New test to find duplicate feed entries

tests/feed_validation.rs

@@ -1,3 +1,4 @@
+use std::collections::HashMap;
 use std::collections::HashSet;
 use std::fs;
 
@@ -29,3 +30,28 @@ fn test_if_feeds_lists_have_overlapping_feed() {
     let set2: HashSet<_> = read_feed("featured_feeds.txt").into_iter().collect();
     assert!(set1.is_disjoint(&set2));
 }
+
+#[test]
+fn test_if_duplicates_in_feeds_list() {
+    let mut urls = read_feed("feeds.txt");
+
+    urls.sort();
+
+    let duplicates = urls
+        .into_iter()
+        .fold(HashMap::new(), |mut map, x| {
+            *map.entry(x).or_insert(0) += 1;
+            map
+        })
+        .into_iter()
+        .filter(|(_, count)| *count > 1)
+        .map(|(item, _)| item)
+        .collect::<Vec<String>>();
+
+    if !duplicates.is_empty() {
+        for dupe in duplicates {
+            println!("{}", dupe)
+        }
+        panic!("Duplicate entries found!")
+    }
+}