Reworked the scoped styles acceptance test to stop comparing the entire text-decoration shorthand (which can vary across browsers) and instead assert the specific textDecorationLine and textDecorationColor values using getComputedStyle.

Added explicit existence checks before reading computed styles so the test fails loudly if expected elements go missing.
Adjusted the negative expectation to ensure the non-addon component isn’t styled with underline rgb(0, 0, 0).
With these changes the test now captures the intent (“underline in black”) while avoiding brittle string comparisons.

Author: habdelra

test-app/tests/acceptance/scoped-css-test.ts

@@ -130,19 +130,45 @@ module('Acceptance | scoped css', function (hooks) {
   test('an addon can use scoped styles', async function (assert) {
     await visit('/');
 
-    assert.dom('[data-scoped-underline-addon-component]').hasStyle({
-      textDecoration: 'underline solid rgb(0, 0, 0)',
-    });
+    let underlineComponent = find('[data-scoped-underline-addon-component]');
+    if (!underlineComponent) {
+      throw new Error(
+        '[data-scoped-underline-addon-component] element not found'
+      );
+    }
+    let underlineComponentStyles = getComputedStyle(underlineComponent);
+    assert.strictEqual(
+      underlineComponentStyles.textDecorationLine,
+      'underline'
+    );
+    assert.strictEqual(
+      underlineComponentStyles.textDecorationColor,
+      'rgb(0, 0, 0)'
+    );
 
     assert
       .dom('[data-test-underline-component-outside-addon]')
       .doesNotHaveStyle({
-        textDecoration: 'underline solid rgb(0, 0, 0)',
+        textDecoration: 'underline rgb(0, 0, 0)',
       });
 
-    assert.dom('[data-test-paragraph-with-class-styled-by-addon]').hasStyle({
-      textDecoration: 'underline solid rgb(0, 0, 0)',
-    });
+    let classStyledParagraph = find(
+      '[data-test-paragraph-with-class-styled-by-addon]'
+    );
+    if (!classStyledParagraph) {
+      throw new Error(
+        '[data-test-paragraph-with-class-styled-by-addon] element not found'
+      );
+    }
+    let classStyledParagraphStyles = getComputedStyle(classStyledParagraph);
+    assert.strictEqual(
+      classStyledParagraphStyles.textDecorationLine,
+      'underline'
+    );
+    assert.strictEqual(
+      classStyledParagraphStyles.textDecorationColor,
+      'rgb(0, 0, 0)'
+    );
   });
 
   test('unscoped styles can use interpolation', async function (assert) {