fixing the roll function

src/population.rs

@@ -151,12 +151,13 @@ impl Population {
             //now we can start to check if people would be infected or not
             //let idx = human_idx(pos.x as i32, pos.y as i32, self.width as i32);
             if pos.x > 0 && pos.x < self.width - 1 && pos.y > 0 && pos.y < self.height - 1 {
-                if self.roll(self.plague.curing_rate) {
+                if Population::roll(self.plague.curing_rate) {
-                    //checks if the man dies
+                    //checks if the man recovers
                     people_to_cure.push(Point { x: pos.x, y: pos.y });
                 } else {
-                    if self.roll(self.plague.death_rate) {
+                    if Population::roll(self.plague.death_rate) {
                         //cheks if the man dies
+                        println!("someone should die");
                         people_to_kill.push(Point { x: pos.x, y: pos.y });
                     } else {
                         let mut possible_infections: Vec<Point> = Vec::with_capacity(8);
@@ -203,7 +204,7 @@ impl Population {
                             let inf_idx =
                                 human_idx(poss_infected_pos.x, poss_infected_pos.y, self.width);
                             if self.humans[inf_idx].present_state == State::Normal {
-                                if self.roll(self.plague.infection_rate) {
+                                if Population::roll(self.plague.infection_rate) {
                                     people_to_infect.push(Point {
                                         x: poss_infected_pos.x,
                                         y: poss_infected_pos.y,
@@ -219,7 +220,7 @@ impl Population {
 
                 //REMOVE WHEN IMPLEMENTED
                 //It is here to prevent an infected in the borders to keep the programm running as he thinks there are still people to simulate
-                people_to_kill.push(Point { x: pos.x, y: pos.y });
+                //people_to_kill.push(Point { x: pos.x, y: pos.y });
 
                 //    @##
                 //    ###
@@ -292,7 +293,7 @@ impl Population {
         }
         stats
     }
-    pub fn roll(&self, probability: u32) -> bool {
+    pub fn roll(probability: u32) -> bool {
         let mut rng = rand::thread_rng();
         rng.gen_range(0..CORRECTED_PERCENTAGE) <= probability as i32
     }
@@ -425,6 +426,18 @@ mod tests {
         assert_eq!(stats.dead, width * height);
     }
 
+    #[parameterized(rate = {0, 100}, expected = {false, true})]
+    fn roll_test(rate: u32, expected: bool) {
+        let tries = 1000;
+        let mut result = 0;
+        for _x in 0..1000 {
+            if Population::roll(rate) == expected {
+                result += 1;
+            }
+        }
+        assert_eq!(result, tries);
+    }
+
     #[parameterized(infection_rate = {0, 100, 0}, death_rate = {0, 0, 100}, infected_expected = {0, 1, 1})]
     fn propage_test(
         infection_rate: u32,
@@ -455,7 +468,11 @@ mod tests {
 
         let infected_at_start = stats.infected;
 
-        population.propagate();
+        let propa_stats: [i32; 4] = population.propagate();
+        if death_rate == 0 {
+            assert_eq!(propa_stats[3], 0, "no human should have died");
+        }
+
         stats = humans_stats(&population.humans);
         println!("Population after propagate: {:?}", stats);