How can I configure tsc to compile test specs from a specific folder?

I'm implementing e2e tests into an Angular project. It wasn't started with @angular-cli, so I'm configuring most of it manually.

What I'm trying to do now is to define a script in package.json to transpile only the specs in tests/ folder to tests/compiled.

I tried to follow this question: tsconfig.json - Only build ts files from folder. It recommends to use --rootDir to define the folder.

But if I use this: tsc --rootDir tests --outDir ./tests/compiled, it compiles files from other folders anyways (like ./src). Also, it returns a lot of TS6059 errors, complaining that rootDir should contain all source files.

An example: error TS6059: File 'C:/Users/Betalabs/Documents/Projetos/Engine-Frontend/src/vendor.browser.ts' is not under 'rootDir' 'tests'. 'rootDir' is expected to contain all source files.

The file hierarchy is this. Please note that the test specs (*.spec.ts) I want to transpile are in the tests/ folder.

(root) -- src/ -- tests/ -- compiled/ -- (transpiled test files, ".js") -- helpers/ -- (helper modules, ".ts") -- page-objects/ -- (page objects, ".ts") -- forms.spec.ts -- filters.spec.ts -- .gitignore -- .tern-project -- buildspec.yml -- conf.js -- package-lock.json -- package.json -- README.md -- tsconfig.json -- tsconfig.webpack.json -- tslint.json -- typedoc.json -- webpack.config.js 

This is my tsconfig.json:

{ "compilerOptions": { "target": "es5", "module": "commonjs", "moduleResolution": "node", "emitDecoratorMetadata": true, "experimentalDecorators": true, "allowSyntheticDefaultImports": true, "sourceMap": true, "noEmitHelpers": true, "importHelpers": true, "strictNullChecks": false, "baseUrl": "./src", "paths": { "@angular/*": ["node_modules/@angular/*"] }, "lib": [ "dom", "es6", "es2017.object" ], "typeRoots": [ "node_modules/@types" ], "types": [ "jasmine", "hammerjs", "node", "source-map", "uglify-js", "webpack" ] }, "exclude": [ "node_modules", "dist" ], "awesomeTypescriptLoaderOptions": { "forkChecker": true, "useWebpackText": true }, "compileOnSave": false, "buildOnSave": false, "atom": { "rewriteTsconfig": false } } 

I'm "solving" this by compiling all files anyways and removing the unnecessary ones manually. In other words: a complete mess :P

Could you help me with this?