diff --git a/Lib/fontTools/misc/testTools.py b/Lib/fontTools/misc/testTools.py
index db316a827..c29d7ca4d 100644
--- a/Lib/fontTools/misc/testTools.py
+++ b/Lib/fontTools/misc/testTools.py
@@ -3,6 +3,7 @@
 from collections.abc import Iterable
 from io import BytesIO
 import os
+import re
 import shutil
 import sys
 import tempfile
@@ -133,6 +134,31 @@ def getXML(func, ttFont=None):
     return xml.splitlines()
 
 
+def stripVariableItemsFromTTX(
+    string: str,
+    ttLibVersion: bool = True,
+    checkSumAdjustment: bool = True,
+    modified: bool = True,
+    created: bool = True,
+    sfntVersion: bool = False,  # opt-in only
+) -> str:
+    """Strip stuff like ttLibVersion, checksums, timestamps, etc. from TTX dumps."""
+    # ttlib changes with the fontTools version
+    if ttLibVersion:
+        string = re.sub(' ttLibVersion="[^"]+"', "", string)
+    # sometimes (e.g. some subsetter tests) we don't care whether it's OTF or TTF
+    if sfntVersion:
+        string = re.sub(' sfntVersion="[^"]+"', "", string)
+    # head table checksum and creation and mod date changes with each save.
+    if checkSumAdjustment:
+        string = re.sub('<checkSumAdjustment value="[^"]+"/>', "", string)
+    if modified:
+        string = re.sub('<modified value="[^"]+"/>', "", string)
+    if created:
+        string = re.sub('<created value="[^"]+"/>', "", string)
+    return string
+
+
 class MockFont(object):
     """A font-like object that automatically adds any looked up glyphname
     to its glyphOrder."""
diff --git a/Tests/fontBuilder/fontBuilder_test.py b/Tests/fontBuilder/fontBuilder_test.py
index 6368cb876..775e94d9a 100644
--- a/Tests/fontBuilder/fontBuilder_test.py
+++ b/Tests/fontBuilder/fontBuilder_test.py
@@ -1,13 +1,13 @@
 
 import os
 import pytest
-import re
 from fontTools.ttLib import TTFont
 from fontTools.pens.ttGlyphPen import TTGlyphPen
 from fontTools.pens.t2CharStringPen import T2CharStringPen
 from fontTools.fontBuilder import FontBuilder
 from fontTools.ttLib.tables.TupleVariation import TupleVariation
 from fontTools.misc.psCharStrings import T2CharString
+from fontTools.misc.testTools import stripVariableItemsFromTTX
 
 
 def getTestData(fileName, mode="r"):
@@ -16,16 +16,6 @@ def getTestData(fileName, mode="r"):
         return f.read()
 
 
-def strip_VariableItems(string):
-    # ttlib changes with the fontTools version
-    string = re.sub(' ttLibVersion=".*"', '', string)
-    # head table checksum and creation and mod date changes with each save.
-    string = re.sub('<checkSumAdjustment value="[^"]+"/>', '', string)
-    string = re.sub('<modified value="[^"]+"/>', '', string)
-    string = re.sub('<created value="[^"]+"/>', '', string)
-    return string
-
-
 def drawTestGlyph(pen):
     pen.moveTo((100, 100))
     pen.lineTo((100, 1000))
@@ -91,8 +81,8 @@ def _verifyOutput(outPath, tables=None):
     f = TTFont(outPath)
     f.saveXML(outPath + ".ttx", tables=tables)
     with open(outPath + ".ttx") as f:
-        testData = strip_VariableItems(f.read())
-    refData = strip_VariableItems(getTestData(os.path.basename(outPath) + ".ttx"))
+        testData = stripVariableItemsFromTTX(f.read())
+    refData = stripVariableItemsFromTTX(getTestData(os.path.basename(outPath) + ".ttx"))
     assert refData == testData
 
