Nevermind, needed to actually throw an exception object.

include/jtest/jtest.hpp

@@ -12,7 +12,7 @@ namespace jtest {
 
     bool check(bool condition) {
         if (!condition)
-            throw;
+            throw std::runtime_error("Test check failed!!");
         return condition;
     }
 

main.cpp

@@ -22,5 +22,6 @@ int main()
         jtest::check(2+2 == 5);
     });
 
+    // Doesn't actually do anything yet
     jtest::run_tests();
 }