diff --git a/Lib/test/test_textwrap.py b/Lib/test/test_textwrap.py
index bbd0882..bb4a851 100644
--- a/Lib/test/test_textwrap.py
+++ b/Lib/test/test_textwrap.py
@@ -11,7 +11,7 @@
 import unittest
 from test import support
 
-from textwrap import TextWrapper, wrap, fill, dedent
+from textwrap import TextWrapper, wrap, fill, dedent, indent
 
 
 class BaseTestCase(unittest.TestCase):
@@ -594,11 +594,147 @@
         self.assertEqual(expect, dedent(text))
 
 
+# Test textwrap.indent
+class IndentTestCase(unittest.TestCase):
+    # The examples used for tests. If any of these change, the expected
+    # results in the various test cases must also be updated.
+    # The roundtrip cases are separate, because textwrap.dedent doesn't
+    # handle Windows line endings
+    ROUNDTRIP_CASES = (
+      # Basic test case
+      "Hi.\nThis is a test.\nTesting.",
+      # Include a blank line
+      "Hi.\nThis is a test.\n\nTesting.",
+      # Include leading and trailing blank lines
+      "\nHi.\nThis is a test.\nTesting.\n",
+    )
+    CASES = ROUNDTRIP_CASES + (
+      # Use Windows line endings
+      "Hi.\r\nThis is a test.\r\nTesting.\r\n",
+      # Pathological case
+      "\nHi.\r\nThis is a test.\n\r\nTesting.\r\n\n",
+    )
+
+    def test_indent_nomargin_default(self):
+        # indent should do nothing if 'prefix' is empty.
+        for text in self.CASES:
+            self.assertEqual(indent(text, ''), text)
+
+    def test_indent_nomargin_explicit_default(self):
+        # The same as test_indent_nomargin, but explicitly requesting
+        # the default behaviour by passing None as the predicate
+        for text in self.CASES:
+            self.assertEqual(indent(text, '', None), text)
+
+    def test_indent_nomargin_all_lines(self):
+        # The same as test_indent_nomargin, but using the optional
+        # predicate argument
+        predicate = lambda line: True
+        for text in self.CASES:
+            self.assertEqual(indent(text, '', predicate), text)
+
+    def test_indent_no_lines(self):
+        # Explicitly skip indenting any lines
+        predicate = lambda line: False
+        for text in self.CASES:
+            self.assertEqual(indent(text, '    ', predicate), text)
+
+    def test_roundtrip_spaces(self):
+        # A whitespace prefix should roundtrip with dedent
+        for text in self.ROUNDTRIP_CASES:
+            self.assertEqual(dedent(indent(text, '    ')), text)
+
+    def test_roundtrip_tabs(self):
+        # A whitespace prefix should roundtrip with dedent
+        for text in self.ROUNDTRIP_CASES:
+            self.assertEqual(dedent(indent(text, '\t\t')), text)
+
+    def test_roundtrip_mixed(self):
+        # A whitespace prefix should roundtrip with dedent
+        for text in self.ROUNDTRIP_CASES:
+            self.assertEqual(dedent(indent(text, ' \t  \t ')), text)
+
+    def test_indent_default(self):
+        # Test default indenting of lines that are not whitespace only
+        prefix = '  '
+        expected = (
+          # Basic test case
+          "  Hi.\n  This is a test.\n  Testing.",
+          # Include a blank line
+          "  Hi.\n  This is a test.\n\n  Testing.",
+          # Include leading and trailing blank lines
+          "\n  Hi.\n  This is a test.\n  Testing.\n",
+          # Use Windows line endings
+          "  Hi.\r\n  This is a test.\r\n  Testing.\r\n",
+          # Pathological case
+          "\n  Hi.\r\n  This is a test.\n\r\n  Testing.\r\n\n",
+        )
+        for text, expect in zip(self.CASES, expected):
+            self.assertEqual(indent(text, prefix), expect)
+
+    def test_indent_explicit_default(self):
+        # Test default indenting of lines that are not whitespace only
+        prefix = '  '
+        expected = (
+          # Basic test case
+          "  Hi.\n  This is a test.\n  Testing.",
+          # Include a blank line
+          "  Hi.\n  This is a test.\n\n  Testing.",
+          # Include leading and trailing blank lines
+          "\n  Hi.\n  This is a test.\n  Testing.\n",
+          # Use Windows line endings
+          "  Hi.\r\n  This is a test.\r\n  Testing.\r\n",
+          # Pathological case
+          "\n  Hi.\r\n  This is a test.\n\r\n  Testing.\r\n\n",
+        )
+        for text, expect in zip(self.CASES, expected):
+            self.assertEqual(indent(text, prefix, None), expect)
+
+    def test_indent_all_lines(self):
+        # Add 'prefix' to all lines, including whitespace-only ones.
+        prefix = '  '
+        expected = (
+          # Basic test case
+          "  Hi.\n  This is a test.\n  Testing.",
+          # Include a blank line
+          "  Hi.\n  This is a test.\n  \n  Testing.",
+          # Include leading and trailing blank lines
+          "  \n  Hi.\n  This is a test.\n  Testing.\n",
+          # Use Windows line endings
+          "  Hi.\r\n  This is a test.\r\n  Testing.\r\n",
+          # Pathological case
+          "  \n  Hi.\r\n  This is a test.\n  \r\n  Testing.\r\n  \n",
+        )
+        predicate = lambda line: True
+        for text, expect in zip(self.CASES, expected):
+            self.assertEqual(indent(text, prefix, predicate), expect)
+
+    def test_indent_empty_lines(self):
+        # Add 'prefix' solely to whitespace-only lines.
+        prefix = '  '
+        expected = (
+          # Basic test case
+          "Hi.\nThis is a test.\nTesting.",
+          # Include a blank line
+          "Hi.\nThis is a test.\n  \nTesting.",
+          # Include leading and trailing blank lines
+          "  \nHi.\nThis is a test.\nTesting.\n",
+          # Use Windows line endings
+          "Hi.\r\nThis is a test.\r\nTesting.\r\n",
+          # Pathological case
+          "  \nHi.\r\nThis is a test.\n  \r\nTesting.\r\n  \n",
+        )
+        predicate = lambda line: not line.strip()
+        for text, expect in zip(self.CASES, expected):
+            self.assertEqual(indent(text, prefix, predicate), expect)
+
+
 def test_main():
     support.run_unittest(WrapTestCase,
                               LongWordTestCase,
                               IndentTestCases,
-                              DedentTestCase)
+                              DedentTestCase,
+                              IndentTestCase)
 
 if __name__ == '__main__':
     test_main()