Added smoke test for Axes.stem (matplotlib#27135)

* Added smoke test for Axes.stem

* Updates to include bottom and orientation

* Move code to stem function

* Remove whitespace

* Changed dates

* Formatting Fixes

Author: 0taj

lib/matplotlib/tests/test_datetime.py

@@ -591,11 +591,33 @@ def test_stairs(self):
         fig, ax = plt.subplots()
         ax.stairs(...)
 
-    @pytest.mark.xfail(reason="Test for stem not written yet")
     @mpl.style.context("default")
     def test_stem(self):
-        fig, ax = plt.subplots()
-        ax.stem(...)
+        mpl.rcParams["date.converter"] = "concise"
+
+        fig, (ax1, ax2, ax3, ax4, ax5, ax6) = plt.subplots(6, 1, layout="constrained")
+
+        limit_value = 10
+        above = datetime.datetime(2023, 9, 18)
+        below = datetime.datetime(2023, 11, 18)
+
+        x_ranges = np.arange(1, limit_value)
+        y_ranges = np.arange(1, limit_value)
+
+        x_dates = np.array(
+            [datetime.datetime(2023, 10, n) for n in range(1, limit_value)]
+        )
+        y_dates = np.array(
+            [datetime.datetime(2023, 10, n) for n in range(1, limit_value)]
+        )
+
+        ax1.stem(x_dates, y_dates, bottom=above)
+        ax2.stem(x_dates, y_ranges, bottom=5)
+        ax3.stem(x_ranges, y_dates, bottom=below)
+
+        ax4.stem(x_ranges, y_dates, orientation="horizontal", bottom=above)
+        ax5.stem(x_dates, y_ranges, orientation="horizontal", bottom=5)
+        ax6.stem(x_ranges, y_dates, orientation="horizontal", bottom=below)
 
     @mpl.style.context("default")
     def test_step(self):