CppTools: Fix qbs build.

Change-Id: I0ef6e4419596b7cc0f8a574917fec5af94ff8832
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/plugins/cpptools/cpptools.qbs

 import qbs.base 1.0
+import qbs.fileinfo as FileInfo
 
 import "../QtcPlugin.qbs" as QtcPlugin
 import "../../../qbs/defaults.js" as Defaults
@@ -108,7 +109,14 @@ QtcPlugin {
 
     Group {
         condition: Defaults.testsEnabled(qbs)
-        files: ["cppcodegen_test.cpp", "cppcompletion_test.cpp"]
+        files: [
+            "cppcodegen_test.cpp",
+            "cppcompletion_test.cpp",
+            "cppmodelmanager_test.cpp",
+            "modelmanagertesthelper.cpp", "modelmanagertesthelper.h"
+        ]
+
+        cpp.defines: outer.concat(['SRCDIR="' + FileInfo.path(filePath) + '"'])
     }
 
     ProductModule {