Plotly object not found on window" when unit testing a component

[SkCodeRains]

Error: Plotly object not found on window.
Error: Plotly object not found on window. at new PlotlyViaWindowModule (http://localhost:9876/_karma_webpack_/webpack:/node_modules/angular-plotly.js/fesm2015/angular-plotly.js.js:634:1) at Object.PlotlyViaWindowModule_Factory [as factory] (http://localhost:9876/_karma_webpack_/webpack:/node_modules/angular-plotly.js/fesm2015/angular-plotly.js.js:639:74) at R3Injector.hydrate (http://localhost:9876/_karma_webpack_/webpack:/node_modules/@angular/core/fesm2015/core.js:11457:1) at R3Injector.get (http://localhost:9876/_karma_webpack_/webpack:/node_modules/@angular/core/fesm2015/core.js:11276:1) at http://localhost:9876/_karma_webpack_/webpack:/node_modules/@angular/core/fesm2015/core.js:11314:1 at Set.forEach (<anonymous>) at R3Injector._resolveInjectorDefTypes (http://localhost:9876/_karma_webpack_/webpack:/node_modules/@angular/core/fesm2015/core.js:11314:1) at new NgModuleRef$1 (http://localhost:9876/_karma_webpack_/webpack:/node_modules/@angular/core/fesm2015/core.js:25345:1) at R3TestBedCompiler.finalize (http://localhost:9876/_karma_webpack_/webpack:/node_modules/@angular/core/fesm2015/testing.js:926:1) at TestBedRender3.get testModuleRef [as testModuleRef] (http://localhost:9876/_karma_webpack_/webpack:/node_modules/@angular/core/fesm2015/testing.js:1789:1)