grafana/public/app/plugins/panel/nodeGraph/layout.test.ts

import { renderHook } from '@testing-library/react';

import { useLayout } from './layout';
import { EdgeDatum, NodeDatum } from './types';

let onmessage: jest.Mock;
let postMessage: jest.Mock;
let terminate: jest.Mock;

jest.mock('./createLayoutWorker', () => {
  return {
    __esModule: true,
    createWorker: () => {
      onmessage = jest.fn();
      postMessage = jest.fn();
      terminate = jest.fn();
      return {
        onmessage: onmessage,
        postMessage: postMessage,
        terminate: terminate,
      };
    },
  };
});

describe('layout', () => {
  it('doesnt fail without any data', async () => {
    const nodes: NodeDatum[] = [];
    const edges: EdgeDatum[] = [];

    const { result } = renderHook(() => {
      return useLayout(nodes, edges, undefined, 100, 1000);
    });
    expect(result.current.nodes).toEqual([]);
    expect(result.current.edges).toEqual([]);
    expect(postMessage).toBeUndefined();
  });

  it('cancels worker', async () => {
    const { result, rerender } = renderHook(
      ({ nodes, edges }) => {
        return useLayout(nodes, edges, undefined, 100, 1000);
      },
      {
        initialProps: {
          nodes: [makeNode(0, 0), makeNode(1, 1)],
          edges: [makeEdge(0, 1)],
        },
      }
    );
    expect(postMessage).toBeCalledTimes(1);
    // Bit convoluted but we cannot easily access the worker instance as we only export constructor so the default
    // export is class and we only store latest instance of the methods as jest.fn here as module local variables.
    // So we capture the terminate function from current worker so that when we call rerender and new worker is created
    // we can still access and check the method from the old one that we assume should be canceled.
    const localTerminate = terminate;

    rerender({
      nodes: [],
      edges: [],
    });

    expect(result.current.nodes).toEqual([]);
    expect(result.current.edges).toEqual([]);
    expect(localTerminate).toBeCalledTimes(1);
  });
});

function makeNode(index: number, incoming: number): NodeDatum {
  return {
    id: `n${index}`,
    title: `n${index}`,
    subTitle: '',
    dataFrameRowIndex: 0,
    incoming,
    arcSections: [],
  };
}

function makeEdge(source: number, target: number): EdgeDatum {
  return {
    id: `${source}-${target}`,
    source: 'n' + source,
    target: 'n' + target,
    mainStat: '',
    secondaryStat: '',
    dataFrameRowIndex: 0,
  };
}