Minor linting tweaks

.clippy.toml

@@ -1,2 +1,3 @@
 allow-unwrap-in-tests = true
 allow-expect-in-tests = true
+single-char-binding-names-threshold = 2

Cargo.toml

@@ -124,6 +124,7 @@ ref_option_ref = "warn"
 return_self_not_must_use = "warn"
 same_functions_in_if_condition = "warn"
 semicolon_if_nothing_returned = "warn"
+set_contains_or_insert = "warn"
 should_panic_without_expect = "warn"
 similar_names = "warn"
 str_split_at_newline = "warn"

src/dev.rs

@@ -92,7 +92,7 @@ mod tests {
 
     #[test]
     fn wrap_newline() {
-        assert_eq!(wrap("\n"), String::from(r"↳"));
+        assert_eq!(wrap("\n"), String::from("↳"));
     }
 
     #[test]