testdouble-component

Extends testdouble with a component function -- with the hopes that creating test doubles for React components is slightly more approachable.

import td from "testdouble";
import { setup } from "@bvarberg/testdouble-component";

// Augment testdouble with td.component
setup(td);

// It is likely you'll want to use `td.config` to ignore warnings about stubbing
// and verifying on the same test double
td.config({
  ignoreWarnings: true
});

td.component

Under the hood, td.component creates a double using td.function.

It sets up a catch-all stubbing that returns a JSX fragment instead of undefined, and sets a displayName to improve debugging/console/test runner output.

---

One way to use td.component, using Jest for module replacement.

describe("Consumer", () => {
  beforeEach(() => {
    jest.dontMock("./Consumer");
    jest.doMock("./Collaborator", () => ({
      // Create a test double for a function component
      Collaborator: td.component("Collaborator"),
    }));
  });

  test("renders the collaborator with some specific props", async () => {
    const { Collaborator } = await import("./Collaborator");
    const { Consumer } = await import("./Consumer");

    render(<Consumer />); // which renders <Collaborator ... />

    td.verify(Collaborator({ someProp: 'expected' }), { ignoreExtraArgs: true }); // ignore the second context argument
  });
});

When used with Jest + dynamic imports in this way, Collaborator will be typed based on the real component exported from the module.