diff --git a/lcviz/helper.py b/lcviz/helper.py
index 16743984..a82d8817 100644
--- a/lcviz/helper.py
+++ b/lcviz/helper.py
@@ -31,7 +31,7 @@ def _get_range_subset_bounds(self, subset_state, *args, **kwargs):
         # TODO: use display units once implemented in Glue for ScatterViewer
         # units = u.Unit(viewer.state.x_display_unit)
         units = u.Unit(viewer.time_unit)
-    else:
+    else:  # pragma: no cover
         raise ValueError("Unable to find time axis units")
 
     region = reference_time + u.Quantity([subset_state.lo * units, subset_state.hi * units])
diff --git a/lcviz/parsers.py b/lcviz/parsers.py
index e9401ab2..e9268c83 100644
--- a/lcviz/parsers.py
+++ b/lcviz/parsers.py
@@ -1,9 +1,7 @@
 import os
-from astropy.io import fits
 from glue.config import data_translator
 from jdaviz.core.registries import data_parser_registry
-from lightkurve import LightCurve, KeplerLightCurve, TessLightCurve
-from lightkurve.io.detect import detect_filetype
+import lightkurve
 
 __all__ = ["light_curve_parser"]
 
@@ -17,21 +15,11 @@ def light_curve_parser(app, file_obj, data_label=None, show_in_viewer=True, **kw
         if data_label is None:
             data_label = os.path.splitext(os.path.basename(file_obj))[0]
 
-        # detect the type light curve in a FITS file:
-        with fits.open(file_obj) as hdulist:
-            filetype = detect_filetype(hdulist)
-
-        # get the constructor for this type of light curve:
-        filetype_to_cls = {
-            'KeplerLightCurve': KeplerLightCurve,
-            'TessLightCurve': TessLightCurve
-        }
-        cls = filetype_to_cls[filetype]
         # read the light curve:
-        light_curve = cls.read(file_obj)
+        light_curve = lightkurve.read(file_obj)
 
     # load a LightCurve object:
-    elif isinstance(file_obj, LightCurve):
+    elif isinstance(file_obj, lightkurve.LightCurve):
         light_curve = file_obj
 
     # make a data label:
diff --git a/lcviz/plugins/ephemeris/ephemeris.py b/lcviz/plugins/ephemeris/ephemeris.py
index 4eb0a87e..38aecee0 100644
--- a/lcviz/plugins/ephemeris/ephemeris.py
+++ b/lcviz/plugins/ephemeris/ephemeris.py
@@ -280,7 +280,7 @@ def _on_component_remove(self, lbl):
         _ = self._ephemerides.pop(lbl, {})
         # remove the corresponding viewer, if it exists
         viewer_item = self.app._viewer_item_by_id(self._phase_viewer_id(lbl))
-        if viewer_item is None:
+        if viewer_item is None:  # pragma: no cover
             return
         cid = viewer_item.get('id', None)
         if cid is not None:
@@ -346,7 +346,7 @@ def update_ephemeris(self, component=None, t0=None, period=None, dpdt=None):
         if component is None:
             component = self.component_selected
 
-        if component not in self.component.choices:
+        if component not in self.component.choices:  # pragma: no cover
             raise ValueError(f"component must be one of {self.component.choices}")
 
         existing_ephem = self._ephemerides.get(component, {})
@@ -411,7 +411,7 @@ def _update_periodogram(self, *args):
                 self.method_spinner = False
                 self.method_err = str(err)
                 return
-        else:
+        else:  # pragma: no cover
             self.method_spinner = False
             raise NotImplementedError(f"periodogram not implemented for {self.method}")
 
diff --git a/lcviz/plugins/flatten/flatten.py b/lcviz/plugins/flatten/flatten.py
index 7d550f7a..d907e542 100644
--- a/lcviz/plugins/flatten/flatten.py
+++ b/lcviz/plugins/flatten/flatten.py
@@ -97,7 +97,7 @@ def marks(self):
     @observe('default_to_overwrite', 'dataset_selected')
     def _set_default_results_label(self, event={}):
         '''Generate a label and set the results field to that value'''
-        if not hasattr(self, 'dataset'):
+        if not hasattr(self, 'dataset'):  # pragma: no cover
             return
 
