tests and updated error type

src/defense.rs

@@ -102,7 +102,7 @@ impl LevelBuilder {
     /// build Level struct
     pub fn build(&mut self) -> CaptchaResult<Level> {
         if self.visitor_threshold.is_none() {
-            Err(CaptchaError::SetVisitorCount)
+            Err(CaptchaError::SetVisitorThreshold)
         } else if self.difficulty_factor.is_none() {
             Err(CaptchaError::SetDifficultyFactor)
         } else {
@@ -248,6 +248,18 @@ mod tests {
             LevelBuilder::default().difficulty_factor(0),
             Err(CaptchaError::DifficultyFactorZero)
         );
+
+        assert_eq!(
+            LevelBuilder::default()
+                .difficulty_factor(1)
+                .unwrap()
+                .build(),
+            Err(CaptchaError::SetVisitorThreshold)
+        );
+        assert_eq!(
+            LevelBuilder::default().visitor_threshold(10).build(),
+            Err(CaptchaError::SetDifficultyFactor)
+        );
     }
 
     #[test]

src/errors.rs

@@ -38,9 +38,9 @@ pub enum CaptchaError {
     #[display(fmt = "Set difficulty factor")]
     SetDifficultyFactor,
 
-    /// Visitor count must be set
-    #[display(fmt = "Set visitor count")]
-    SetVisitorCount,
+    /// Visitor threshold must be set
+    #[display(fmt = "Set visitor threshold")]
+    SetVisitorThreshold,
 
     /// Visitor count must be Unique
     #[display(fmt = "Duplicate visitor count")]