1 files changed, 55 insertions, 0 deletions

diff --git a/crates/libeditor/src/extend_selection.rs b/crates/libeditor/src/extend_selection.rs
index 154f89671..30cff6558 100644
--- a/crates/libeditor/src/extend_selection.rs
+++ b/crates/libeditor/src/extend_selection.rs
@@ -64,3 +64,58 @@ fn adj_comments(node: SyntaxNodeRef, dir: Direction) -> SyntaxNodeRef {
     }
     res
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use test_utils::extract_offset;
+
+    fn do_check(before: &str, afters: &[&str]) {
+        let (cursor, before) = extract_offset(before);
+        let file = File::parse(&before);
+        let mut range = TextRange::offset_len(cursor, 0.into());
+        for &after in afters {
+            range = extend_selection(&file, range)
+                .unwrap();
+            let actual = &before[range];
+            assert_eq!(after, actual);
+        }
+    }
+
+    #[test]
+    fn test_extend_selection_arith() {
+        do_check(
+            r#"fn foo() { <|>1 + 1 }"#,
+            &["1", "1 + 1", "{ 1 + 1 }"],
+        );
+    }
+
+    #[test]
+    fn test_extend_selection_start_of_the_lind() {
+        do_check(
+            r#"
+impl S {
+<|>    fn foo() {
+
+    }
+}"#,
+            &["fn foo() {\n\n    }"]
+        );
+    }
+
+    #[test]
+    fn test_extend_selection_comments() {
+        do_check(
+            r#"
+fn bar(){}
+
+// fn foo() {
+// 1 + <|>1
+// }
+
+// fn foo(){}
+    "#,
+            &["// 1 + 1", "// fn foo() {\n// 1 + 1\n// }"]
+        );
+    }
+}