2 files changed, 41 insertions, 17 deletions
diff --git a/Lib/test/test_string/_support.py b/Lib/test/test_string/_support.py
index eaa3354a559..e1d7f6f6500 100644
--- a/Lib/test/test_string/_support.py
+++ b/Lib/test/test_string/_support.py
@@ -1,35 +1,46 @@
-import unittest
 from string.templatelib import Interpolation
 
 
 class TStringBaseCase:
+    def assertInterpolationEqual(self, i, exp):
+        """Test Interpolation equality.
+
+        The *i* argument must be an Interpolation instance.
+
+        The *exp* argument must be a tuple of the form
+        (value, expression, conversion, format_spec) where the final three
+        items may be omitted and are assumed to be '', None and '' respectively.
+        """
+        if len(exp) == 4:
+            actual = (i.value, i.expression, i.conversion, i.format_spec)
+            self.assertEqual(actual, exp)
+        elif len(exp) == 3:
+            self.assertEqual((i.value, i.expression, i.conversion), exp)
+            self.assertEqual(i.format_spec, "")
+        elif len(exp) == 2:
+            self.assertEqual((i.value, i.expression), exp)
+            self.assertEqual(i.conversion, None)
+            self.assertEqual(i.format_spec, "")
+        elif len(exp) == 1:
+            self.assertEqual((i.value,), exp)
+            self.assertEqual(i.expression, "")
+            self.assertEqual(i.conversion, None)
+            self.assertEqual(i.format_spec, "")
+
     def assertTStringEqual(self, t, strings, interpolations):
         """Test template string literal equality.
 
         The *strings* argument must be a tuple of strings equal to *t.strings*.
 
         The *interpolations* argument must be a sequence of tuples which are
-        compared against *t.interpolations*. Each tuple consists of
-        (value, expression, conversion, format_spec), though the final two
-        items may be omitted, and are assumed to be None and '' respectively.
+        compared against *t.interpolations*. Each tuple must match the form
+        described in the `assertInterpolationEqual` method.
         """
         self.assertEqual(t.strings, strings)
         self.assertEqual(len(t.interpolations), len(interpolations))
 
         for i, exp in zip(t.interpolations, interpolations, strict=True):
-            if len(exp) == 4:
-                actual = (i.value, i.expression, i.conversion, i.format_spec)
-                self.assertEqual(actual, exp)
-                continue
-
-            if len(exp) == 3:
-                self.assertEqual((i.value, i.expression, i.conversion), exp)
-                self.assertEqual(i.format_spec, '')
-                continue
-
-            self.assertEqual((i.value, i.expression), exp)
-            self.assertEqual(i.format_spec, '')
-            self.assertIsNone(i.conversion)
+            self.assertInterpolationEqual(i, exp)
 
 
 def convert(value, conversion):
diff --git a/Lib/test/test_string/test_templatelib.py b/Lib/test/test_string/test_templatelib.py
index 85fcff486d6..adaf590e64d 100644
--- a/Lib/test/test_string/test_templatelib.py
+++ b/Lib/test/test_string/test_templatelib.py
@@ -45,6 +45,19 @@ world"""
         self.assertEqual(len(t.interpolations), 0)
         self.assertEqual(fstring(t), 'Hello,\nworld')
 
+    def test_interpolation_creation(self):
+        i = Interpolation('Maria', 'name', 'a', 'fmt')
+        self.assertInterpolationEqual(i, ('Maria', 'name', 'a', 'fmt'))
+
+        i = Interpolation('Maria', 'name', 'a')
+        self.assertInterpolationEqual(i, ('Maria', 'name', 'a'))
+
+        i = Interpolation('Maria', 'name')
+        self.assertInterpolationEqual(i, ('Maria', 'name'))
+
+        i = Interpolation('Maria')
+        self.assertInterpolationEqual(i, ('Maria',))
+
     def test_creation_interleaving(self):
         # Should add strings on either side
         t = Template(Interpolation('Maria', 'name', None, ''))