function assertHasCssClass(container, cssName) {
  var page = container.children[0];
  assertTrue(goog.dom.classlist.contains(page,  goog.getCssName(cssName)));
}
@param {!Element} container The container element to check.
@param {string} cssName The css class name to check for.
Asserts the element provided has a child with the provided css name.