test(ser): Port another test from toml-rs

tests/formatter.rs

@@ -0,0 +1,55 @@
+#![cfg(feature = "easy")]
+
+use serde::{Deserialize, Serialize};
+use toml_edit::ser::to_string;
+
+#[derive(Debug, Clone, Hash, PartialEq, Eq, Serialize, Deserialize)]
+struct User {
+    pub name: String,
+    pub surname: String,
+}
+
+#[derive(Debug, Clone, Hash, PartialEq, Eq, Serialize, Deserialize)]
+struct Users {
+    pub user: Vec<User>,
+}
+
+#[derive(Debug, Clone, Hash, PartialEq, Eq, Serialize, Deserialize)]
+struct TwoUsers {
+    pub user0: User,
+    pub user1: User,
+}
+
+#[test]
+fn no_unnecessary_newlines_array() {
+    let toml = to_string(&Users {
+        user: vec![
+            User {
+                name: "John".to_string(),
+                surname: "Doe".to_string(),
+            },
+            User {
+                name: "Jane".to_string(),
+                surname: "Dough".to_string(),
+            },
+        ],
+    })
+    .unwrap();
+    assert!(!toml.starts_with('\n'));
+}
+
+#[test]
+fn no_unnecessary_newlines_table() {
+    let toml = to_string(&TwoUsers {
+        user0: User {
+            name: "John".to_string(),
+            surname: "Doe".to_string(),
+        },
+        user1: User {
+            name: "Jane".to_string(),
+            surname: "Dough".to_string(),
+        },
+    })
+    .unwrap();
+    assert!(!toml.starts_with('\n'));
+}