Test dirty flags on all FAT variants

Flags field offset is different is it makes sense.

tests/write.rs

@@ -306,9 +306,7 @@ fn test_rename_file_fat32() {
     call_with_fs(&test_rename_file, FAT32_IMG, 6)
 }
 
-#[test]
-fn test_dirty_flag() {
-    call_with_tmp_img(&|tmp_path| {
+fn test_dirty_flag(tmp_path: &str) {
     // Open filesystem, make change, and forget it - should become dirty
     let fs = open_filesystem_rw(tmp_path);
     let status_flags = fs.read_status_flags().unwrap();
@@ -327,5 +325,19 @@ fn test_dirty_flag() {
     let status_flags = fs.read_status_flags().unwrap();
     assert_eq!(status_flags.dirty(), true);
     assert_eq!(status_flags.io_error(), false);
-    }, FAT32_IMG, 7);
+}
+
+#[test]
+fn test_dirty_flag_fat12() {
+    call_with_tmp_img(&test_dirty_flag, FAT12_IMG, 7)
+}
+
+#[test]
+fn test_dirty_flag_fat16() {
+    call_with_tmp_img(&test_dirty_flag, FAT16_IMG, 7)
+}
+
+#[test]
+fn test_dirty_flag_fat32() {
+    call_with_tmp_img(&test_dirty_flag, FAT32_IMG, 7)
 }