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diff --git a/js/src/tests/test262/built-ins/TypedArray/prototype/join/BigInt/detached-buffer-during-fromIndex-returns-single-comma.js b/js/src/tests/test262/built-ins/TypedArray/prototype/join/BigInt/detached-buffer-during-fromIndex-returns-single-comma.js
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+// Copyright (C) 2020 Rick Waldron. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-%typedarray%.prototype.join
+description: Returns single separator if buffer is detached after ValidateTypedArray
+info: |
+  %TypedArray%.prototype.join ( separator )
+
+  The interpretation and use of the arguments of %TypedArray%.prototype.join are the same as for Array.prototype.join as defined in 22.1.3.15.
+
+  When the join method is called with one argument separator, the following steps are taken:
+
+  Let O be the this value.
+  Perform ? ValidateTypedArray(O).
+  Let len be O.[[ArrayLength]].
+  If separator is undefined, let sep be the single-element String ",".
+  Else, let sep be ? ToString(separator).
+  Let R be the empty String.
+  Let k be 0.
+  Repeat, while k < len,
+    If k > 0, set R to the string-concatenation of R and sep.
+    Let element be ! Get(O, ! ToString(𝔽(k))).
+    If element is undefined or null, let next be the empty String; otherwise, let next be ! ToString(element).
+    Set R to the string-concatenation of R and next.
+    Set k to k + 1.
+  Return R.
+
+includes: [testBigIntTypedArray.js, detachArrayBuffer.js]
+features: [align-detached-buffer-semantics-with-web-reality, BigInt, TypedArray]
+---*/
+
+testWithBigIntTypedArrayConstructors(function(TA) {
+  const sample = new TA([1n,2n,3n]);
+  const separator = {
+    toString() {
+      $DETACHBUFFER(sample.buffer);
+      return ',';
+    }
+  };
+
+  assert.sameValue(sample.join(separator), ',,');
+});
+
+reportCompare(0, 0);