Fix bug in jump code

that always causes damage during jump.
Attempt to fix drive test.

engine/CMakeLists.txt

@@ -1752,6 +1752,7 @@ IF (USE_GTEST)
         src/exit_unit_tests.cpp
         src/components/tests/energy_container_tests.cpp
         src/components/tests/balancing_tests.cpp
+        src/components/tests/jump_drive_tests.cpp
     )
 
     ADD_LIBRARY(vegastrike-testing

engine/src/cmd/unit_functions_generic.cpp

@@ -36,7 +36,7 @@
 #include "universe.h"
 #include "mount_size.h"
 #include "damageable.h"
-
+#include "resource/random_utils.h"
 
 //Various functions that were used in .cpp files that are now included because of
 //the temple GameUnit class
@@ -255,10 +255,10 @@ void DealPossibleJumpDamage(Unit *un) {
     static double max_damage = XMLSupport::parse_float(vs_config->getVariable("physics", "max_jump_damage", "100"));
 
     // Also damage multiplier
-    double chance_to_damage = ((double) rand() / (RAND_MAX)) + 1;
+    double chance_to_damage = randomDouble() - 0.01;
 
     // If jump drive is fully operational, there's no chance for damage
-    if(un->jump_drive.Operational() >= chance_to_damage) {
+    if(un->jump_drive.Percent() >= chance_to_damage) {
         return;
     }
 

engine/src/components/tests/jump_drive_tests.cpp

@@ -0,0 +1,66 @@
+/*
+ * jump_drive_tests.cpp
+ *
+ * Copyright (C) 2001-2023 Daniel Horn, Benjamen Meyer, Roy Falk, Stephen G. Tuggy,
+ * and other Vega Strike contributors.
+ *
+ * https://github.com/vegastrike/Vega-Strike-Engine-Source
+ *
+ * This file is part of Vega Strike.
+ *
+ * Vega Strike is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Vega Strike is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Vega Strike. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <gtest/gtest.h>
+#include <map>
+
+#include "jump_drive.h"
+#include "resource/random_utils.h"
+#include "unit_csv_factory.h"
+
+static const std::string upgrades_suffix_string = "__upgrades";
+static const std::string jump_drive_string = "jump_drive";
+
+static const std::map<std::string,std::string> jump_drive_map = {
+    {"Key", "jump_drive__upgrades"},
+    {"Name", "Interstellar Jump Drive"},
+    {"Upgrade_Type", "Jump_Drive"},
+    {"Object_Type", "Upgrade_Replacement"},
+    {"Textual_Description", "\"@upgrades/jump_drive.png@Jump drive for traveling between stars\"\n"},
+    {"Mass", "10"},
+    {"Moment_Of_Inertia", "10"},
+    {"Jump_Drive_Present", "TRUE"},
+    {"Jump_Drive_Delay", "1"}
+};
+
+
+
+// Used to quickly figure out why the code wasn't working properly
+TEST(JumpDrive, Damage) {
+    UnitCSVFactory::LoadUnit(jump_drive_string + upgrades_suffix_string, jump_drive_map);
+
+    JumpDrive jump_drive;
+
+    jump_drive.Load("", jump_drive_string + upgrades_suffix_string);
+
+    jump_drive.DamageByPercent(0.1);
+
+    // Check operational drive shouldn't get damage
+    double chance_to_damage = randomDouble() - 0.01;
+
+    std::cout << chance_to_damage << std::endl;
+    std::cout << jump_drive.Percent() << std::endl;
+
+    //EXPECT_FALSE(true);
+}