Add test_fill in test_datetime.py (matplotlib#27401)

* added a test for fill in test_datetime.py

* Removed saving the picture from test code.

* reverted .gitignore changes

I had added my virtual environment to gitignore and pushed it. Reverted back before pull request

* added seed

Author: nidaa-7

lib/matplotlib/tests/test_datetime.py

@@ -284,11 +284,32 @@ def test_eventplot(self):
         fig, ax = plt.subplots()
         ax.eventplot(...)
 
-    @pytest.mark.xfail(reason="Test for fill not written yet")
     @mpl.style.context("default")
     def test_fill(self):
-        fig, ax = plt.subplots()
-        ax.fill(...)
+        mpl.rcParams["date.converter"] = "concise"
+        fig, (ax1, ax2, ax3, ax4) = plt.subplots(4, 1, layout="constrained")
+
+        np.random.seed(19680801)
+
+        x_base_date = datetime.datetime(2023, 1, 1)
+        x_dates = [x_base_date]
+        for _ in range(1, 5):
+            x_base_date += datetime.timedelta(days=np.random.randint(1, 5))
+            x_dates.append(x_base_date)
+
+        y_base_date = datetime.datetime(2023, 1, 1)
+        y_dates = [y_base_date]
+        for _ in range(1, 5):
+            y_base_date += datetime.timedelta(days=np.random.randint(1, 5))
+            y_dates.append(y_base_date)
+
+        x_values = np.random.rand(5) * 5
+        y_values = np.random.rand(5) * 5 - 2
+
+        ax1.fill(x_dates, y_values)
+        ax2.fill(x_values, y_dates)
+        ax3.fill(x_values, y_values)
+        ax4.fill(x_dates, y_dates)
 
     @pytest.mark.xfail(reason="Test for fill_between not written yet")
     @mpl.style.context("default")