diff --git a/src/population.rs b/src/population.rs
index 1ae1bba..6a97d9b 100644
--- a/src/population.rs
+++ b/src/population.rs
@@ -61,7 +61,6 @@ fn humans_stats(humans: &Vec<Human>) -> Stats {
     stats
 }
 
-
 impl Population {
     pub fn new(
         start_infected_ratio: u32,
@@ -100,11 +99,17 @@ impl Population {
         let mut rng = rand::thread_rng();
 
         for x in self.humans.iter_mut() {
-            if (self.start_infected_ratio) > 0 && (rng.gen_range(0..CORRECTED_PERCENTAGE) <= self.start_infected_ratio as i32) {
+            if (self.start_infected_ratio) > 0
+                && (rng.gen_range(0..CORRECTED_PERCENTAGE) <= self.start_infected_ratio as i32)
+            {
                 x.present_state = State::Infected;
-            } else if self.start_immune_ratio > 0 && rng.gen_range(0..CORRECTED_PERCENTAGE) <= self.start_immune_ratio as i32 {
+            } else if self.start_immune_ratio > 0
+                && rng.gen_range(0..CORRECTED_PERCENTAGE) <= self.start_immune_ratio as i32
+            {
                 x.present_state = State::Immune;
-            } else if self.start_dead_ratio > 0 && rng.gen_range(0..CORRECTED_PERCENTAGE) <= self.start_dead_ratio as i32 {
+            } else if self.start_dead_ratio > 0
+                && rng.gen_range(0..CORRECTED_PERCENTAGE) <= self.start_dead_ratio as i32
+            {
                 x.present_state = State::Dead;
             }
         }
@@ -361,7 +366,10 @@ mod tests {
         let population = Population::new(20, 10, 5, 5, 7, disease);
         assert_eq!(population.humans.len(), 5 * 7);
         for human in population.humans.iter() {
-            assert!(human.present_state == State::Normal, "all humans should be normal");
+            assert!(
+                human.present_state == State::Normal,
+                "all humans should be normal"
+            );
         }
     }
 
@@ -415,31 +423,46 @@ mod tests {
         stats = humans_stats(&population.humans);
         println!("should be dead: {:?}", stats);
         assert_eq!(stats.dead, width * height);
-
     }
 
-    #[parameterized(infection_rate = {0, 100}, infected_expected = {0, 1})]
-    fn propage_test(infection_rate: u32, infected_expected: i32) {
+    #[parameterized(infection_rate = {0, 100, 0}, death_rate = {0, 0, 100}, infected_expected = {0, 1, 1})]
+    fn propage_test(
+        infection_rate: u32,
+        death_rate: u32,
+        infected_expected: i32,
+    ) {
         let disease: Disease;
         let mut population: Population;
         let mut stats: Stats;
         let (width, height) = (100, 100);
         let start_infected = 50;
 
-        disease = Disease::new(infection_rate, 0, 0, String::from("Test"));
-        population = Population::new(start_infected, 0, 0, width, height, disease);
-        stats = humans_stats(&population.humans);
-        println!("Population: {:?}", stats);
+        println!("infection rate: {}, death_rate: {}", infection_rate, death_rate);
 
-        // total * proba - 20% < infected < total * proba + 20%
-        let expected_infected = width * height * start_infected as i32 / 100;
-        let tolerance = ((width * height) as f32 * 0.2) as i32;
-        assert!(stats.infected < expected_infected + tolerance);
-        assert!(stats.infected > expected_infected - tolerance);
+        disease = Disease::new(infection_rate, 0, death_rate, String::from("Test"));
+        population = Population::new(start_infected, 0, 0, width, height, disease);
 
         population.generate();
+        stats = humans_stats(&population.humans);
+        println!("Population after generate: {:?}", stats);
+
+        // total * proba - 20% < infected < total * proba + 20%
+        let infected_at_start = width * height * start_infected as i32 / 100;
+        let infected_tolerance = ((width * height) as f32 * 0.2) as i32;
+        assert!(stats.infected < infected_at_start + infected_tolerance);
+        assert!(stats.infected > infected_at_start - infected_tolerance);
+        assert_eq!(stats.dead, 0);
+
         population.propagate();
         stats = humans_stats(&population.humans);
-        assert!(stats.normal <= width * height * infected_expected);
+        println!("Population after propagate: {:?}", stats);
+
+        assert!(stats.normal <= infected_at_start + width * height * infected_expected);
+
+        let should_be_dead = infected_at_start * death_rate as i32 / 100;
+        let dead_tolerance = (should_be_dead as f32 * 0.20) as i32;
+
+        assert!(stats.dead < should_be_dead + dead_tolerance);
+        assert!(stats.dead > should_be_dead - dead_tolerance);
     }
 }