         self.add_results.label_whitelist_overwrite = [self.dataset_selected]
@@ -125,7 +125,7 @@ def flatten(self, add_data=True):
             The trend used to flatten the light curve.
         """
         input_lc = self.dataset.selected_obj
-        if input_lc is None:
+        if input_lc is None:  # pragma: no cover
             raise ValueError("no input dataset selected")
 
         output_lc, trend_lc = input_lc.flatten(return_trend=True,
diff --git a/lcviz/state.py b/lcviz/state.py
index eebd7ab5..ddf393e2 100644
--- a/lcviz/state.py
+++ b/lcviz/state.py
@@ -11,7 +11,7 @@ def _reset_att_limits(self, ax):
         # override glue's _reset_x/y_limits to account for all layers,
         # not just reference data
         att = f'{ax}_att'
-        if getattr(self, att) is None:
+        if getattr(self, att) is None:  # pragma: no cover
             return
 
         ax_min, ax_max = np.inf, -np.inf
@@ -21,14 +21,14 @@ def _reset_att_limits(self, ax):
                 ax_min = min(ax_min, np.nanmin(ax_data))
                 ax_max = max(ax_max, np.nanmax(ax_data))
 
-        if not np.all(np.isfinite([ax_min, ax_max])):
+        if not np.all(np.isfinite([ax_min, ax_max])):  # pragma: no cover
             return
 
         with delay_callback(self, f'{ax}_min', f'{ax}_max'):
             setattr(self, f'{ax}_min', ax_min)
             setattr(self, f'{ax}_max', ax_max)
 
-    def _reset_x_limit(self, *event):
+    def _reset_x_limits(self, *event):
         self._reset_att_limits('x')
 
     def _reset_y_limits(self, *event):
@@ -39,7 +39,7 @@ def reset_limits(self, *event):
         y_min, y_max = np.inf, -np.inf
 
         for layer in self.layers:
-            if not layer.visible:
+            if not layer.visible:  # pragma: no cover
                 continue
 
             x_data = layer.layer.data.get_data(self.x_att)
diff --git a/lcviz/tests/test_parser.py b/lcviz/tests/test_parser.py
index 5a210c73..c4585e4f 100644
--- a/lcviz/tests/test_parser.py
+++ b/lcviz/tests/test_parser.py
@@ -1,52 +1,53 @@
-# import pytest
+import pytest
 import numpy as np
 from glue.core.roi import XRangeROI, YRangeROI
 from astropy.time import Time
-# from astropy.utils.data import download_file
+from astropy.utils.data import download_file
 from lightkurve import LightCurve
-# from lightkurve.io import kepler
+from lightkurve.io import kepler
 import astropy.units as u
 
