Karma needs js files to be emitted

karma.conf.js

@@ -15,7 +15,7 @@ module.exports = function (config) {
     browsers: ['Chromium'],
     singleRun: true,
     karmaTypescriptConfig: {
-      tsconfig: './tsconfig.dev.json',
+      tsconfig: './tsconfig.karma.json',
       coverageOptions: {
         instrumentation: false,
       },

tsconfig.karma.json

@@ -0,0 +1,7 @@
+{
+  "extends": "./tsconfig",
+  "compilerOptions": {
+    "noEmit": false
+  },
+  "exclude": ["node_modules/**"]
+}