Unknown CMake command "add_rostest"

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I am new to ROS and trying to go through the Creating a workspace tutorial. I follow everything properly and run ~/ros/overlay_ws$ catkin_make -DPYTHON_EXECUTABLE=/usr/bin/python3.

CMake Warning at ros_tutorials/rospy_tutorials/CMakeLists.txt:102 (find_package):
  By not providing "Findrostest.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "rostest", but
  CMake did not find one.

  Could not find a package configuration file provided by "rostest" with any
  of the following names:

    rostestConfig.cmake
    rostest-config.cmake

  Add the installation prefix of "rostest" to CMAKE_PREFIX_PATH or set
  "rostest_DIR" to a directory containing one of the above files.  If
  "rostest" provides a separate development package or SDK, be sure it has
  been installed.


CMake Error at ros_tutorials/rospy_tutorials/CMakeLists.txt:112 (add_rostest):
  Unknown CMake command "add_rostest".


-- Configuring incomplete, errors occurred!
See also "/home/pra-dan/ros/overlay_ws/build/CMakeFiles/CMakeOutput.log".
See also "/home/pra-dan/ros/overlay_ws/build/CMakeFiles/CMakeError.log".
Invoking "cmake" failed

What is wrong here ?