Skip .spec files only for SonarTS and not TSLint

I want to set up SonarTS inside of my Angular 6 project, but when running my lint npm script I get code analysis of my .spec files too. Sometimes duplication in my .spec files is desirable, so how can I deactivate this, without skipping linting for my .spec files?

npm script in package.json

"lint": "tslint -p src/tsconfig.tslint.json -t stylish -c tslint.json",

devDependency in package.json

"tslint-sonarts": "^1.7.0",

tslint.json

"extends": [
    "@ns/tslint-presets/tslint.recommended.angular.json",
    "tslint-config-prettier",
    "tslint-sonarts"
],

tsconfig.json (this also skips linting, not desired!)

"exclude": [
    "node_modules",
    "**/*.spec.ts"
],