Octave: error() must be called with an argument

Examples/test-suite/octave/friends_runme.m

@@ -8,25 +8,25 @@ friends
 a = friends.A(2);
 
 if (friends.get_val1(a) != 2)
-  error
+  error("failed");
 endif
 if (friends.get_val2(a) != 4)
-  error
+  error("failed");
 endif
 if (friends.get_val3(a) != 6)
-  error
+  error("failed");
 endif
 
 				# nice overload working fine
 if (friends.get_val1(1,2,3) != 1)
-  error
+  error("failed");
 endif
 
 b = friends.B(3);
 
 				# David's case
 if (friends.mix(a,b) != 5)
-  error
+  error("failed");
 endif
 
 di = friends.D_d(2);
@@ -34,18 +34,18 @@ dd = friends.D_d(3.3);
 
 				# incredible template overloading working just fine
 if (friends.get_val1(di) != 2)
-  error
+  error("failed");
 endif
 if (friends.get_val1(dd) != 3.3)
-  error
+  error("failed");
 endif
 
 friends.set(di, 4);
 friends.set(dd, 1.3);
 
 if (friends.get_val1(di) != 4)
-  error
+  error("failed");
 endif
 if (friends.get_val1(dd) != 1.3)
-  error
+  error("failed");
 endif