NestJS GraphQL E2E Plugin Example

NestJS comes with a great plugin for working with GraphQL so that you don't have to decorate each and every property with @Field(). This makes development much easier, but it bring a challenge to testing. As Nest advocates for using Jest (and there's nothing wrong with that) to use Jest with Typescript we need to use the ts-jest package. The problem here is that ts-jest uses Typescript's compiler when it comes to transforming the ts files into js files. Nest uses Typescript's compiler as well, but with a couple of tweaks to it to work with the auto generation of GraphQL models that are properly decorated.

The Problem

Running E2E tests is now an issue using the NestJS GraphQL CLI PLugin because the models are no longer decorated with the proper values for the GraphQLModule to function as expected.

The Solution

Instead of using ts-jest for E2E tests, it helps to build a script to compile all of your ts files (yes, spec files included) and turn them into js files so that jest can run the test files directly. The best way to go about this is to create a specific tsconfig file for your E2E tests, and a pretest:e2e script that does the build when you run the test:e2e script in the package.json. The tsconfig could look something like this:

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "outDir": "dist-test"
  },
  "include": ["src", "test"]
}

and the pretest:e2e script could be something like this

"pretest:e2e": "nest build -p tsconfig.test.json && cp ./test/jest-e2e.json ./dist-test/test/",
"test:e2e": "jest --config ./dist-test/test/jest-e2e.json"

Make sure to also update the test/jest-e2e.json to no longer reference any ts files, or make use of `ts-jest

{
  "moduleFileExtensions": ["js", "json", "ts"],
  "rootDir": ".",
  "testEnvironment": "node",
  "testRegex": ".e2e-spec.js$"
}

And now you should be able to run <pkg manager run> test:e2e and have a full test execution of your E2E tests, including Nest building the models for GraphQL.

Enjoy!