1 files changed, 20 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/warp/string-substring-static-strings.js b/js/src/jit-test/tests/warp/string-substring-static-strings.js
new file mode 100644
index 0000000000..1ea8e36c31
--- /dev/null
+++ b/js/src/jit-test/tests/warp/string-substring-static-strings.js
@@ -0,0 +1,20 @@
+// `str.substring(...)` can return static strings.
+
+const strings = [
+  "abcdef",
+  "ABCDEF",
+];
+
+for (let i = 0; i < 500; ++i) {
+  let str = strings[i & 1];
+
+  for (let j = 0; j < 2; ++j) {
+    // One element static string.
+    let r = str.substring(j, j + 1);
+    assertEq(r, str.charAt(j));
+
+    // Two elements static string.
+    let s = str.substring(j, j + 2);
+    assertEq(s, str.charAt(j) + str.charAt(j + 1));
+  }
+}