Applied changes according to reviews by @jreback

Author: HyunTruth

doc/source/whatsnew/v0.24.0.txt

@@ -711,7 +711,7 @@ Reshaping
 - Bug in :func:`get_dummies` with Unicode attributes in Python 2 (:issue:`22084`)
 - Bug in :meth:`DataFrame.replace` raises ``RecursionError`` when replacing empty lists (:issue:`22083`)
 - Bug in :meth:`Series.replace` and meth:`DataFrame.replace` when dict is used as the `to_replace` value and one key in the dict is is another key's value, the results were inconsistent between using integer key and using string key (:issue:`20656`)
-- Bug in :meth:`DataFrame.drop_duplicates` for empty DataFrame throws error (:issue:`20516`)
+- Bug in :meth:`DataFrame.drop_duplicates` for empty ``DataFrame`` which incorrectly raises error (:issue:`20516`)
 
 Build Changes
 ^^^^^^^^^^^^^

pandas/tests/frame/test_duplicates.py

@@ -265,9 +265,26 @@ def test_drop_duplicates_tuple():
 
 def test_drop_duplicates_empty():
     # GH 20516
-    df = DataFrame()
-    result = df.drop_duplicates()
-    tm.assert_frame_equal(result, df)
+    expected = DataFrame()
+    result = expected.drop_duplicates()
+    tm.assert_frame_equal(result, expected)
+
+    expected = DataFrame(columns=[])
+    result = expected.drop_duplicates()
+    tm.assert_frame_equal(result, expected)
+
+    expected = DataFrame(columns=['A', 'B', 'C'])
+    result = expected.drop_duplicates()
+    tm.assert_frame_equal(result, expected)
+
+    expected = DataFrame(index=[])
+    result = expected.drop_duplicates()
+    tm.assert_frame_equal(result, expected)
+
+    expected = DataFrame(index=['A', 'B', 'C'])
+    result = expected.drop_duplicates()
+    tm.assert_frame_equal(result, expected)
+
 
 
 def test_drop_duplicates_NA():