From a99f698b1e72f96211497a3406fe69f49763697c Mon Sep 17 00:00:00 2001
From: samchan2022 <samchan.goo.123@gmail.com>
Date: Tue, 14 Nov 2023 22:48:35 +0000
Subject: [PATCH] add test_axlines

---
 lib/matplotlib/tests/test_datetime.py | 34 ++++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

diff --git a/lib/matplotlib/tests/test_datetime.py b/lib/matplotlib/tests/test_datetime.py
index b19124a1b764..f57a07348749 100644
--- a/lib/matplotlib/tests/test_datetime.py
+++ b/lib/matplotlib/tests/test_datetime.py
@@ -5,6 +5,7 @@
 
 import matplotlib.pyplot as plt
 import matplotlib as mpl
+from matplotlib.dates import date2num, DateFormatter
 
 
 class TestDatetimePlotting:
@@ -77,11 +78,38 @@ def test_axhspan(self):
         ax3.set_xlabel('Date')
         ax3.set_ylabel('Date')
 
-    @pytest.mark.xfail(reason="Test for axline not written yet")
     @mpl.style.context("default")
     def test_axline(self):
-        fig, ax = plt.subplots()
-        ax.axline(...)
+        mpl.rcParams["date.converter"] = 'concise'
+        fig, (ax1, ax2, ax3) = plt.subplots(3, 1,
+                                            constrained_layout=True,
+                                            figsize=(10, 12))
+
+        start_date = datetime.datetime(2023, 1, 1)
+        dates = [start_date + datetime.timedelta(days=i) for i in range(31)]
+        values = list(range(1, 32))
+
+        ax1.plot(dates, values, 'ro')
+        ax1.axline((date2num(dates[0]), values[0]), (date2num(dates[-1]), values[-1]),
+                   color='blue', linewidth=2)
+        ax1.set_title('Datetime vs. Number')
+        date_format = DateFormatter('%b%d')
+        ax1.xaxis.set_major_formatter(date_format)
+
+        ax2.plot(values, dates, 'ro')
+        ax2.axline((values[0], date2num(dates[0])), (values[-1], date2num(dates[-1])),
+                   color='blue', linewidth=2)
+        ax2.set_title('Number vs. Datetime')
+        ax2.yaxis.set_major_formatter(date_format)
+
+        dates2 = [start_date + datetime.timedelta(days=2*i) for i in range(31)]
+        ax3.plot(dates, dates2, 'ro')
+        ax3.axline((date2num(dates[0]), date2num(dates2[0])),
+                   (date2num(dates[-1]), date2num(dates2[-1])),
+                   color='blue', linewidth=2)
+        ax3.set_title('Datetime vs. Datetime')
+        ax3.xaxis.set_major_formatter(date_format)
+        ax3.yaxis.set_major_formatter(date_format)
 
     @mpl.style.context("default")
     def test_axvline(self):