Add scaleUpem_test

Tests/ttLib/scaleUpem_test.py

@@ -0,0 +1,68 @@
+from fontTools.ttLib import TTFont
+from fontTools.ttLib.scaleUpem import scale_upem
+import difflib
+import os
+import shutil
+import sys
+import tempfile
+import unittest
+import pytest
+
+class ScaleUpemTest(unittest.TestCase):
+
+    def setUp(self):
+        self.tempdir = None
+        self.num_tempfiles = 0
+
+    def tearDown(self):
+        if self.tempdir:
+            shutil.rmtree(self.tempdir)
+
+    @staticmethod
+    def get_path(test_file_or_folder):
+        parent_dir = os.path.dirname(__file__)
+        return os.path.join(parent_dir, "data", test_file_or_folder)
+
+    def temp_path(self, suffix):
+        self.temp_dir()
+        self.num_tempfiles += 1
+        return os.path.join(self.tempdir,
+                            "tmp%d%s" % (self.num_tempfiles, suffix))
+
+    def temp_dir(self):
+        if not self.tempdir:
+            self.tempdir = tempfile.mkdtemp()
+
+    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
+
+    def expect_ttx(self, font, expected_ttx, tables):
+        path = self.temp_path(suffix=".ttx")
+        font.saveXML(path, tables=tables)
+        actual = self.read_ttx(path)
+        expected = self.read_ttx(expected_ttx)
+        if actual != expected:
+            for line in difflib.unified_diff(
+                    expected, actual, fromfile=expected_ttx, tofile=path):
+                sys.stdout.write(line)
+            self.fail("TTX output is different from expected")
+
+    def test_scale_upem(self):
+
+        font = TTFont(self.get_path("I.ttf"))
+        tables = [table_tag for table_tag in font.keys() if table_tag != "head"]
+
+        scale_upem(font, 512)
+
+        expected_ttx_path = self.get_path("I-512upem.ttx")
+        self.expect_ttx(font, expected_ttx_path, tables)
+
+