function assertColoursAndTitles(field, expectedColours, expectedTitles) {
        const options = field.getOptions();
        const actualColours = options.map((option) =>
          Blockly.utils.colour.parse(option[0].style.backgroundColor),
        );
        const actualTitles = options
          .map((option) => option[0].title)
          .filter((title) => !!title);
        assert.equal(String(actualColours), String(expectedColours));
        assert.equal(String(actualTitles), String(expectedTitles));
      }
Verify that the list of colours and titles are as expected.
@param {!FieldColour} field Field to test.
@param {!Array[string]} expectedColours Array of colour names.
@param {!Array[string]} expectedTitles Array of title names.