if: Add test for IS_DIRECTORY

Add a RunCMake.if test to cover if() command behavior.  Start with a
test for IS_DIRECTORY cases with an existing directory and a long path,
both with a trailing slash.

Tests/RunCMake/CMakeLists.txt

@@ -72,6 +72,7 @@ add_RunCMake_test(add_dependencies)
 add_RunCMake_test(build_command)
 add_RunCMake_test(find_package)
 add_RunCMake_test(get_filename_component)
+add_RunCMake_test(if)
 add_RunCMake_test(include)
 add_RunCMake_test(include_directories)
 add_RunCMake_test(list)

Tests/RunCMake/if/CMakeLists.txt

@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 2.8)
+project(${RunCMake_TEST} NONE)
+include(${RunCMake_TEST}.cmake)

Tests/RunCMake/if/IsDirectory-stdout.txt

@@ -0,0 +1 @@
+CMAKE_CURRENT_SOURCE_DIR exists, tested with trailing slash

Tests/RunCMake/if/IsDirectory.cmake

@@ -0,0 +1,5 @@
+if(IS_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/")
+  message(STATUS "CMAKE_CURRENT_SOURCE_DIR exists, tested with trailing slash")
+else()
+  message(FATAL_ERROR "CMAKE_CURRENT_SOURCE_DIR does not exist!")
+endif()

Tests/RunCMake/if/IsDirectoryLong-stdout.txt

@@ -0,0 +1 @@
+Directory path with length 94208 correctly does not exist.

Tests/RunCMake/if/IsDirectoryLong.cmake

@@ -0,0 +1,10 @@
+set(d "/long/path/to/directory")
+foreach(i RANGE 11)
+  set(d "${d}${d}")
+endforeach()
+string(LENGTH "${d}" dl)
+if(IS_DIRECTORY "${d}/")
+  message(FATAL_ERROR "Directory should not exist!")
+else()
+  message(STATUS "Directory path with length ${dl} correctly does not exist.")
+endif()

Tests/RunCMake/if/RunCMakeTest.cmake

@@ -0,0 +1,4 @@
+include(RunCMake)
+
+run_cmake(IsDirectory)
+run_cmake(IsDirectoryLong)