Add a test for 'meson introspect --targets|--target-files'

v2:
Use asssertCountEqual for list comparison ignoring order

run_unittests.py

@@ -2372,6 +2372,38 @@ int main(int argc, char **argv) {
                 self.init(testdir, ['--cross-file=' + name], inprocess=True)
                 self.wipe()
 
+    def test_introspect_target_files(self):
+        '''
+        Tests that mesonintrospect --target-files returns expected output.
+        '''
+        testdir = os.path.join(self.common_test_dir, '8 install')
+        self.init(testdir)
+        expected = {
+            'stat@sta': ['stat.c'],
+            'prog@exe': ['prog.c'],
+        }
+        t_intro = self.introspect('--targets')
+        self.assertCountEqual([t['id'] for t in t_intro], expected)
+        for t in t_intro:
+            id = t['id']
+            tf_intro = self.introspect(['--target-files', id])
+            self.assertEqual(tf_intro, expected[id])
+        self.wipe()
+
+        testdir = os.path.join(self.common_test_dir, '53 custom target')
+        self.init(testdir)
+        expected = {
+            'bindat@cus': ['data_source.txt'],
+            'depfile@cus': [],
+        }
+        t_intro = self.introspect('--targets')
+        self.assertCountEqual([t['id'] for t in t_intro], expected)
+        for t in t_intro:
+            id = t['id']
+            tf_intro = self.introspect(['--target-files', id])
+            self.assertEqual(tf_intro, expected[id])
+        self.wipe()
+
     def test_compiler_run_command(self):
         '''
         The test checks that the compiler object can be passed to