test: add tests for openToDate with showTimeSelectOnly

Added tests to verify that openToDate can be used to specify the default
date when showTimeSelectOnly is true and selected is null. This documents
the existing behavior that addresses the feature request in #6032.

Tests added:
- openToDate as base date with showTimeSelectOnly and null selected
- Current date fallback when neither selected nor openToDate provided
- openToDate with showTimeInput and null selected

Closes #6032

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: martijnrusschen

src/test/show_time_test.test.tsx

@@ -185,4 +185,109 @@ describe("DatePicker", () => {
       expect(onChange).toHaveBeenCalledWith(expectedDate);
     });
   });
+
+  describe("Time Select Only with openToDate", () => {
+    it("should use openToDate as the base date when selecting time with showTimeSelectOnly and selected is null", () => {
+      const onChange = jest.fn();
+      const openToDate = new Date("2025-11-01T00:00:00");
+
+      const { container } = render(
+        <DatePicker
+          selected={null}
+          openToDate={openToDate}
+          onChange={onChange}
+          showTimeSelect
+          showTimeSelectOnly
+        />,
+      );
+
+      const input = safeQuerySelector(container, "input");
+      fireEvent.click(input);
+
+      // Find and click a time option (e.g., 09:00)
+      const timeListItems = container.querySelectorAll(
+        ".react-datepicker__time-list-item",
+      );
+      expect(timeListItems.length).toBeGreaterThan(0);
+
+      // Click on a time option
+      fireEvent.click(timeListItems[0]!);
+
+      expect(onChange).toHaveBeenCalled();
+      const selectedDate = onChange.mock.calls[0][0] as Date;
+
+      // Verify the date part comes from openToDate
+      expect(selectedDate.getFullYear()).toBe(2025);
+      expect(selectedDate.getMonth()).toBe(10); // November is month 10 (0-indexed)
+      expect(selectedDate.getDate()).toBe(1);
+    });
+
+    it("should use current date when showTimeSelectOnly is true and neither selected nor openToDate is provided", () => {
+      const onChange = jest.fn();
+      const today = new Date();
+
+      const { container } = render(
+        <DatePicker
+          selected={null}
+          onChange={onChange}
+          showTimeSelect
+          showTimeSelectOnly
+        />,
+      );
+
+      const input = safeQuerySelector(container, "input");
+      fireEvent.click(input);
+
+      const timeListItems = container.querySelectorAll(
+        ".react-datepicker__time-list-item",
+      );
+      expect(timeListItems.length).toBeGreaterThan(0);
+
+      fireEvent.click(timeListItems[0]!);
+
+      expect(onChange).toHaveBeenCalled();
+      const selectedDate = onChange.mock.calls[0][0] as Date;
+
+      // Verify the date part comes from today
+      expect(selectedDate.getFullYear()).toBe(today.getFullYear());
+      expect(selectedDate.getMonth()).toBe(today.getMonth());
+      expect(selectedDate.getDate()).toBe(today.getDate());
+    });
+
+    it("should use openToDate for showTimeInput when selected is null", () => {
+      const onChange = jest.fn();
+      const openToDate = new Date("2025-11-01T00:00:00");
+
+      const { container } = render(
+        <DatePicker
+          selected={null}
+          openToDate={openToDate}
+          onChange={onChange}
+          showTimeInput
+        />,
+      );
+
+      const input = safeQuerySelector(container, "input");
+      fireEvent.focus(input);
+
+      const timeInput = safeQuerySelector<HTMLInputElement>(
+        container,
+        'input[type="time"].react-datepicker-time__input',
+      );
+
+      fireEvent.change(timeInput, {
+        target: { value: "14:30" },
+      });
+
+      expect(onChange).toHaveBeenCalled();
+      const selectedDate = onChange.mock.calls[0][0] as Date;
+
+      // Verify the date part comes from openToDate
+      expect(selectedDate.getFullYear()).toBe(2025);
+      expect(selectedDate.getMonth()).toBe(10); // November
+      expect(selectedDate.getDate()).toBe(1);
+      expect(selectedDate.getHours()).toBe(14);
+      expect(selectedDate.getMinutes()).toBe(30);
+    });
+  });
 });