Problem: Dependency on googletest framework

Currently cppzmq as relatively simple and header only library depends on rather
complex unit test framework googletest.
Current issues:
- Googletest requires downloading and building it every time on travis
as cache support is limited there
- Googletest build is signifficant with comparison to cppzmq unittests
total runtime

Solution: Port existing tests to Catch - header only C++ framework and
gain ~20% build speed up on travis.

Why Catch?
It is well know C++ header only testing framework. It works well, it is
being kept up to date and maintainers seem to pay attention to
community's comments and issues.
We can not use Catch2 currently as we still support pre-C++11 compilers.

README.md

@@ -22,7 +22,7 @@ There are other C++ bindings for ZeroMQ with different design goals. In particul
 Supported platforms
 ===================
 
- - Only a subset of the platforms that are supported by libzmq itself are supported. Some features already require a compiler supporting C++11. In the future, probably all features will require C++11. To build and run the tests, cmake and googletest are required.
+ - Only a subset of the platforms that are supported by libzmq itself are supported. Some features already require a compiler supporting C++11. In the future, probably all features will require C++11. To build and run the tests, CMake and Catch are required.
  - Tested libzmq versions are
    - 4.2.0 (without DRAFT API)
    - 4.2.5 (with and without DRAFT API)

appveyor.yml

@@ -20,7 +20,7 @@ environment:
 
 cache:
     - libzmq -> appveyor.yml
-    - Build/tests/googletest -> tests/cmake/googletest-download.cmake
+    - Build/catch -> tests/cmake/catch.cmake
 
 before_build:
     - if not exist libzmq (

tests/CMakeLists.txt

@@ -9,11 +9,7 @@ set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_LIBDIR})
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_LIBDIR})
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_BINDIR})
 
-include(cmake/googletest.cmake)
-fetch_googletest(
-    ${PROJECT_SOURCE_DIR}/cmake
-    ${PROJECT_BINARY_DIR}/googletest
-    )
+include(cmake/catch.cmake)
 
 add_executable(
     unit_tests
@@ -24,14 +20,15 @@ add_executable(
     active_poller.cpp
     multipart.cpp
 	monitor.cpp
-    )
+)
 
+add_dependencies(unit_tests catch)
+
+target_include_directories(unit_tests PUBLIC ${CATCH_INCLUDE_DIR})
 target_link_libraries(
     unit_tests
-	PRIVATE gtest
-	PRIVATE gmock_main
     PRIVATE cppzmq
-    )
+)
 
 OPTION (COVERAGE "Enable gcda file generation needed by lcov" OFF)
 
@@ -45,4 +42,4 @@ add_test(
     unit
   COMMAND
     ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_BINDIR}/unit_tests
-  )
+)