code: function setupFakeDocumentBaseHref( fakeBase ) {
        // First call: to determine the base href:
        browserMock.resolve.and.callFake( ( url, base ) => {
           // Second call: to resolve the (already absolute) router base against the document base:
           browserMock.resolve.and.callFake( ( url, origin ) => {
              const fakeOrigin = `${locationMock.protocol}://${locationMock.hostname}:${locationMock.port}`;
              expect( url ).toEqual( fakeBase );
              expect( origin ).toEqual( fakeOrigin );
              return url;
           } );
           expect( url ).toEqual( '.' );
           expect( base ).not.toBeDefined();
           return fakeBase;
        } );
     }
docs: Allow to fake that the document contains a base element with an (external) base href, so that it is used if the router base is not defined.