add tests for timer, add comments

thetawave_lib/src/spawn/systems/despawn.rs

@@ -108,7 +108,7 @@ mod test {
                 world.insert(EffectReturn(entity));
             })
             .with_assertion(|world| {
-                let entity = world.read_resource::<EffectReturn<Entity>>().0.clone();
+                let entity = world.read_resource::<EffectReturn<Entity>>().0;
                 world.maintain();
                 assert!(!world.is_alive(entity));
             })

thetawave_lib/src/tools/timer.rs

@@ -1,16 +1,30 @@
 use serde::{Deserialize, Serialize};
 
-/// Counts down a set amount of time then resets
+/// Counts down timer and resets
 #[derive(Serialize, Deserialize, Debug, Clone, Default)]
 pub struct Timer {
+    /// Amount of time between resets
     period: f32,
+    /// Remaining time until reset
     countdown: f32,
 }
 
 impl Timer {
-    /// Creates a new instance of Timer
-    /// Sets both the period and countdown to given value
+    /// Create a new instance of `Timer`
+    ///
+    /// # Parameters
+    ///
+    /// `period` - An `f32` length of the period
+    ///
+    /// # Returns
+    ///
+    /// A new instance of `Timer` with `period` and `countdown` set to the given period
+    ///
+    /// # Panics
+    ///
+    /// Panics when given period is less than or equal to zero.
     pub fn new(period: f32) -> Self {
+        Self::check_period(period);
         Timer {
             period,
             countdown: period,
@@ -41,11 +55,86 @@ impl Timer {
     }
 
     pub fn set_period(&mut self, period: f32) {
+        Self::check_period(period);
         self.period = period;
+        if self.countdown > self.period {
+            self.reset()
+        }
     }
 
     /// Returns the difference between the period and countdown
     pub fn get_time_left(&self) -> f32 {
         self.period - self.countdown
     }
+
+    fn check_period(period: f32) {
+        if period <= 0.0 {
+            panic!("Period of timer must be greater than zero.")
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn false_on_update_greater_than_zero() {
+        let mut timer = Timer::new(2.0);
+        assert!(!timer.update(1.0))
+    }
+
+    #[test]
+    fn true_on_update_equal_to_zero() {
+        let mut timer = Timer::new(1.0);
+        assert!(timer.update(1.0))
+    }
+
+    #[test]
+    fn true_on_update_less_than_zero() {
+        let mut timer = Timer::new(0.5);
+        assert!(timer.update(1.0))
+    }
+
+    #[test]
+    fn zero_time_left_on_reset() {
+        let mut timer = Timer::new(5.0);
+        timer.update(1.0);
+        timer.reset();
+        assert!(timer.get_time_left() == 0.0)
+    }
+
+    #[test]
+    fn zero_time_left_on_set_period_when_less_than_countdown() {
+        let mut timer = Timer::new(5.0);
+        timer.update(1.0);
+        timer.set_period(3.0);
+        assert!(timer.get_time_left() == 0.0);
+    }
+
+    #[test]
+    #[should_panic]
+    fn panic_on_new_with_zero_period() {
+        Timer::new(0.0);
+    }
+
+    #[test]
+    #[should_panic]
+    fn panic_on_new_with_negative_period() {
+        Timer::new(-1.0);
+    }
+
+    #[test]
+    #[should_panic]
+    fn panic_on_set_period_to_zero() {
+        let mut timer = Timer::new(1.0);
+        timer.set_period(0.0);
+    }
+
+    #[test]
+    #[should_panic]
+    fn panic_on_set_period_to_negative() {
+        let mut timer = Timer::new(1.0);
+        timer.set_period(-1.0);
+    }
 }