chore(build): add coverage target

CMakeLists.txt

@@ -18,7 +18,12 @@ project(storm)
 
 set(CMAKE_CXX_STANDARD 11)
 
-include(lib/system/cmake/system.cmake)
+list(APPEND CMAKE_MODULE_PATH
+    "${CMAKE_CURRENT_SOURCE_DIR}/lib/system/cmake"
+    "${CMAKE_CURRENT_SOURCE_DIR}/vendor/cmake-modules"
+)
+
+include(system)
 
 # OS defines
 if(WHOA_SYSTEM_WIN)
@@ -30,5 +35,27 @@ if(WHOA_SYSTEM_WIN)
 endif()
 
 add_subdirectory(lib)
+
+if(CMAKE_COMPILER_IS_GNUCXX AND CMAKE_BUILD_TYPE STREQUAL "Debug")
+    # Running coverage on linux+gcc:
+    #
+    #   sudo apt install lcov
+    #   cmake -DCMAKE_BUILD_TYPE=Debug ..
+    #   make
+    #   make StormCoverage
+    #
+    # Results in `StormCoverage/index.html`
+    include(CodeCoverage)
+
+    setup_target_for_coverage_lcov(
+        NAME StormCoverage
+        EXECUTABLE StormTest
+        DEPENDENCIES StormTest storm
+        BASE_DIRECTORY "${PROJECT_SOURCE_DIR}/storm"
+        LCOV_ARGS --rc branch_coverage=1
+        GENHTML_ARGS --rc genhtml_branch_coverage=1
+    )
+endif()
+
 add_subdirectory(storm)
 add_subdirectory(test)