 
diff --git a/Tests/subset/data/expect_lcar_0.ttx b/Tests/subset/data/expect_lcar_0.ttx
index feb866d7f..0edcaa111 100644
--- a/Tests/subset/data/expect_lcar_0.ttx
+++ b/Tests/subset/data/expect_lcar_0.ttx
@@ -12,5 +12,5 @@
       </Carets>
     </LigatureCarets>
   </lcar>
-  
+
 </ttFont>
diff --git a/Tests/subset/data/expect_lcar_1.ttx b/Tests/subset/data/expect_lcar_1.ttx
index 26b500823..72b4aabc6 100644
--- a/Tests/subset/data/expect_lcar_1.ttx
+++ b/Tests/subset/data/expect_lcar_1.ttx
@@ -12,5 +12,5 @@
       </Carets>
     </LigatureCarets>
   </lcar>
-  
+
 </ttFont>
diff --git a/Tests/subset/data/expect_opbd_0.ttx b/Tests/subset/data/expect_opbd_0.ttx
index 55842a01c..3f6c41991 100644
--- a/Tests/subset/data/expect_opbd_0.ttx
+++ b/Tests/subset/data/expect_opbd_0.ttx
@@ -14,5 +14,5 @@
       </OpticalBoundsDeltas>
     </OpticalBounds>
   </opbd>
-  
+
 </ttFont>
diff --git a/Tests/subset/data/expect_opbd_1.ttx b/Tests/subset/data/expect_opbd_1.ttx
index 080abd914..7b40401b4 100644
--- a/Tests/subset/data/expect_opbd_1.ttx
+++ b/Tests/subset/data/expect_opbd_1.ttx
@@ -14,5 +14,5 @@
       </OpticalBoundsPoints>
     </OpticalBounds>
   </opbd>
-  
+
 </ttFont>
diff --git a/Tests/subset/data/expect_prop_0.ttx b/Tests/subset/data/expect_prop_0.ttx
index f8ca15093..64201e129 100644
--- a/Tests/subset/data/expect_prop_0.ttx
+++ b/Tests/subset/data/expect_prop_0.ttx
@@ -7,5 +7,5 @@
       <DefaultProperties value="3"/>
     </GlyphProperties>
   </prop>
-  
+
 </ttFont>
diff --git a/Tests/subset/data/expect_prop_1.ttx b/Tests/subset/data/expect_prop_1.ttx
index f7f2d23c6..a582ac21c 100644
--- a/Tests/subset/data/expect_prop_1.ttx
+++ b/Tests/subset/data/expect_prop_1.ttx
@@ -10,5 +10,5 @@
       </Properties>
     </GlyphProperties>
   </prop>
-  
+
 </ttFont>
diff --git a/Tests/subset/subset_test.py b/Tests/subset/subset_test.py
index d195af0fe..dbc410a81 100644
--- a/Tests/subset/subset_test.py
+++ b/Tests/subset/subset_test.py
@@ -1,5 +1,5 @@
 import io
-from fontTools.misc.testTools import getXML
+from fontTools.misc.testTools import getXML, stripVariableItemsFromTTX
 from fontTools.misc.textTools import tobytes, tostr
 from fontTools import subset
 from fontTools.fontBuilder import FontBuilder
@@ -48,15 +48,10 @@ class SubsetTest(unittest.TestCase):
                             "tmp%d%s" % (self.num_tempfiles, suffix))
 
     def read_ttx(self, path):
-        lines = []
-        with open(path, "r", encoding="utf-8") as ttx:
-            for line in ttx.readlines():
-                # Elide ttFont attributes because ttLibVersion may change.
-                if line.startswith("<ttFont "):
-                    lines.append("<ttFont>\n")
-                else:
-                    lines.append(line.rstrip() + "\n")
-        return lines
+        with open(path, "r", encoding="utf-8") as f:
+            ttx = f.read()
+        # don't care whether TTF or OTF, thus strip sfntVersion as well
+        return stripVariableItemsFromTTX(ttx, sfntVersion=True).splitlines(True)
 
     def expect_ttx(self, font, expected_ttx, tables=None):
         path = self.temp_path(suffix=".ttx")
diff --git a/Tests/varLib/instancer/instancer_test.py b/Tests/varLib/instancer/instancer_test.py
index bb2d17585..b9d4ffe9b 100644
--- a/Tests/varLib/instancer/instancer_test.py
+++ b/Tests/varLib/instancer/instancer_test.py
@@ -1,4 +1,5 @@
 from fontTools.misc.fixedTools import floatToFixedToFloat
+from fontTools.misc.testTools import stripVariableItemsFromTTX
 from fontTools.misc.textTools import Tag
 from fontTools import ttLib
 from fontTools import designspaceLib
@@ -1386,10 +1387,6 @@ def test_setMacOverlapFlags():
     assert b.components[0].flags & flagOverlapCompound != 0
 
 
-def _strip_ttLibVersion(string):
-    return re.sub(' ttLibVersion=".*"', "", string)
-
-
 @pytest.fixture
 def varfont2():
     f = ttLib.TTFont(recalcTimestamp=False)
@@ -1412,7 +1409,7 @@ def _dump_ttx(ttFont):
     ttFont2 = ttLib.TTFont(tmp, recalcBBoxes=False, recalcTimestamp=False)
     s = StringIO()
     ttFont2.saveXML(s)
-    return _strip_ttLibVersion(s.getvalue())
+    return stripVariableItemsFromTTX(s.getvalue())
 
 
 def _get_expected_instance_ttx(
@@ -1428,7 +1425,7 @@ def _get_expected_instance_ttx(
         "r",
         encoding="utf-8",
     ) as fp:
-        return _strip_ttLibVersion(fp.read())
+        return stripVariableItemsFromTTX(fp.read())
 
 
 class InstantiateVariableFontTest(object):