diff --git a/memory/gtest/TestJemalloc.cpp b/memory/gtest/TestJemalloc.cpp
deleted file mode 100644
index f37c57376a794..0000000000000
--- a/memory/gtest/TestJemalloc.cpp
+++ /dev/null
@@ -1,51 +0,0 @@
-/* -*-  Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "mozilla/mozalloc.h"
-#include "mozmemory.h"
-
-#include "gtest/gtest.h"
-
-static inline void
-TestOne(size_t size)
-{
-    size_t req = size;
-    size_t adv = malloc_good_size(req);
-    char* p = (char*)malloc(req);
-    size_t usable = moz_malloc_usable_size(p);
-    // NB: Using EXPECT here so that we still free the memory on failure.
-    EXPECT_EQ(adv, usable) <<
-           "malloc_good_size(" << req << ") --> " << adv << "; "
-           "malloc_usable_size(" << req << ") --> " << usable;
-    free(p);
-}
-
-static inline void
-TestThree(size_t size)
-{
-    ASSERT_NO_FATAL_FAILURE(TestOne(size - 1));
-    ASSERT_NO_FATAL_FAILURE(TestOne(size));
-    ASSERT_NO_FATAL_FAILURE(TestOne(size + 1));
-}
-
-TEST(Jemalloc, UsableSizeInAdvance)
-{
-  #define K   * 1024
-  #define M   * 1024 * 1024
-
-  /*
-   * Test every size up to a certain point, then (N-1, N, N+1) triplets for a
-   * various sizes beyond that.
-   */
-
-  for (size_t n = 0; n < 16 K; n++)
-    ASSERT_NO_FATAL_FAILURE(TestOne(n));
-
-  for (size_t n = 16 K; n < 1 M; n += 4 K)
-    ASSERT_NO_FATAL_FAILURE(TestThree(n));
-
-  for (size_t n = 1 M; n < 8 M; n += 128 K)
-    ASSERT_NO_FATAL_FAILURE(TestThree(n));
-}
diff --git a/memory/gtest/moz.build b/memory/gtest/moz.build
deleted file mode 100644
index 8d50ee4e39905..0000000000000
--- a/memory/gtest/moz.build
+++ /dev/null
@@ -1,11 +0,0 @@
-# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
-# vim: set filetype=python:
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-UNIFIED_SOURCES += [
-    'TestJemalloc.cpp',
-]
-
-FINAL_LIBRARY = 'xul-gtest'
diff --git a/memory/moz.build b/memory/moz.build
index 538655c90992d..ea74b1609e834 100644
--- a/memory/moz.build
+++ b/memory/moz.build
@@ -15,7 +15,6 @@ if not CONFIG['JS_STANDALONE']:
 if CONFIG['MOZ_MEMORY']:
     DIRS += [
         'build',
-        'gtest',
         'mozjemalloc',
     ]
 
diff --git a/testing/cppunittest.ini b/testing/cppunittest.ini
index e8026be351cd1..0b74bd55d7467 100644
--- a/testing/cppunittest.ini
+++ b/testing/cppunittest.ini
@@ -31,6 +31,7 @@ skip-if = os != 'win'
 [TestIntegerRange]
 [TestIsCertBuiltInRoot]
 [TestJSONWriter]
+[TestJemalloc]
 [TestLinkedList]
 [TestMacroArgs]
 [TestMacroForEach]
diff --git a/xpcom/tests/TestJemalloc.cpp b/xpcom/tests/TestJemalloc.cpp
new file mode 100644
index 0000000000000..6e14bea4bc9be
--- /dev/null
+++ b/xpcom/tests/TestJemalloc.cpp
@@ -0,0 +1,78 @@
+/* -*-  Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Ideally, this test would be in memory/test/.  But I couldn't get it to build
+ * there (couldn't find TestHarness.h).  I think memory/ is processed too early
+ * in the build.  So it's here.
+ */
+
+#include "TestHarness.h"
+#include "mozmemory.h"
+
+static inline bool
+TestOne(size_t size)
+{
+    size_t req = size;
+    size_t adv = malloc_good_size(req);
+    char* p = (char*)malloc(req);
+    size_t usable = moz_malloc_usable_size(p);
+    if (adv != usable) {
+      fail("malloc_good_size(%d) --> %d; "
+           "malloc_usable_size(%d) --> %d",
+           req, adv, req, usable);
+      return false;
+    }
+    free(p);
+    return true;
+}
+
+static inline bool
+TestThree(size_t size)
+{
+    return TestOne(size - 1) && TestOne(size) && TestOne(size + 1);
+}
+
+static nsresult
+TestJemallocUsableSizeInAdvance()
+{
+  #define K   * 1024
+  #define M   * 1024 * 1024
+
+  /*
+   * Test every size up to a certain point, then (N-1, N, N+1) triplets for a
+   * various sizes beyond that.
+   */
+
+  for (size_t n = 0; n < 16 K; n++)
+    if (!TestOne(n))
+      return NS_ERROR_UNEXPECTED;
+
+  for (size_t n = 16 K; n < 1 M; n += 4 K)
+    if (!TestThree(n))
+      return NS_ERROR_UNEXPECTED;
+
+  for (size_t n = 1 M; n < 8 M; n += 128 K)
+    if (!TestThree(n))
+      return NS_ERROR_UNEXPECTED;
+
+  passed("malloc_good_size");
+
+  return NS_OK;
+}
+
+int main(int argc, char** argv)
+{
+  int rv = 0;
+  ScopedXPCOM xpcom("jemalloc");
+  if (xpcom.failed())
+      return 1;
+
+  if (NS_FAILED(TestJemallocUsableSizeInAdvance()))
+    rv = 1;
+
+  return rv;
+}
+
diff --git a/xpcom/tests/moz.build b/xpcom/tests/moz.build
index 8eb071a5990c5..86e380a32a9f8 100644
--- a/xpcom/tests/moz.build
+++ b/xpcom/tests/moz.build
@@ -45,6 +45,11 @@ if CONFIG['WRAP_STL_INCLUDES'] and not CONFIG['CLANG_CL']:
 
 XPCSHELL_TESTS_MANIFESTS += ['unit/xpcshell.ini']
 
+if CONFIG['MOZ_MEMORY']:
+    GeckoCppUnitTests([
+        'TestJemalloc',
+    ])
+
 # FIXME: bug 577500 TestStaticAtoms fails when run in dist/bin
 #CPP_UNIT_TESTS += [
 #    'TestStaticAtoms',