Octave: error() must be called with an argument

Examples/test-suite/octave/callback_runme.m

@@ -2,39 +2,39 @@ _callback
 callback
 
 if (foo(2) != 2)
-  error
+  error("failed");
 endif
 
 if (A_bar(2) != 4)
-  error
+  error("failed");
 endif
 
 if (foobar(3, _callback.foo) != foo(3))
-  error  
+  error("failed");
 endif
 
 if (foobar(3, foo) != foo(3))
-  error  
+  error("failed");
 endif
 
 if (foobar(3, A_bar) != A_bar(3))
-  error
+  error("failed");
 endif
 
 if (foobar(3, foof) != foof(3))
-  error
+  error("failed");
 endif
 
 if (foobar_i(3, foo_i) != foo_i(3))
-  error
+  error("failed");
 endif
 
 
 if (foobar_d(3.5, foo_d) != foo_d(3.5))
-  error
+  error("failed");
 endif
 
 a = A();
 if (foobarm(3, a, A.foom_cb_ptr) != a.foom(3))
-  error
+  error("failed");
 endif