CODEWITHSUNDEEP
javascriptnode.jsunit-testingtypescriptjestjs
ConstantineK
ConstantineK

Reputation: 362

Testing Typescript with Jest, how do I test an internal function? My import/export is failing me

I am new to Typescript and wanted to implement unit testing with Jest. I installed Jest, and when I run it I receive an error, I have simplified the code for this example, and it continues to fail:

FAIL  src\__tests__\validateSender.ts 
https validation
ReferenceError: validateSender is not defined

  at Object.<anonymous>.test (src/__tests__/validateSender.ts:10:10)
  at process._tickCallback (internal/process/next_tick.js:109:7)

The test which cannot find the function (./src/__tests__/validateSender.js):

import {} from "jest";
const connection = {
  encrypted: "undefined",
};
const req = {
  connection : ("{connection}"),
};

test("https validation", () => {
  expect(validateSender(req)).toThrow();
});

the function (./src/validateSender.js):

function validateSender(req) {
  if (typeof req.connection.encrypted === "undefined") {
    throw new CustomException("validateSender", "connection must be secured.");
  } else { return; }
}

my Jest package.json portion (./package.json):

"jest": {
    "transform": {
      "^.+\\.tsx?$": "<rootDir>/node_modules/ts-jest/preprocessor.js"
    },
    "testRegex": "(/__tests__/.*|(\\.|/)(test|spec))\\.(jsx?|tsx?)$",
    "moduleFileExtensions": [
      "ts",
      "tsx",
      "js",
      "jsx",
      "json"
    ]
  }

I have attempted adding an import statement for the validateSender file directly, but it fails in the same way (on npm test from the root directory I added import {} from "./src/validateSender"; to the file and received the error above.)

It was also suggested I try import validateSender from "./src/validateSender"; but I receive error TS2307: Cannot find module './src/validateSender'.

It appears that I am missing some foundational knowledge for this process, but I have failed to find it in the TS handbook.

Upvotes: 1

Views: 3696

Answers (1)

Fenton
Fenton

Reputation: 251222

In order to test a module member, it must be exported. Otherwise it isn't visible to your test.

This doesn't mean you need to export everything - you can test at your public API in most cases and cover the internal members.

Module File

export function validateSender(req) {
    if (typeof req.connection.encrypted === "undefined") {
        throw new Error("validateSender connection must be secured.");
    } else { return; }
}

Test File

import "jest";
import { validateSender } from './ext';

const connection = {
  encrypted: "undefined",
};
const req = {
  connection: ("{connection}"),
};

test("https validation", () => {
  expect(validateSender(req)).toThrow();
});

This will get you this far:

Test Result

And finally... to expect something to throw, you'll need to adjust your code to:

test("https validation", () => {
  expect(() => validateSender(req)).toThrow();
});

This passes an un-executed function that will be executed within the test, rather than executing the function and passing the result.

enter image description here

Upvotes: 1

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