diff --git a/packages/data/src/pyearthtools/data/transforms/normalisation/default.py b/packages/data/src/pyearthtools/data/transforms/normalisation/default.py
index 34019014..b4df1784 100644
--- a/packages/data/src/pyearthtools/data/transforms/normalisation/default.py
+++ b/packages/data/src/pyearthtools/data/transforms/normalisation/default.py
@@ -44,7 +44,7 @@ def open_file(file: str | tuple | dict):
     data = open_files(file)
     if isinstance(data, (xr.Dataset, xr.DataArray)):
         data = get_default_transforms()(data)
-        data = pyearthtools.data.transforms.coordinates.drop("time", ignore_missing=True)(data)
+        data = pyearthtools.data.transforms.coordinates.Drop("time", ignore_missing=True)(data)
     return data
 
 
@@ -61,7 +61,7 @@ def under_func(*args, **kwargs):
     return under_func
 
 
-class normaliser:
+class Normaliser:
     def __init__(
         self,
         index: pyearthtools.data.AdvancedTimeIndex,
@@ -214,7 +214,7 @@ def get_aggregation(
         # )
 
         aggregated_data = get_and_print(
-            lambda: pyearthtools.data.transforms.aggregation.over(method, dims)(
+            lambda: pyearthtools.data.transforms.aggregation.over(method=method, dimension=dims)(
                 self.index.series(
                     **retrieval_args,
                     transforms=transforms,
diff --git a/packages/data/src/pyearthtools/data/transforms/normalisation/normalise.py b/packages/data/src/pyearthtools/data/transforms/normalisation/normalise.py
index d0969dd9..91a7f448 100644
--- a/packages/data/src/pyearthtools/data/transforms/normalisation/normalise.py
+++ b/packages/data/src/pyearthtools/data/transforms/normalisation/normalise.py
@@ -23,18 +23,18 @@
 
 xr.set_options(keep_attrs=True)
 
-from pyearthtools.data.transforms.normalisation.default import normaliser, open_file
+from pyearthtools.data.transforms.normalisation.default import Normaliser, open_file
 from pyearthtools.data.transforms.transform import FunctionTransform, Transform
 
 
-class Normalise(normaliser):
+class Normalise(Normaliser):
     """
     Normalise incoming data.
 
     Either call this class, or get attribute for specific normalisation strategy
     """
 
-    @functools.wraps(normaliser.__init__)
+    @functools.wraps(Normaliser.__init__)
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
 
diff --git a/packages/data/src/pyearthtools/data/transforms/normalisation/unnormalise.py b/packages/data/src/pyearthtools/data/transforms/normalisation/unnormalise.py
index af8b2047..38d4b262 100644
--- a/packages/data/src/pyearthtools/data/transforms/normalisation/unnormalise.py
+++ b/packages/data/src/pyearthtools/data/transforms/normalisation/unnormalise.py
@@ -21,16 +21,16 @@
 import numpy as np
 import xarray as xr
 
-from pyearthtools.data.transforms.normalisation.default import normaliser, open_file
+from pyearthtools.data.transforms.normalisation.default import Normaliser, open_file
 from pyearthtools.data.transforms.transform import FunctionTransform, Transform
 
 xr.set_options(keep_attrs=True)
 
 
-class Unnormalise(normaliser):
+class Unnormalise(Normaliser):
     """Unnormalise Incoming Data"""
 
-    @functools.wraps(normaliser)
+    @functools.wraps(Normaliser)
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
 
diff --git a/packages/data/src/pyearthtools/data/transforms/transform.py b/packages/data/src/pyearthtools/data/transforms/transform.py
index a2348749..7d29f879 100644
--- a/packages/data/src/pyearthtools/data/transforms/transform.py
+++ b/packages/data/src/pyearthtools/data/transforms/transform.py
@@ -240,8 +240,8 @@ def apply(self, dataset: XR_TYPES | tuple[XR_TYPES] | list[XR_TYPES] | dict[str,
     def __call__(self, dataset: XR_TYPES | tuple[XR_TYPES] | list[XR_TYPES] | dict[str, XR_TYPES]) -> XR_TYPES | Any:
 
         # Do not try to transform empty datasets
-        if not dataset:
-            return dataset
+        if dataset is None:
+            return None
 
         for transform in self._transforms:
             dataset = transform(dataset)
diff --git a/packages/data/tests/data/transform/normalisation/test_default.py b/packages/data/tests/data/transform/normalisation/test_default.py
new file mode 100644
index 00000000..b43a7651
--- /dev/null
+++ b/packages/data/tests/data/transform/normalisation/test_default.py
@@ -0,0 +1,86 @@
+import pyearthtools.data.transforms.normalisation
+from pyearthtools.data.transforms.normalisation import default
+from pyearthtools.data.time import Petdt
+import pyearthtools.data.indexes
+import xarray as xr
+import numpy as np
+import pytest
+
+sample_da = xr.DataArray(coords={"latitude": [1,2,3,4], 
+                                 "longitude": [1,2,3],
+                                 "time": ["2023-02"]
+                                 },
+                         data=np.ones((4,3,1)))
+
+sample_ds = xr.Dataset(coords={"latitude": [1,2,3,4], "longitude": [1,2,3], "time": ["2023-02"]},
+                       data_vars={"temperature": sample_da})
+
+
+def test_open_file(monkeypatch):
+
+    monkeypatch.setattr(pyearthtools.data.transforms.normalisation.default, 
+                             'open_files', 
+                             lambda x: sample_da)
+
+    result = default.open_file("pretend_filename.nc")
+    assert result is not None
+
+
+def test_Normaliser(monkeypatch):
+
+    monkeypatch.setattr("pyearthtools.data.indexes.AdvancedTimeIndex.__abstractmethods__", set())
+
+    data_interval = "day"
+    ati = pyearthtools.data.indexes.AdvancedTimeIndex(data_interval)
+    monkeypatch.setattr(ati, "get", lambda x: sample_da)
+    start = Petdt("2023-02")
+    end = Petdt("2023-03")
+
+    n = default.Normaliser(ati, start, end, "month")
+    n.check_init_args()
+
+    result = n.get_average("temperature")
+    assert result == 1
+
+    r_mean, r_std = n.get_deviation("temperature")
+    assert r_mean == 1
+    assert r_std == 0
+
+    r_anomaly = n.get_anomaly("temperature")
+    assert r_anomaly is not None
+
+    # FIXME: Need to update the whole test creation to be a time-aware dataset
+    # r_range = n.get_range("temperature")
+    # assert r_range["temperature"]["max"] == 1
+    # assert r_range["temperature"]["min"] == 1
+
+    result = n.none
+    assert result is not None
+
+def test_Normaliser_errors(monkeypatch):
+
+    monkeypatch.setattr("pyearthtools.data.indexes.AdvancedTimeIndex.__abstractmethods__", set())
+
+    data_interval = "day"
+    ati = pyearthtools.data.indexes.AdvancedTimeIndex(data_interval)
+    monkeypatch.setattr(ati, "get", lambda x: sample_da)
+    start = Petdt("2023-02")
+    end = Petdt("2023-03")
+
+    n = default.Normaliser(ati, start, end, "month")
+
+    with pytest.raises(NotImplementedError):
+        n.function()
+
+
+    not_implemented = [n.log, n.anomaly, n.deviation, n.deviation_spatial, n.range]
+    for ni in not_implemented:
+        with pytest.raises(NotImplementedError):
+            ni()
+
+
+
+
+
+
+