Number the tests with padding so that they will correctly alphabetise

Author: thk123

src/cbmc/bmc_cover.cpp

@@ -335,7 +335,7 @@ bool bmc_covert::operator()()
       // Compute the test code
       test.source_code=gen.generate_tests(bmc.options,bmc.ns.get_symbol_table(),
                                                    goto_functions,test.goto_trace,
-                                                   ++test_case_no,goal_names);
+                                                   test_case_no,goal_names);
 
       ++test_case_no;
     }

src/test-c-gen/c_test_case_generator.cpp

@@ -45,7 +45,9 @@ const std::string c_test_case_generatort::get_test_function_name(
 
   std::ostringstream test_name;
 
-  test_name << sanitised_name << "_" << test_idx;
+
+  test_name << sanitised_name << "_";
+  test_name << std::setfill('0') << std::setw(3) << test_idx;
 
   return test_name.str();
 }