You could use a dynamic port, with the below code
int port = org.springframework.util.SocketUtils.findAvailableTcpPort();
WireMockServer wireMockServer = new WireMockServer(wireMockConfig().port(port)); wireMockServer.start();
int port = org.springframework.util.SocketUtils.findAvailableTcpPort();
WireMockServer wireMockServer = new WireMockServer(wireMockConfig().port(port));
wireMockServer.start();