react-native-ultimate-config/src/load-env.spec.js

Config that works

const mockReadFileSync = jest.fn();
jest.doMock("fs", () => ({ readFileSync: mockReadFileSync }));
const mockConfig = jest.fn();
jest.doMock("dotenv", () => ({ config: mockConfig }));
const mockYaml = jest.fn();
jest.doMock("js-yaml", () => ({ load: mockYaml }));
const load_env = require("./load-env");

describe("load-env", () => {
  beforeEach(() => {
    mockConfig.mockReset();
    mockYaml.mockReset();
    mockReadFileSync.mockReset();
  });
  it("reads dotenv by default", () => {
    mockConfig.mockReturnValueOnce({ parsed: { hello: "world" } });
    const result = load_env("hello");
    expect(mockConfig).toHaveBeenCalledWith({ path: "hello" });
    expect(result).toEqual({ hello: "world" });
  });
  it.each`
    extension
    ${"yml"}
    ${"yaml"}
  `("reads yaml when extension is '$extension'", ({ extension }) => {
    mockReadFileSync.mockReturnValueOnce(Buffer.from("data"));
    mockYaml.mockReturnValueOnce({ hello: "world" });
    const result = load_env(`hello.${extension}`);
    expect(mockReadFileSync).toHaveBeenCalledWith(`hello.${extension}`);
    expect(mockYaml).toHaveBeenCalledWith("data");
    expect(result).toEqual({ hello: "world" });
  });
  describe.each`
    extension
    ${"yml"}
    ${"yaml"}
  `(
    "throw when yaml is not an object with extension '$extension'",
    ({ extension }) => {
      it.each`
        content
        ${"abc:def"}
        ${false}
        ${true}
        ${42}
        ${null}
        ${undefined}
      `("when content is '$content'", ({ content }) => {
        mockReadFileSync.mockReturnValueOnce(Buffer.from("data"));
        mockYaml.mockReturnValueOnce(content);
        expect(() => {
          load_env(`hello.${extension}`);
        }).toThrow();
      });
    }
  );
});