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diff --git a/js/src/jit-test/tests/basic/dumpStringRepresentation.js b/js/src/jit-test/tests/basic/dumpStringRepresentation.js
new file mode 100644
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+++ b/js/src/jit-test/tests/basic/dumpStringRepresentation.js
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+// |jit-test| skip-if: typeof dumpStringRepresentation !== 'function'
+
+// Try the dumpStringRepresentation shell function on various types of
+// strings, and make sure it doesn't crash.
+
+print("Empty string:");
+dumpStringRepresentation("");
+
+print("\nResult of coercion to string:");
+dumpStringRepresentation();
+
+print("\nString with an index value:");
+dumpStringRepresentation((12345).toString());
+
+print("\ns = Simple short atom:");
+var s = "xxxxxxxx";
+dumpStringRepresentation(s);
+
+// Simple non-atom flat.
+print("\ns + s: Non-atom flat:");
+var s2 = s + s;
+dumpStringRepresentation(s2);
+
+print("\nNon-Latin1 flat:");
+var j = "渋谷区";
+dumpStringRepresentation(j);
+
+print("\nt = Non-inline atom:");
+var t = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"; // 31 characters
+dumpStringRepresentation(t);
+
+print("\nr1 = t + s: Simple rope:");
+var r1 = t + s;
+dumpStringRepresentation(r1);
+
+// Flatten that rope, and re-examine the representations of both the result and
+// its former leaves. This should be an extensible string.
+print("\nr1, former rope after flattening, now extensible:");
+r1.match(/x/);
+dumpStringRepresentation(r1);
+
+print("\nt, s: Original leaves, representation unchanged:");
+dumpStringRepresentation(t);
+dumpStringRepresentation(s);
+
+// Create a new rope with the extensible string as its left child.
+print("\nr2 = r1 + s: Rope with extensible leftmost child:");
+var r2 = r1 + s;
+dumpStringRepresentation(r2);
+
+// Flatten that; this should re-use the extensible string's buffer.
+print("\nr2: flattened, stole r1's buffer:");
+r2.match(/x/);
+dumpStringRepresentation(r2);
+
+print("\nr1: mutated into a dependent string:");
+dumpStringRepresentation(r1);
+
+print("\nr3 = r2 + s: a new rope with an extensible leftmost child:");
+r3 = r2 + s;
+r3.match(/x/);
+dumpStringRepresentation(r3);
+
+print("\nr2: now mutated into a dependent string");
+dumpStringRepresentation(r2);
+
+print("\nr1: now a doubly-dependent string, because of r2's mutation:");
+dumpStringRepresentation(r1);
+
+print("\nt, s: Original leaves, representation unchanged:");
+dumpStringRepresentation(t);
+dumpStringRepresentation(s);
+
+// Extensible string, created directly.
+print("\nExtensible:");
+var e = newString("一二三四五六七八九*一二三四五六七八", { capacity: 80 });
+dumpStringRepresentation(e);
+
+// Reuse an extensible string's storage when flattening a rope whose DAG contains
+// the extensible string multiple times.
+print("\nFlattened dag with shared leaves:");
+var e_flat = newRope(e, newRope(e, "!"));
+ensureLinearString(e_flat);
+dumpStringRepresentation(e_flat);
+assertEq(e_flat.charAt(e.length), e_flat.charAt(0));
+
+for (var str of representativeStringArray())
+    dumpStringRepresentation(str);