
      </code></pre>

      <p>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.</p>

      <p>In this case, I need to make a request to the page that should render the text:</p>

      <pre><code class="php">public function testOnlyPostNodesAreShown(): void {
        $this-&gt;drupalGet('/blog');

        $assert = $this-&gt;assertSession();
        $assert-&gt;pageTextContains('Post one');
        $assert-&gt;pageTextContains('Post two');
        $assert-&gt;pageTextNotContains('This is not a post');
      }
      </code></pre>

      <p>This will still fail, as I also need to create the required posts:</p>

      <pre><code class="php">public function testOnlyPostNodesAreShown(): void {
        PostBuilder::create()-&gt;setTitle('Post one')-&gt;getPost();
        PostBuilder::create()-&gt;setTitle('Post two')-&gt;getPost();

        $this-&gt;createNode([
          'title' =&gt; 'This is not a post',
          'type' =&gt; 'page',
        ]);

        $this-&gt;drupalGet('/blog');

        $assert = $this-&gt;assertSession();
        $assert-&gt;pageTextContains('Post one');
        $assert-&gt;pageTextContains('Post two');
        $assert-&gt;pageTextNotContains('This is not a post');
      }
      </code></pre>

      <p>Now the test passes.</p>

      <p>Doing test-driven development keeps my code clean and minimal, and I find this approach keeps my test clean, too.</p>

              
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