This is a testharness.js-based test.
[FAIL] contenteditable=plaintext-only in the design mode should not prevent the style edit
  assert_equals: expected "<div contenteditable=\\"plaintext-only\\"><b>ABC</b></div>" but got "<div contenteditable=\\"plaintext-only\\">ABC</div>"
[FAIL] contenteditable=plaintext-only in the design mode should not cause inserting line break at typing Enter
  assert_equals: expected "<div contenteditable=\\"plaintext-only\\"><p>A</p><p>B</p></div>" but got "<div contenteditable=\\"plaintext-only\\"><p>\\nAB</p></div>"
Harness: the test ran to completion.