chore(lint): add test case for #15990

Author: xuanduc987

crates/oxc_linter/src/rules/eslint/sort_imports.rs

@@ -465,13 +465,14 @@ fn get_number_of_lines_between(left: Span, right: Span, ctx: &LintContext) -> us
         return 0;
     }
     let between_span = Span::new(left.end, right.start);
-    let count = ctx.source_range(between_span).chars().filter(|c| *c == '\n').count();
+    let count = ctx.source_range(between_span).lines().count();
 
     if count < 1 {
         return 0;
     }
 
-    // In different lines, need to subtract 2 because the count includes the first and last line.
+    // In different lines, need to subtract 1, because we need new line 2 time to have 1 line
+    // between node
     count - 1
 }
 
@@ -580,6 +581,13 @@ fn test() {
         (
             "import b from 'b';
 
+            import a from 'a';",
+            Some(serde_json::json!([{ "allowSeparatedGroups": true }])),
+        ),
+        // No leading whitespaces - issue #15990
+        (
+            "import b from 'b';
+
 import a from 'a';",
             Some(serde_json::json!([{ "allowSeparatedGroups": true }])),
         ),