Add a simple test for the packaging RECORD file.

The existing test_record is not easily extendable to add script files or
extension modules: it collects all files from fake_dists and generates a
RECORD file at runtime.  I felt more comfortable adding a new test
written from scratch more self-contained (just one project with
well-defined files) and more stupid (the checksums and sizes are
computed once and hard-coded).

Lib/packaging/tests/test_command_install_distinfo.py

@@ -3,10 +3,11 @@
 import os
 import csv
 import hashlib
-import sys
+import sysconfig
 
 from packaging.command.install_distinfo import install_distinfo
 from packaging.command.cmd import Command
+from packaging.compiler.extension import Extension
 from packaging.metadata import Metadata
 from packaging.tests import unittest, support
 
@@ -121,6 +122,57 @@ class InstallDistinfoTestCase(support.TempdirManager,
         self.checkLists(os.listdir(dist_info),
                         ['METADATA', 'REQUESTED', 'INSTALLER'])
 
+    def test_record_basic(self):
+        install_dir = self.mkdtemp()
+        modules_dest = os.path.join(install_dir, 'lib')
+        scripts_dest = os.path.join(install_dir, 'bin')
+        project_dir, dist = self.create_dist(
+            name='Spamlib', version='0.1',
+            py_modules=['spam'], scripts=['spamd'],
+            ext_modules=[Extension('_speedspam', ['_speedspam.c'])])
+
+        # using a real install_dist command is too painful, so we use a mock
+        # class that's only a holder for options to be used by install_distinfo
+        # and we create placeholder files manually instead of using build_*.
+        # the install_* commands will still be consulted by install_distinfo.
+        os.chdir(project_dir)
+        self.write_file('spam', '# Python module')
+        self.write_file('spamd', '# Python script')
+        extmod = '_speedspam%s' % sysconfig.get_config_var('SO')
+        self.write_file(extmod, '')
+
+        install = DummyInstallCmd(dist)
+        install.outputs = ['spam', 'spamd', extmod]
+        install.install_lib = modules_dest
+        install.install_scripts = scripts_dest
+        dist.command_obj['install_dist'] = install
+
+        cmd = install_distinfo(dist)
+        cmd.ensure_finalized()
+        dist.command_obj['install_distinfo'] = cmd
+        cmd.run()
+
+        record = os.path.join(modules_dest, 'Spamlib-0.1.dist-info', 'RECORD')
+        with open(record, encoding='utf-8') as fp:
+            content = fp.read()
+
+        found = []
+        for line in content.splitlines():
+            filename, checksum, size = line.split(',')
+            filename = os.path.basename(filename)
+            found.append((filename, checksum, size))
+
+        expected = [
+            ('spam', '6ab2f288ef2545868effe68757448b45', '15'),
+            ('spamd','d13e6156ce78919a981e424b2fdcd974', '15'),
+            (extmod, 'd41d8cd98f00b204e9800998ecf8427e', '0'),
+            ('METADATA', '846de67e49c3b92c81fb1ebd7bc07046', '172'),
+            ('INSTALLER', '44e3fde05f3f537ed85831969acf396d', '9'),
+            ('REQUESTED', 'd41d8cd98f00b204e9800998ecf8427e', '0'),
+            ('RECORD', '', ''),
+        ]
+        self.assertEqual(found, expected)
+
     def test_record(self):
         pkg_dir, dist = self.create_dist(name='foo',
                                          version='1.0')