TST: added test with missing categories for value_counts (#54837)

Author: rsm-23

pandas/tests/frame/methods/test_value_counts.py

@@ -189,3 +189,17 @@ def test_value_counts_categorical_future_warning():
         name="count",
     )
     tm.assert_series_equal(result, expected)
+
+
+def test_value_counts_with_missing_category():
+    # GH-54836
+    df = pd.DataFrame({"a": pd.Categorical([1, 2, 4], categories=[1, 2, 3, 4])})
+    result = df.value_counts()
+    expected = pd.Series(
+        [1, 1, 1, 0],
+        index=pd.MultiIndex.from_arrays(
+            [pd.CategoricalIndex([1, 2, 4, 3], categories=[1, 2, 3, 4], name="a")]
+        ),
+        name="count",
+    )
+    tm.assert_series_equal(result, expected)