Added ZMQ_BUILD_TESTS to CMakeLists.txt to allow turning off tests. Useful when building ZMQ as a git submodule.

CMakeLists.txt

@@ -580,8 +580,14 @@ if(NOT CMAKE_BUILD_TYPE STREQUAL "Debug") # Why?
   endforeach()
 endif()
 
-enable_testing()
-set(tests
+#-----------------------------------------------------------------------------
+# tests
+
+set(ZMQ_BUILD_TESTS ON CACHE BOOL "Build the tests for ZeroMQ")
+
+if(ZMQ_BUILD_TESTS)
+  enable_testing()
+  set(tests
           test_system
           test_pair_inproc
           test_pair_tcp
@@ -623,9 +629,9 @@ set(tests
           test_many_sockets
           test_diffserv
           test_connect_rid
-)
-if(NOT WIN32)
-list(APPEND tests
+  )
+  if(NOT WIN32)
+  list(APPEND tests
           test_monitor
           test_pair_ipc
           test_reqrep_ipc
@@ -633,10 +639,10 @@ list(APPEND tests
           test_abstract_ipc
           test_proxy
           test_filter_ipc
-)
-endif()
+  )
+  endif()
 
-foreach(test ${tests})
+  foreach(test ${tests})
     add_executable(${test} tests/${test}.cpp)
     target_link_libraries(${test} libzmq)
 
@@ -648,13 +654,15 @@ foreach(test ${tests})
     else()
       add_test(NAME ${test} COMMAND ${test})
     endif()
-endforeach()
+  endforeach()
 
-if(NOT WIN32)
+  if(NOT WIN32)
     if(NOT CMAKE_SYSTEM_NAME MATCHES "Linux")
       set_tests_properties(test_abstract_ipc PROPERTIES WILL_FAIL true)
     endif()
-endif()
+  endif()
+
+endif() # ZMQ_BUILD_TESTS
 
 #-----------------------------------------------------------------------------
 # installer