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Running jest test with coverage in typescript create-react-app (v2.1) throws super constructor error

See original GitHub issue

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Jest, test, coverage, extends


npm create-react-app --info actually throws an error (tried on 2 clean installs on Windows 10, 64bit latest version of node). I have reproduced on 2.1.1 of create-react-app.

Error when running npx create-react-app --info :

Environment Info:
(node:9568) UnhandledPromiseRejectionWarning: Error: The system cannot find the path specified.

Steps to Reproduce

Create a new react app with typescript support (create-react-app v2.1 or higher required):

npx create-create-app jest-test --typescript

Add a new test file named “classes.tsx” to the src/ folder containing this code:

class Base {
  public counter: number = 0;
  increment() {

class Derived extends Base {
  constructor(public anotherCount: number) {

export { Base, Derived };

Edit the existing src/App.test.tsx file, adding this import:

import { Base, Derived } from "./classes";

… and this extra test:

it('coverage trigger', () => {
  const derivedInstance = new Derived(1);

Edit package.json and add a new script below “scripts” to run tests with coverage:

"test:coverage": "react-scripts test --coverage"

From a command line in the project directory, run npm run test:coverage

Expected Behavior

The tests should complete without error with the --coverage option enabled.

Actual Behavior

The following error appears:

ReferenceError: Must call super constructor in derived class before accessing 'this' or returning from derived constructor

       8 | class Derived extends Base {
    >  9 |   constructor(public anotherCount: number) {
         |                                            ^
      10 |     super();
      11 |   }

Note that running the tests without the --coverage option works fine.

Reproducible Demo

From a command line in the project directory, run npm run test:coverage

Issue Analytics

  • State:closed
  • Created 5 years ago
  • Reactions:2
  • Comments:7 (3 by maintainers)

github_iconTop GitHub Comments

SimenBcommented, Jul 4, 2019
SimenBcommented, Jun 19, 2019

You’re waiting for Babel 7.5.0 release, which will include

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