sort: add test for sorting a file which triggers a buffer resize

src/uu/sort/src/ext_sort.rs

@@ -36,6 +36,7 @@ use crate::{
 };
 use crate::{Line, print_sorted};
 
+// Note: update `test_sort::test_start_buffer` if this size is changed
 const START_BUFFER_SIZE: usize = 8_000;
 
 /// Sort files by using auxiliary files for storing intermediate chunks (if needed), and output the result.

tests/by-util/test_sort.rs

@@ -1906,4 +1906,10 @@ fn test_color_environment_variables() {
     }
 }
 
+#[test]
+fn test_start_buffer() {
+    // Test that a file with the exact same size as the start buffer is handled correctly
+    test_helper("start_buffer_b", &["start_buffer_a.txt"]);
+}
+
 /* spell-checker: enable */

tests/fixtures/sort/start_buffer_a.txt

@@ -0,0 +1 @@
+aaa