Jest mock mockReturnValue not a function

Question

Hi I am trying to mock a function from a module within my node_modules. The current way I have tried is

import { getPriceImpactForPosition } from "@gmx-io/sdk/utils/fees/priceImpact.js";
import { getBasisPoints } from "@gmx-io/sdk/utils/numbers.js";

// Move these mocks before any imports
jest.mock("@gmx-io/sdk/utils/fees/priceImpact.js", () => ({
  getPriceImpactForPosition: jest.fn()
}));

jest.mock("@gmx-io/sdk/utils/numbers.js", () => ({
  getBasisPoints: jest.fn()
}));

but when I call .mockReturnValue on the mock it says it is not a function. I assume that it is not being mocked properly, and is still calling the actual implementation.

Below is my jest.config.js file

/** @type {import('ts-jest').JestConfigWithTsJest} **/
export default {
  preset: "ts-jest/presets/js-with-ts-esm",
  testEnvironment: "node",
  testPathIgnorePatterns: ["/node_modules/", "/dist/"],
  transformIgnorePatterns: ["node_modules/(?!(@gmx-io/sdk))"],
  extensionsToTreatAsEsm: [".ts", ".jsx"],
  transform: {
    "^.+\\.(ts|js|mjs)$": ["ts-jest", {
      useESM: true,
      tsconfig: "tsconfig.json",
    }],
  },
  moduleNameMapper: {
    "^(\\.{1,2}/.*)\\.js$": "$1"
  }
};

I had a look into the package as well to find the functions that I am trying to mock, it seems that the module itself is using package exports and I am not sure if this will affect mocking in anyway

  "exports": {
    ".": {
      "import": "./build/src/index.js",
      "require": "./build/src/index.js"
    },
    "./abis/*": "./build/abis/*",
    "./prebuilt/*": "./build/prebuilt/*",
    "./utils/*": "./build/src/utils/*",
    "./types/*": "./build/src/types/*",
    "./configs/*": "./build/src/configs/*"
  },

This is currently how I am running my tests

NODE_OPTIONS=--experimental-vm-modules jest --passWithNoTests

Answer 1

Use jest.unstable_mockModule() instead of jest.mock() for ESM compatibility.
Ensure mocks are set up before importing the module using await import().