tests: Addressed additional CR comments and added tests for tail-logs

src/utils_tests.rs

@@ -1,8 +1,11 @@
 #[cfg(test)]
 mod tests {
+  use std::fs::{self, File};
+  use std::io::{BufRead, BufReader, Seek, SeekFrom, Write};
+
   use pretty_assertions::assert_eq;
 
-  use crate::utils::{convert_f64_to_gb, convert_runtime, convert_to_gb};
+  use crate::utils::{convert_f64_to_gb, convert_runtime, convert_to_gb, was_log_rotated};
 
   #[test]
   fn test_convert_to_gb() {
@@ -23,4 +26,55 @@ mod tests {
     assert_eq!(hours, 2);
     assert_eq!(minutes, 34);
   }
+
+  #[test]
+  fn test_was_log_rotated_returns_false_when_file_has_not_rotated() {
+    let path = std::env::temp_dir().join("managarr_test_no_rotation.log");
+    fs::write(&path, "line one\nline two\n").unwrap();
+
+    let file = File::open(&path).unwrap();
+    let mut reader = BufReader::new(file);
+    reader.seek(SeekFrom::End(0)).unwrap();
+
+    assert!(!was_log_rotated(&path, &mut reader));
+
+    fs::remove_file(&path).unwrap();
+  }
+
+  #[test]
+  fn test_was_log_rotated_returns_true_and_reopens_reader_after_rotation() {
+    let path = std::env::temp_dir().join("managarr_test_rotation.log");
+    fs::write(&path, "original content that is long enough\n").unwrap();
+
+    let file = File::open(&path).unwrap();
+    let mut reader = BufReader::new(file);
+    reader.seek(SeekFrom::End(0)).unwrap();
+
+    fs::write(&path, "new\n").unwrap();
+
+    assert!(was_log_rotated(&path, &mut reader));
+
+    let mut line = String::new();
+    reader.read_line(&mut line).unwrap();
+    assert_eq!(line, "new\n");
+
+    fs::remove_file(&path).unwrap();
+  }
+
+  #[test]
+  fn test_was_log_rotated_returns_false_when_file_grows() {
+    let path = std::env::temp_dir().join("managarr_test_growing.log");
+    fs::write(&path, "initial\n").unwrap();
+
+    let file = File::open(&path).unwrap();
+    let mut reader = BufReader::new(file);
+    reader.seek(SeekFrom::End(0)).unwrap();
+
+    let mut appender = fs::OpenOptions::new().append(true).open(&path).unwrap();
+    appender.write_all(b"more data\n").unwrap();
+
+    assert!(!was_log_rotated(&path, &mut reader));
+
+    fs::remove_file(&path).unwrap();
+  }
 }