Add missing test for use completions

crates/ide_completion/src/tests/use_tree.rs

@@ -31,6 +31,25 @@ mod foo {}
     );
 }
 
+#[test]
+fn use_tree_start_abs() {
+    cov_mark::check!(use_tree_crate_roots_only);
+    check(
+        r#"
+//- /lib.rs crate:main deps:other_crate
+use ::f$0
+
+struct Foo;
+mod foo {}
+//- /other_crate/lib.rs crate:other_crate
+// nothing here
+"#,
+        expect![[r#"
+            md other_crate
+        "#]],
+    );
+}
+
 #[test]
 fn dont_complete_current_use() {
     cov_mark::check!(dont_complete_current_use);