bug: Test Function toEqualHtml does not work with disabled shadowdom and slots properly

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
42/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
typescript
Domain
testing, web-dev

Research direction

Reproduce the failure in src/components/test-with-slot/test/test-with-slot.spec.tsx using newSpecPage and toEqualHtml, then trace how the slot output is represented during comparison. Done means a component with shadow:false and a slot can be compared with toEqualHtml without the unexpected comment causing failure, with the documented behavior covered.

Written by the indexing model from the issue text.

Description

Bug: Validated
Prerequisites
Stencil Version

2.7.0

Current Behavior

Using a slot should not compromise a component's testability.
Currently using a slot (with shadow:false) causes unit tests to fail due to a HTML comment being inserted as it seems.
Removing the slot "fixes" the testcase (but makes it useless).

Expected Behavior

a) It is possible to use toEqualHtml to test a component with a slot and get proper error messages when test cases fail
b) it is documented

Steps to Reproduce

Following testcase should work (toEqualHtml should normalize whitespaces anyway, adding or removing whitespaces to expectation does not change result).

@Component({
  tag: 'test-with-slot',
  styleUrl: 'test-with-slot.css',
  shadow: false,
})
export class TestWithSlot {
  render() {
    return (
      <Host>
        <slot></slot>
      </Host>
    );
  }


  /* OUTPUT:
      - <test-with-slot></test-with-slot>
      + <test-with-slot>
      + </test-with-slot>
  */
  it('should work as expected', async () => {
    const page = await newSpecPage({
      components: [TestWithSlot],
      html: `<test-with-slot></test-with-slot>`,
    });
    expect(page.root).toEqualHtml(`
      <test-with-slot>
      </test-with-slot>
    `);
  });
Code Reproduction URL

https://github.com/raspyweather/stencil-issues/blob/master/src/components/test-with-slot/test/test-with-slot.spec.tsx

Additional Information

Comparing "manually" via outerHTML reveals what looks like a HTML comment being inserted by the framework which causes the comparison to fail.
I suspect the issue described above being not visible due to "prettyprinting" HTML to the console which I suspect hides the HTML comment and therefore makes it look like the issue would be caused by whitespaces.


  /* OUTPUT
    - <test-with-slot></test-with-slot>
    + <test-with-slot>
    +   <!---->
    + </test-with-slot>
  */
  it('should work with manual comparison - fails', async () => {
    const page = await newSpecPage({
      components: [TestWithSlot],
      html: `<test-with-slot></test-with-slot>`,
    });
    expect(page.root.outerHTML).toEqualHtml(`
      <test-with-slot>
      </test-with-slot>
    `);
  });
Dominant language
TypeScript
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Merged PRs (30d)
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