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CodeSOD: Module Test

The Daily WTF
3 days 10 hours ago

TJ inherited a NestJS project. The original developers left the team many years ago, but they've left their mark in the codebase.

// ProjectsModule.ts @Module({ controllers: […], providers: […], exports: […], }) export class ProjectsModule {}

NestJS is a dependency-injection oriented framework for TypeScript code. It offers "providers" (dependencies that can be injected), "controllers" (as one would expect), and lets you bundle them together into "modules". Modules can depend on other modules, letting you build a modular and flexible graph of dependencies. This means that the empty module isn't wrong here.

No, for it to be wrong, we need to write some tests:

// ProjectsModule.test.ts describe("ProjectsModule", () => { it("can be created", () => { const projectsModule = new ProjectsModule() expect(projectsModule).toBeTruthy() }) })

Since modules are just containers for related code objects, there isn't much to test here. While "dynamic modules" which execute code are a thing, they don't execute that code at construction time anyway. This test will always pass. It isn't a test, it doesn't do anything. It likely doesn't even get their coverage up, since whatever providers or controllers it's referencing aren't covered by this test. It's a test that tests nothing but the framework it runs on top of.

"At least there are tests," TJ writes.

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Remy Porter