eslint-plugin-jest/lib/rules/prefer-spy-on.js

Eslint rules for Jest

'use strict';

function _slicedToArray(arr, i) { return _arrayWithHoles(arr) || _iterableToArrayLimit(arr, i) || _nonIterableRest(); }

function _nonIterableRest() { throw new TypeError("Invalid attempt to destructure non-iterable instance"); }

function _iterableToArrayLimit(arr, i) { var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

function _arrayWithHoles(arr) { if (Array.isArray(arr)) return arr; }

const _require = require('./util'),
      getDocsUrl = _require.getDocsUrl,
      getNodeName = _require.getNodeName;

const getJestFnCall = node => {
  if (node.type !== 'CallExpression' && node.type !== 'MemberExpression' || node.callee && node.callee.type !== 'MemberExpression') {
    return null;
  }

  const obj = node.callee ? node.callee.object : node.object;

  if (obj.type === 'Identifier') {
    return node.type === 'CallExpression' && getNodeName(node.callee) === 'jest.fn' ? node : null;
  }

  return getJestFnCall(obj);
};

module.exports = {
  meta: {
    docs: {
      url: getDocsUrl(__filename)
    },
    messages: {
      useJestSpyOn: 'Use jest.spyOn() instead.'
    },
    fixable: 'code'
  },

  create(context) {
    return {
      AssignmentExpression(node) {
        if (node.left.type !== 'MemberExpression') return;
        const jestFnCall = getJestFnCall(node.right);
        if (!jestFnCall) return;
        context.report({
          node,
          messageId: 'useJestSpyOn',

          fix(fixer) {
            const leftPropQuote = node.left.property.type === 'Identifier' ? "'" : '';

            const _jestFnCall$arguments = _slicedToArray(jestFnCall.arguments, 1),
                  arg = _jestFnCall$arguments[0];

            const argSource = arg && context.getSourceCode().getText(arg);
            const mockImplementation = argSource ? `.mockImplementation(${argSource})` : '';
            return [fixer.insertTextBefore(node.left, `jest.spyOn(`), fixer.replaceTextRange([node.left.object.range[1], node.left.property.range[0]], `, ${leftPropQuote}`), fixer.replaceTextRange([node.left.property.range[1], jestFnCall.range[1]], `${leftPropQuote})${mockImplementation}`)];
          }

        });
      }

    };
  }

};