The following is an example of how to use the withFormParam method to customize the response of a stub based on the value of a from parameter.
WireMock.stubFor(post(urlEqualTo("/my-endpoint"))
.withHeader("Content-Type", containing("application/x-www-form-urlencoded"))
.withFormParam("field1", equalTo("value1"))
.willReturn(aResponse()
.withStatus(200)
.withBody("Response for field1=value1")));The withFormParam method was implemented in WireMock 3.0.0 release.