add round_chunk_item_size test case

Author: sokra

turbopack/crates/turbopack-core/src/chunk/mod.rs

@@ -714,15 +714,8 @@ pub trait ChunkType: ValueToString {
 }
 
 pub fn round_chunk_item_size(size: usize) -> usize {
-    if size == 0 {
-        return 0;
-    }
     let a = size.next_power_of_two();
-    if a == size {
-        size
-    } else {
-        size & (a | (a >> 1) | (a >> 2))
-    }
+    size & (a | (a >> 1) | (a >> 2))
 }
 
 #[turbo_tasks::value(transparent)]
@@ -764,3 +757,43 @@ where
         chunk_item.chunking_context().chunk_item_id(chunk_item)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_round_chunk_item_size() {
+        assert_eq!(round_chunk_item_size(0), 0);
+        assert_eq!(round_chunk_item_size(1), 1);
+        assert_eq!(round_chunk_item_size(2), 2);
+        assert_eq!(round_chunk_item_size(3), 3);
+        assert_eq!(round_chunk_item_size(4), 4);
+        assert_eq!(round_chunk_item_size(5), 4);
+        assert_eq!(round_chunk_item_size(6), 6);
+        assert_eq!(round_chunk_item_size(7), 6);
+        assert_eq!(round_chunk_item_size(8), 8);
+
+        assert_eq!(changes_in_range(0..1000), 19);
+        assert_eq!(changes_in_range(1000..2000), 2);
+        assert_eq!(changes_in_range(2000..3000), 1);
+
+        assert_eq!(changes_in_range(3000..10000), 4);
+
+        fn changes_in_range(range: std::ops::Range<usize>) -> usize {
+            let len = range.len();
+            let mut count = 0;
+            for i in range {
+                let a = round_chunk_item_size(i);
+                assert!(a >= i * 2 / 3);
+                assert!(a <= i);
+                let b = round_chunk_item_size(i + 1);
+
+                if a == b {
+                    count += 1;
+                }
+            }
+            len - count
+        }
+    }
+}