A method in a first radio network node for testing a transmission parameter value in a wireless communication system is provided. The first radio network node is configured to, during operational mode thereof, perform transmissions using available resources divided in to resource blocks. The first radio network node allocates a test resource block, for test purposes, among the available resources. The first radio network node defines for the test resource block, a test value for the transmission parameter. The test value differs from the nominal value. The first radio network node performs, during operational mode, a test transmission using the resource block. During the test transmission, the transmission parameter is set to the test value. The test transmission is configured to form the basis for an evaluation of the test value.