Fix missing newlines in list files

src/output.rs

@@ -195,7 +195,7 @@ impl OutputDir {
                 SummaryOutcome::Unviable => &mut self.unviable_list,
                 _ => return Ok(()),
             };
-            write!(file, "{}", mutant.format_as_error_message()).context("write to list file")?;
+            writeln!(file, "{}", mutant.format_as_error_message()).context("write to list file")?;
         }
         Ok(())
     }

tests/cli.rs

@@ -585,6 +585,7 @@ fn well_tested_tree_finds_no_problems() {
         .path()
         .join("mutants.out/outcomes.json")
         .exists());
+    check_text_list_output(tmp_src_dir.path(), "well_tested_tree_finds_no_problems");
 }
 
 #[test]

tests/snapshots/cli__well_tested_tree_finds_no_problems__caught.txt.snap

@@ -0,0 +1,20 @@
+---
+source: tests/cli.rs
+expression: content
+---
+src/inside_mod.rs:3: replace outer::inner::name with Default::default()
+src/methods.rs:16: replace Foo::double with ()
+src/methods.rs:22: replace <impl Display for Foo>::fmt with Ok(Default::default())
+src/methods.rs:28: replace <impl Debug for &Foo>::fmt with Ok(Default::default())
+src/nested_function.rs:1: replace has_nested with Default::default()
+src/nested_function.rs:2: replace has_nested::inner with Default::default()
+src/result.rs:5: replace simple_result with Ok(Default::default())
+src/result.rs:9: replace error_if_negative with Ok(Default::default())
+src/simple_fns.rs:7: replace returns_unit with ()
+src/simple_fns.rs:12: replace returns_42u32 with Default::default()
+src/simple_fns.rs:17: replace divisible_by_three with true
+src/simple_fns.rs:17: replace divisible_by_three with false
+src/simple_fns.rs:26: replace double_string with "".into()
+src/simple_fns.rs:26: replace double_string with "xyzzy".into()
+src/struct_with_lifetime.rs:14: replace Lex<'buf>::buf_len with Default::default()
+

tests/snapshots/cli__well_tested_tree_finds_no_problems__missed.txt.snap

@@ -0,0 +1,5 @@
+---
+source: tests/cli.rs
+expression: content
+---
+

tests/snapshots/cli__well_tested_tree_finds_no_problems__timeout.txt.snap

@@ -0,0 +1,5 @@
+---
+source: tests/cli.rs
+expression: content
+---
+

tests/snapshots/cli__well_tested_tree_finds_no_problems__unviable.txt.snap

@@ -0,0 +1,5 @@
+---
+source: tests/cli.rs
+expression: content
+---
+