This might be a hoisting issue. If you have more JS code above your code snippet, test might have been assigned to something else.

This will cause a TypeError because test will be a string by the time you call it:

// ... some code

var test = 'This is a test.';

// ... more code

function test() {
  console.log(this);
}

test();

This will work because test is assigned to a function right before you call it:

// ... some code

var test = 'This is a test.';

// ... more code

test = function () {
  console.log(this);
}

test();

In the first example, this is what the interpreter does, more or less:

1. Assign a function definition to test. (This happens first because it hoists function declarations above everything else)
2. Reassign test to be a string.
3. Invoke test, which is a string.

Second example:

1. Declare test with no value (undefined).
2. Assign test to a string.
3. Reassign test to a function.
4. Invoke test, which is a function.

Just found out that my test code had wrong brackets placement: it was

contract("Marketplace"), accounts => {
  //all tests go inside here

  let marketplace;
  before(async () => {
    marketplace = await Marketplace.deployed();
  });

  //describe comes from Mocha framework
  describe("deployment", async () => {
    it("deploys successfully", async () => {
      const address = await marketplace.address;
      assert.notEqual(address, 0x0);
      assert.notEqual(address, "");
      assert.notEqual(address, null);
      assert.notEqual(address, undefined);
    });

it should be

contract("Marketplace", accounts => {
  //all tests go inside here

  let marketplace;
  before(async () => {
    marketplace = await Marketplace.deployed(); //this will get the deployed copy of the contract
  });

  //describe comes from Mocha framework
  describe("deployment", async () => {
    it("deploys successfully", async () => {
      const address = await marketplace.address;
      assert.notEqual(address, 0x0);
      assert.notEqual(address, "");
      assert.notEqual(address, null);
      assert.notEqual(address, undefined);
    });

notice the bracket after"marketplace" changes everything, the compiler won't complain since in the end of the file I had an extra bracket.

In my case, I had to mock a Node.js module. I'm using React and Redux in ES6, with Jest and Enzyme for unit tests.

In the file I'm using, and writing a test for, I'm importing the node modules as default:

import nodeModulePackage from 'nodeModulePackage';

So I needed to mock it as a default since I kept getting the error (0, _blah.default) is not a function..

My solution was to do:

jest.mock('nodeModulePackage', () => jest.fn(() => {}));

In my case, I just needed to override the function and make it return an empty object.

If you need to call a function on that node module, you'll do the following:

jest.mock('nodeModulePackage', () => ({ doSomething: jest.fn(() => 'foo') }));

Your pattern must be RegEx literal (double quotes around that should not be there) like this

var pattern = /^(()?\d{3}())?(-|\s)?\d{3}(-|\s)?\d{4}$/;

Otherwise you need to use RegExp object, with proper escaping for \, like this

var pattern = new RegExp("^(()?\\d{3}())?(-|\\s)?\\d{3}(-|\\s)?\\d{4}$");

class MockPartservice {

    list():Obserable<Part>{
      let part1:Part;
      part1=new Part();
      part1.description="This is a test data";
      part1.name="Hello";
      part1.uuid="ABCD1234";
      return of(part1);
    }

};

You need to return a Observable and return data using of() operator.And both need to be import from 'rxjs'

and you don't need to use spyOn

Try moving your parens around to something like...

expect(validateEmail('[email protected]')).toBe(true);

or something like this for the second test

expect(validateEmail('badEmail')).toBe(false);

It looks like the reason why you're getting this error has to do with the data you're mocking through Jest.

Try using jest.fn() to mock your getIdToken as a function, rather than a string:

const mockGetIdToken = jest.fn(() => 'abc123');

jest.mock('services/firebase', () => new Promise(resolve => resolve({
  signInWithEmailAndPassword: () => Promise.resolve({ getIdToken: mockGetIdToken }),
  getIdToken: mockGetIdToken,
  signOut: () => jest.fn()
})));

describe('login actions', () => {
  let store;

  beforeEach(() => {
    store = mockStore({});
  });

  it('signIn should call firebase', () => {
    const user = {
      email: '[email protected]',
      password: 'abd123'
    };

    return store.dispatch(signIn(user.email, user.password))
      .then(() => {
        console.log('TEST signIn SUCCESS');
        expect(mockSignIn).toHaveBeenCalled();
        expect(store.getActions()).toEqual({
          type: USER_ON_LOGGED_IN
        });
      })
      .catch((err) => {
        console.log('TEST signIn ERROR =>', err);
      });
  });

As you are running your project with typescript, your test files should be in .ts too (maybe you'll need to adjust jest config to make it run properly).

Try to export the x function this way in x.ts:

export const x = (a: number, b: number) => {
  return a + b
}

Change test.spec.js to test.spec.ts and import x this way:

import { x } from '../functions/x'