Improve unit tests in tokenclient_test.go

Also fix a linter error and rename some new files.

internal/controller/impersonatorconfig/impersonator_config_test.go

@@ -274,7 +274,7 @@ func TestImpersonatorConfigControllerSync(t *testing.T) {
 		const httpsPort = ":443"
 		const fakeServerResponseBody = "hello, world!"
 		const externallyProvidedTLSSecretName = "external-tls-secret" //nolint:gosec // this is not a credential
-		fakeExpiringSingletonTokenCacheGet := *new(tokenclient.ExpiringSingletonTokenCacheGet)
+		var fakeExpiringSingletonTokenCacheGet = tokenclient.NewExpiringSingletonTokenCache()
 		var labels = map[string]string{"app": "app-name", "other-key": "other-value"}
 
 		var r *require.Assertions

internal/controller/serviceaccounttokencleanup/service_account_token_cleanup_controller_test.go

@@ -132,6 +132,8 @@ func TestSync(t *testing.T) {
 	} {
 		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			kubeAPIClient, kubeInformers := setupKubernetes(t, tt.namespace)
 			if tt.addReactors != nil {
 				tt.addReactors(kubeAPIClient)