This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript. code example

Example 1: Error: It looks like you are passing several store enhancers to createStore(). This is not supported. Instead, compose them together to a single function.

import { createStore, compose, applyMiddleware } from 'redux';
import thunk from 'redux-thunk';
import reducers from '../reducers';

const composeEnhancer = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ || compose;

const store = createStore(
  reducers,
  composeEnhancer(applyMiddleware(thunk)),
);

export default store;

Example 2: There might be a problem with the project dependency tree. It is likely not a bug in Create React App, but something you need to fix locally.

/* Answer to: "There might be a problem with the project dependency tree. It is likely not a bug in Create React App, but something you need to fix locally." */

/*
  Go to your "package.json" file.
  Replace
*/
  "react-scripts": "<whatever-is-currently-here>",
/* with */
  "react-scripts": "1.1.4",
/*
  Then run npm install and after that npm start
*/

Example 3: python Cannot uninstall 'PyYAML'. It is a distutils installed project and thus we cannot accurately determine which files belong t o it which would lead to only a partial uninstall when trying to install chatterbot or chatterbot_corpus

pip install chatterbot-corpus --ignore-installed

Example 4: Expected a state variable declaration. If you intended this as a fallback function or a function to handle plain ether transactions, use the "fallback" keyword or the "receive" keyword instead.

pragma solidity >=0.4.22 <0.6.0;

contract OwnedToken {
    // `TokenCreator` is a contract type that is defined below.
    // It is fine to reference it as long as it is not used
    // to create a new contract.
    TokenCreator creator;
    address owner;
    bytes32 name;

    // This is the constructor which registers the
    // creator and the assigned name.
    constructor(bytes32 _name) public {
        // State variables are accessed via their name
        // and not via e.g. `this.owner`. Functions can
        // be accessed directly or through `this.f`,
        // but the latter provides an external view
        // to the function. Especially in the constructor,
        // you should not access functions externally,
        // because the function does not exist yet.
        // See the next section for details.
        owner = msg.sender;

        // We do an explicit type conversion from `address`
        // to `TokenCreator` and assume that the type of
        // the calling contract is `TokenCreator`, there is
        // no real way to check that.
        creator = TokenCreator(msg.sender);
        name = _name;
    }

    function changeName(bytes32 newName) public {
        // Only the creator can alter the name --
        // the comparison is possible since contracts
        // are explicitly convertible to addresses.
        if (msg.sender == address(creator))
            name = newName;
    }

    function transfer(address newOwner) public {
        // Only the current owner can transfer the token.
        if (msg.sender != owner) return;

        // We ask the creator contract if the transfer
        // should proceed by using a function of the
        // `TokenCreator` contract defined below. If
        // the call fails (e.g. due to out-of-gas),
        // the execution also fails here.
        if (creator.isTokenTransferOK(owner, newOwner))
            owner = newOwner;
    }
}

contract TokenCreator {
    function createToken(bytes32 name)
       public
       returns (OwnedToken tokenAddress)
    {
        // Create a new `Token` contract and return its address.
        // From the JavaScript side, the return type is
        // `address`, as this is the closest type available in
        // the ABI.
        return new OwnedToken(name);
    }

    function changeName(OwnedToken tokenAddress, bytes32 name) public {
        // Again, the external type of `tokenAddress` is
        // simply `address`.
        tokenAddress.changeName(name);
    }

    // Perform checks to determine if transferring a token to the
    // `OwnedToken` contract should proceed
    function isTokenTransferOK(address currentOwner, address newOwner)
        public
        pure
        returns (bool ok)
    {
        // Check an arbitrary condition to see if transfer should proceed
        return keccak256(abi.encodePacked(currentOwner, newOwner))[0] == 0x7f;
    }
}