code: function createApi () {
    api = {
      eth: {
        blockNumber: sinon.stub().resolves(new BigNumber(2)),
        gasPrice: sinon.stub().resolves(GASPRICE)
      },
      parity: {
        gasPriceHistogram: sinon.stub().resolves(HISTOGRAM)
      }
    };
  
    return api;
  }
docs: TODO: share with gasPriceEditor.spec.js