Move test_scatter_line_xticks from Series to DataFrame tests

Relocated the `test_scatter_line_xticks` test from `test_series.py` to `test_frame.py` for better alignment with DataFrame-specific functionality. This refactor ensures the test resides in the appropriate context based on its usage and focus.

Author: MartinBraquet

pandas/tests/plotting/frame/test_frame.py

@@ -847,6 +847,20 @@ def test_scatter_on_datetime_time_data(self):
         df["dtime"] = date_range(start="2014-01-01", freq="h", periods=10).time
         df.plot(kind="scatter", x="dtime", y="a")
 
+    def test_scatter_line_xticks(self):
+        # GH#61005
+        datetime_list = [datetime(year=2025, month=1, day=1, hour=n) for n in range(3)]
+        df = DataFrame(columns=["datetime", "y"])
+        for i, n in enumerate(datetime_list):
+            df.loc[len(df)] = [n, i]
+        fig, ax = plt.subplots(2, sharex=True)
+        df.plot.scatter(x="datetime", y="y", ax=ax[0])
+        scatter_xticks = ax[0].get_xticks()
+        df.plot(x="datetime", y="y", ax=ax[1])
+        line_xticks = ax[1].get_xticks()
+        assert scatter_xticks[0] == line_xticks[0]
+        assert scatter_xticks[-1] == line_xticks[-1]
+
     @pytest.mark.parametrize("x, y", [("dates", "vals"), (0, 1)])
     def test_scatterplot_datetime_data(self, x, y):
         # GH 30391

pandas/tests/plotting/test_series.py

@@ -971,17 +971,3 @@ def test_secondary_y_subplot_axis_labels(self):
         s1.plot(ax=ax2)
         assert len(ax.xaxis.get_minor_ticks()) == 0
         assert len(ax.get_xticklabels()) > 0
-
-    def test_scatter_line_xticks(self):
-        # GH#61005
-        datetime_list = [datetime(year=2025, month=1, day=1, hour=n) for n in range(3)]
-        df = DataFrame(columns=["datetime", "y"])
-        for i, n in enumerate(datetime_list):
-            df.loc[len(df)] = [n, i]
-        fig, ax = plt.subplots(2, sharex=True)
-        df.plot.scatter(x="datetime", y="y", ax=ax[0])
-        scatter_xticks = ax[0].get_xticks()
-        df.plot(x="datetime", y="y", ax=ax[1])
-        line_xticks = ax[1].get_xticks()
-        assert scatter_xticks[0] == line_xticks[0]
-        assert scatter_xticks[-1] == line_xticks[-1]