Add tests

panel/_templates/kernel_error.html

@@ -95,10 +95,8 @@
     <fast-design-system-provider id="header-design-provider" use-defaults background-color="#000000">
       <section class="header">
         <div class="header-grid">
-          <h1>
-            <fast-anchor id="title" href="https://panel.holoviz.org" appearance="neutral" target="_self"><img id="panel-logo" src="https://panel.holoviz.org/_static/logo_horizontal.png"/></fast-anchor>
-            <fast-tooltip anchor="title">Click to visit the Panel web site</fast-tooltip>
-          </h1>
+          <fast-anchor id="title" href="https://panel.holoviz.org" appearance="neutral" target="_self"><img id="panel-logo" src="https://panel.holoviz.org/_static/logo_horizontal.png"/></fast-anchor>
+          <fast-tooltip anchor="title">Click to visit the Panel web site</fast-tooltip>
           <h1>Kernel Error: {{ error }}</h1>
         </div>
       </section>

panel/tests/conftest.py

@@ -5,8 +5,10 @@
 import re
 import shutil
 import tempfile
+import time
 
 from contextlib import contextmanager
+from subprocess import PIPE, Popen
 
 import pytest
 
@@ -250,3 +252,29 @@ def threads():
         yield 4
     finally:
         config.nthreads = None
+
+@pytest.fixture
+def change_test_dir(request):
+    os.chdir(request.fspath.dirname)
+    yield
+    os.chdir(request.config.invocation_dir)
+
+@pytest.fixture
+def jupyter_server(port, change_test_dir):
+    process = Popen(['jupyter', 'server', '--port', str(port)], stdout=PIPE, stderr=PIPE, bufsize=1, encoding='utf-8')
+    os.set_blocking(process.stderr.fileno(), False)
+    while True:
+        for _ in range(2):
+            line = process.stderr.readline()
+        time.sleep(0.02)
+        if "http://127.0.0.1:" in line:
+            url = "http://127.0.0.1:"
+            break
+        if "http://localhost:" in line:
+            url = "http://localhost:"
+            break
+    port = int(line.split(url)[-1][:4])
+    PORT[0] = port
+    process.args[-1] = str(port)
+    yield process
+    process.kill()

panel/tests/ui/io/app.py

@@ -0,0 +1,12 @@
+import panel as pn
+
+button = pn.widgets.Button(name='Click')
+
+string = pn.pane.Str(object=0, css_classes=['string'])
+
+def cb(event):
+    string.object += 1
+
+button.on_click(cb)
+
+pn.Row(button, string).servable()

panel/tests/ui/io/test_jupyter_server_extension.py

@@ -0,0 +1,42 @@
+import sys
+import time
+
+import pytest
+
+pytestmark = pytest.mark.ui
+
+not_windows = pytest.mark.skipif(sys.platform=='win32', reason="Does not work on Windows")
+
+@not_windows
+def test_jupyter_server(page, jupyter_server):
+    port = jupyter_server.args[-1]
+
+    page.goto(f"http://localhost:{port}/panel-preview/render/app.py")
+
+    assert page.text_content('.bk.string') == '0'
+
+    page.click('.bk.bk-btn')
+    time.sleep(0.1)
+
+    assert page.text_content('.bk.string') == '1'
+
+    page.click('.bk.bk-btn')
+    time.sleep(0.1)
+
+    assert page.text_content('.bk.string') == '2'
+
+@not_windows
+def test_jupyter_server_kernel_error(page, jupyter_server):
+    port = jupyter_server.args[-1]
+
+    page.goto(f"http://localhost:{port}/panel-preview/render/app.py?kernel=blah")
+
+    assert page.text_content('h1') == 'Kernel Error: No such kernel blah'
+
+    page.select_option('select#kernel-select', 'python3')
+
+    assert page.text_content('.bk.string') == '0'
+    page.click('.bk.bk-btn')
+    time.sleep(0.1)
+
+    assert page.text_content('.bk.string') == '1'