discourse/app/assets/stylesheets/qunit-custom.scss

#ember-testing-container {
  position: fixed;
  background: #fff;
  bottom: 0;
  right: 0;
  width: 640px;
  height: 384px;
  overflow: auto;
  z-index: 9999;
  border: 1px solid #ccc;
  transform: translateZ(0);
  box-sizing: border-box;
  max-height: 100vh;
}

#ember-testing {
  background-color: #fff;
}

.discourse-root {
  background: var(--secondary);
}

#ember-testing {
  width: 200%;
  height: 200%;
  transform: scale(0.5);
  transform-origin: top left;
}

@media (prefers-color-scheme: dark) {
  html {
    background-color: #222;
  }

  #qunit-banner.qunit-pass {
    background-color: #92b01e;
  }

  #qunit-banner.qunit-fail {
    background-color: #7e2121;
  }

  #qunit-testrunner-toolbar {
    background: #1b1b1b;
    color: #90ac2d;
  }

  #qunit-testrunner-toolbar button {
    background-color: #222;
    border-color: #444;
    color: #f8f8f8;
  }

  #qunit-filter-input,
  #qunit-urlconfig-qunit_single_plugin {
    background-color: var(--primary);
    border: 1px solid var(--secondary-medium);
    color: var(--secondary);
  }

  #qunit-filteredTest {
    background-color: #90ac2d;
    color: #366097;
  }

  #qunit-testresult {
    background-color: #366097;
    border-color: #000;
    color: #e2f0f7;
  }

  #qunit-testresult a {
    color: #7eb0f2;
  }

  #qunit-tests b.counts {
    color: #ddd;
  }

  #qunit-tests b.failed {
    color: #ff7777;
  }

  #qunit-tests b.passed {
    color: #90ac2d;
  }

  #qunit-tests .pass {
    background-color: #0c3f59;
    border-color: #000;
    color: #edeff5;
  }

  #qunit-tests .pass .test-name {
    color: #7eb0f2;
  }

  #qunit-tests .fail {
    background-color: #7e2121;
    color: #ddd;
  }

  ol.qunit-assert-list > li > table > tbody,
  tr.test-expected,
  tr.test-actual,
  tr.test-source {
    border-color: #333;
  }

  #qunit-tests li {
    border-color: #333;
  }

  #qunit-tests li li.pass {
    background-color: #222;
    border-color: #92b01e;
    color: #90ac2d;
  }

  #qunit-tests li li.fail {
    background-color: #222;
    border-color: #7e2121;
    color: #ff7777;
  }

  .qunit-assert-list {
    background-color: #222;
  }

  #ember-testing-container {
    background-color: #000;
    border-color: #444;
  }

  #ember-testing {
    background: #000;
  }
}