Issue #19990: Added tests for the imghdr module.

Based on patch by Claudiu Popa.

Lib/test/imghdrdata/python.pbm

@@ -0,0 +1,3 @@
+P4
+16 16
+ûñ¿úßÕ­±[ñ¥a_ÁX
°
°
ðððð?ÿÿ

Lib/test/imghdrdata/python.xbm

@@ -0,0 +1,6 @@
+#define python_width 16
+#define python_height 16
+static char python_bits[] = {
+  0xDF, 0xFE, 0x8F, 0xFD, 0x5F, 0xFB, 0xAB, 0xFE, 0xB5, 0x8D, 0xDA, 0x8F, 
+  0xA5, 0x86, 0xFA, 0x83, 0x1A, 0x80, 0x0D, 0x80, 0x0D, 0x80, 0x0F, 0xE0, 
+  0x0F, 0xF8, 0x0F, 0xF8, 0x0F, 0xFC, 0xFF, 0xFF, };

Lib/test/test_imghdr.py

@@ -0,0 +1,131 @@
+import imghdr
+import io
+import os
+import unittest
+import warnings
+from test.support import findfile, TESTFN, unlink
+
+TEST_FILES = (
+    ('python.png', 'png'),
+    ('python.gif', 'gif'),
+    ('python.bmp', 'bmp'),
+    ('python.ppm', 'ppm'),
+    ('python.pgm', 'pgm'),
+    ('python.pbm', 'pbm'),
+    ('python.jpg', 'jpeg'),
+    ('python.ras', 'rast'),
+    ('python.sgi', 'rgb'),
+    ('python.tiff', 'tiff'),
+    ('python.xbm', 'xbm')
+)
+
+class UnseekableIO(io.FileIO):
+    def tell(self):
+        raise io.UnsupportedOperation
+
+    def seek(self, *args, **kwargs):
+        raise io.UnsupportedOperation
+
+class TestImghdr(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.testfile = findfile('python.png', subdir='imghdrdata')
+        with open(cls.testfile, 'rb') as stream:
+            cls.testdata = stream.read()
+
+    def tearDown(self):
+        unlink(TESTFN)
+
+    def test_data(self):
+        for filename, expected in TEST_FILES:
+            filename = findfile(filename, subdir='imghdrdata')
+            self.assertEqual(imghdr.what(filename), expected)
+            with open(filename, 'rb') as stream:
+                self.assertEqual(imghdr.what(stream), expected)
+            with open(filename, 'rb') as stream:
+                data = stream.read()
+            self.assertEqual(imghdr.what(None, data), expected)
+            self.assertEqual(imghdr.what(None, bytearray(data)), expected)
+
+    def test_register_test(self):
+        def test_jumbo(h, file):
+            if h.startswith(b'eggs'):
+                return 'ham'
+        imghdr.tests.append(test_jumbo)
+        self.addCleanup(imghdr.tests.pop)
+        self.assertEqual(imghdr.what(None, b'eggs'), 'ham')
+
+    def test_file_pos(self):
+        with open(TESTFN, 'wb') as stream:
+            stream.write(b'ababagalamaga')
+            pos = stream.tell()
+            stream.write(self.testdata)
+        with open(TESTFN, 'rb') as stream:
+            stream.seek(pos)
+            self.assertEqual(imghdr.what(stream), 'png')
+            self.assertEqual(stream.tell(), pos)
+
+    def test_bad_args(self):
+        with self.assertRaises(TypeError):
+            imghdr.what()
+        with self.assertRaises(AttributeError):
+            imghdr.what(None)
+        with self.assertRaises(TypeError):
+            imghdr.what(self.testfile, 1)
+        with self.assertRaises(AttributeError):
+            imghdr.what(os.fsencode(self.testfile))
+        with open(self.testfile, 'rb') as f:
+            with self.assertRaises(AttributeError):
+                imghdr.what(f.fileno())
+
+    def test_invalid_headers(self):
+        for header in (b'\211PN\r\n',
+                       b'\001\331',
+                       b'\x59\xA6',
+                       b'cutecat',
+                       b'000000JFI',
+                       b'GIF80'):
+            self.assertIsNone(imghdr.what(None, header))
+
+    def test_string_data(self):
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", BytesWarning)
+            for filename, _ in TEST_FILES:
+                filename = findfile(filename, subdir='imghdrdata')
+                with open(filename, 'rb') as stream:
+                    data = stream.read().decode('latin1')
+                with self.assertRaises(TypeError):
+                    imghdr.what(io.StringIO(data))
+                with self.assertRaises(TypeError):
+                    imghdr.what(None, data)
+
+    def test_missing_file(self):
+        with self.assertRaises(FileNotFoundError):
+            imghdr.what('missing')
+
+    def test_closed_file(self):
+        stream = open(self.testfile, 'rb')
+        stream.close()
+        with self.assertRaises(ValueError) as cm:
+            imghdr.what(stream)
+        stream = io.BytesIO(self.testdata)
+        stream.close()
+        with self.assertRaises(ValueError) as cm:
+            imghdr.what(stream)
+
+    def test_unseekable(self):
+        with open(TESTFN, 'wb') as stream:
+            stream.write(self.testdata)
+        with UnseekableIO(TESTFN, 'rb') as stream:
+            with self.assertRaises(io.UnsupportedOperation):
+                imghdr.what(stream)
+
+    def test_output_stream(self):
+        with open(TESTFN, 'wb') as stream:
+            stream.write(self.testdata)
+            stream.seek(0)
+            with self.assertRaises(OSError) as cm:
+                imghdr.what(stream)
+
+if __name__ == '__main__':
+    unittest.main()

Lib/test/test_sundry.py

@@ -42,7 +42,6 @@ class TestUntestedModules(unittest.TestCase):
             import encodings
             import formatter
             import html.entities
-            import imghdr
             import keyword
             import mailcap
             import nturl2path

Misc/NEWS

@@ -292,6 +292,9 @@ IDLE
 Tests
 -----
 
+- Issue #19990: Added tests for the imghdr module.  Based on patch by
+  Claudiu Popa.
+
 - Issue #19804: The test_find_mac test in test_uuid is now skipped if the
   ifconfig executable is not available.