diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 6c9cbae08..422c4de62 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -55,7 +55,6 @@ jobs:
           channels: pyviz/label/dev,bokeh,conda-forge,nodefaults
           envs: -o tests -o sql
           cache: true
-          conda-mamba: mamba
         id: install
       - name: doit test_unit
         run: |
diff --git a/lumen/tests/sources/test_duckdb.py b/lumen/tests/sources/test_duckdb.py
index 744bcb3e2..3492fa1b2 100644
--- a/lumen/tests/sources/test_duckdb.py
+++ b/lumen/tests/sources/test_duckdb.py
@@ -15,6 +15,26 @@
 pytestmark = pytest.mark.skipif(DuckDBSource is None, reason="Duckdb is not installed")
 
 
+def assert_frame_equal_ignore_null_like(a, b):
+    """
+    From Pandas 2.1 we are getting this FutureWarning:
+        Mismatched null-like values nan and None found. In a future version,
+        pandas equality-testing functions (e.g. assert_frame_equal)
+        will consider these not-matching and raise.
+
+    Here we are converting all null-like values to np.nan.
+
+    Could be that in future release we get a keyword argument to ignore
+    this strict behavior
+
+    Reference: https://github.com/pandas-dev/pandas/pull/52081
+
+    """
+    a = a.fillna(np.nan)
+    b = b.fillna(np.nan)
+    pd.testing.assert_frame_equal(a, b)
+
+
 @pytest.fixture
 def duckdb_source():
     root = os.path.dirname(__file__)
@@ -43,7 +63,10 @@ def test_duckdb_get_tables(duckdb_source, source_tables):
     tables = duckdb_source.get_tables()
     assert not len(set(tables) - set(source_tables.keys()))
     for table in tables:
-        pd.testing.assert_frame_equal(duckdb_source.get(table), source_tables[table])
+        assert_frame_equal_ignore_null_like(
+            duckdb_source.get(table),
+            source_tables[table],
+        )
 
 
 def test_duckdb_get_schema(duckdb_source):
@@ -103,7 +126,7 @@ def test_duckdb_filter(duckdb_source, table_column_value_type, dask, expected_fi
     table, column, value, _ = table_column_value_type
     kwargs = {column: value}
     filtered = duckdb_source.get(table, __dask=dask, **kwargs)
-    pd.testing.assert_frame_equal(filtered, expected_filtered_df.reset_index(drop=True))
+    assert_frame_equal_ignore_null_like(filtered, expected_filtered_df.reset_index(drop=True))
 
 
 def test_duckdb_transforms(duckdb_source, source_tables):
diff --git a/lumen/tests/ui/test_imports.py b/lumen/tests/ui/test_imports.py
new file mode 100644
index 000000000..9710d0c7d
--- /dev/null
+++ b/lumen/tests/ui/test_imports.py
@@ -0,0 +1,12 @@
+from pathlib import Path
+
+import pytest
+
+ui_path = Path(__file__).parents[2] / "ui"
+ui_files = sorted(ui_path.glob("[!_]*.py"))
+
+
+@pytest.mark.parametrize("file", sorted(ui_files), ids=lambda f: f.name)
+def test_ui_import(file) -> None:
+    module_name = file.with_suffix("").name
+    __import__(f"lumen.ui.{module_name}")
diff --git a/lumen/tests/validation/test_layout.py b/lumen/tests/validation/test_layout.py
index 9dbc342f6..dc3f20a00 100644
--- a/lumen/tests/validation/test_layout.py
+++ b/lumen/tests/validation/test_layout.py
@@ -48,7 +48,7 @@ def test_layout_Facet(spec, msg):
         ),
         (
             {"format": "csvs"},
-            "Download component 'format' value failed validation: csvs",
+            "Download component 'format' value failed validation: .*?csvs",
         ),
     ),
     ids=["correct1", "correct2", "wrong_format"],
diff --git a/lumen/tests/validation/test_views.py b/lumen/tests/validation/test_views.py
index fc8c899fd..31ef41836 100644
--- a/lumen/tests/validation/test_views.py
+++ b/lumen/tests/validation/test_views.py
@@ -21,7 +21,7 @@
         ),
         (
             {"format": "csvs"},
-            "Download component 'format' value failed validation: csvs",
+            "Download component 'format' value failed validation: .*?csvs",
         ),
     ),
     ids=["correct1", "correct2", "missing_required", "wrong_format"],
@@ -51,7 +51,7 @@ def test_target_Download(spec, output):
         ),
         (
             {"type": "download", "format": "csvs"},
-            "DownloadView component 'format' value failed validation: csvs",
+            "DownloadView component 'format' value failed validation: .*?csvs",
         ),
         (
             {"format": "csv"},
diff --git a/lumen/ui/layouts.py b/lumen/ui/layouts.py
index 2086361b9..a923a4a34 100644
--- a/lumen/ui/layouts.py
+++ b/lumen/ui/layouts.py
@@ -218,7 +218,7 @@ class LayoutsEditor(WizardItem):
 
     title = param.String(default="")
 
-    spec = param.List(precedence=-1)
+    spec = param.List(allow_None=True, precedence=-1)
 
     sources = param.List(doc="Select a source")
 
diff --git a/lumen/ui/views.py b/lumen/ui/views.py
index 2e35340a9..f04bee241 100644
--- a/lumen/ui/views.py
+++ b/lumen/ui/views.py
@@ -30,7 +30,7 @@ class ViewsEditor(WizardItem):
 
     pipelines = param.List(label='Select a pipeline')
 
-    views = param.List()
+    views = param.List(allow_None=True)
 
     _template = """
     <span style="font-size: 2em">View Editor</span>
@@ -202,7 +202,7 @@ class ViewGallery(WizardItem, Gallery):
 
     path = param.Foldername()
 
-    spec = param.List()
+    spec = param.List(allow_None=True)
 
     views = param.List(default=[], precedence=-1, doc="""
         The list of views added to the dashboard.""")
diff --git a/setup.py b/setup.py
index 1243d9f57..d6c1c5c31 100644
--- a/setup.py
+++ b/setup.py
@@ -43,6 +43,7 @@ def get_setup_version(reponame):
         'pytest-cov',
         'codecov',
         'pre-commit',
+        'matplotlib >=3.4',  # Ubuntu + Python 3.9 installs old version matplotlib (3.3.2)
     ],
     'doc': [
         'nbsite >=0.8.2',