 from lcviz.utils import TimeCoordinates
 
-# @pytest.mark.remote_data
-# def test_kepler_via_mast_local_file(helper):
-#     url = (
-#         'https://archive.stsci.edu/pub/kepler/'
-#         'lightcurves/0014/001429092/kplr001429092-2009166043257_llc.fits'
-#     )  # 188 KB
-#
-#     path = download_file(url, cache=True, timeout=100)
-#     helper.load_data(path)
-#
-#     data = helper.app.data_collection[0]
-#     flux_arr = data['flux']
-#     flux_unit = u.Unit(data.get_component('flux').units)
-#     flux = flux_arr * flux_unit
-#
-#     assert isinstance(data.coords, TimeCoordinates)
-#     assert isinstance(flux, u.Quantity)
-#     assert flux.unit.is_equivalent(u.electron / u.s)
-#
-#
-# @pytest.mark.remote_data
-# def test_kepler_via_mast_preparsed(helper):
-#     url = (
-#         'https://archive.stsci.edu/pub/kepler/'
-#         'lightcurves/0014/001429092/kplr001429092-2009166043257_llc.fits'
-#     )  # 188 KB
-#
-#     light_curve = kepler.read_kepler_lightcurve(url)
-#     helper.load_data(light_curve)
-#
-#     data = helper.app.data_collection[0]
-#     flux_arr = data['flux']
-#     flux_unit = u.Unit(data.get_component('flux').units)
-#     flux = flux_arr * flux_unit
-#
-#     assert isinstance(data.coords, TimeCoordinates)
-#     assert isinstance(flux, u.Quantity)
-#     assert flux.unit.is_equivalent(u.electron / u.s)
+
+@pytest.mark.remote_data
+def test_kepler_via_mast_local_file(helper):
+    url = (
+        'https://archive.stsci.edu/pub/kepler/'
+        'lightcurves/0014/001429092/kplr001429092-2009166043257_llc.fits'
+    )  # 188 KB
+
+    path = download_file(url, cache=True, timeout=100)
+    helper.load_data(path)
+
+    data = helper.app.data_collection[0]
+    flux_arr = data['flux']
+    flux_unit = u.Unit(data.get_component('flux').units)
+    flux = flux_arr * flux_unit
+
+    assert isinstance(data.coords, TimeCoordinates)
+    assert isinstance(flux, u.Quantity)
+    assert flux.unit.is_equivalent(u.electron / u.s)
+
+
+@pytest.mark.remote_data
+def test_kepler_via_mast_preparsed(helper):
+    url = (
+     'https://archive.stsci.edu/pub/kepler/'
+     'lightcurves/0014/001429092/kplr001429092-2009166043257_llc.fits'
+    )  # 188 KB
+
+    light_curve = kepler.read_kepler_lightcurve(url)
+    helper.load_data(light_curve)
+
+    data = helper.app.data_collection[0]
+    flux_arr = data['flux']
+    flux_unit = u.Unit(data.get_component('flux').units)
+    flux = flux_arr * flux_unit
+
+    assert isinstance(data.coords, TimeCoordinates)
+    assert isinstance(flux, u.Quantity)
+    assert flux.unit.is_equivalent(u.electron / u.s)
 
 
 def test_synthetic_lc(helper):
diff --git a/lcviz/tests/test_plugin_ephemeris.py b/lcviz/tests/test_plugin_ephemeris.py
index 587e170e..a837b6d3 100644
--- a/lcviz/tests/test_plugin_ephemeris.py
+++ b/lcviz/tests/test_plugin_ephemeris.py
@@ -31,6 +31,22 @@ def test_plugin_ephemeris(helper, light_curve_like_kepler_quarter):
     assert 'renamed custom component' in ephem.ephemerides
     assert len(helper.app.get_viewer_ids()) == 3
 
+    assert ephem.component == 'renamed custom component'
+    assert ephem.period == 3.14
+    assert ephem.ephemeris['period'] == 3.14
+    # modify the ephemeris of the NON-selected ephemeris component
+    ephem.update_ephemeris(component='default', period=2)
+    assert ephem.period == 3.14
+    assert ephem.ephemerides['default']['period'] == 2
+
     ephem.remove_component('renamed custom component')
     assert len(ephem.ephemerides) == 1
     assert len(helper.app.get_viewer_ids()) == 2
+    assert ephem.component == 'default'
+    assert ephem.period == 2
+
+    assert ephem.method.selected == 'Lomb-Scargle'
+    ephem.method = 'Box Least Squares'
+    assert ephem._obj.method_err == ''
+    ephem._obj.vue_adopt_period_at_max_power()
+    assert ephem.period != 2
diff --git a/lcviz/tests/test_plugin_flatten.py b/lcviz/tests/test_plugin_flatten.py
index 12110fe7..d14a0089 100644
--- a/lcviz/tests/test_plugin_flatten.py
+++ b/lcviz/tests/test_plugin_flatten.py
@@ -4,27 +4,56 @@
 from lcviz.marks import LivePreviewTrend, LivePreviewFlattened
 
 
-def _get_marks_from_viewer(viewer, cls=(LivePreviewTrend, LivePreviewFlattened)):
-    return [m for m in viewer.figure.marks if isinstance(m, cls)]
+def _get_marks_from_viewer(viewer, cls=(LivePreviewTrend, LivePreviewFlattened),
+                           include_not_visible=False):
+    return [m for m in viewer.figure.marks if isinstance(m, cls)
+            if include_not_visible or m.visible]
 
 
 def test_plugin_flatten(helper, light_curve_like_kepler_quarter):
     helper.load_data(light_curve_like_kepler_quarter)
     tv = helper.app.get_viewer(helper._default_time_viewer_reference_name)
 
-    f = helper.plugins['Flatten']
-    f.plugin_opened = True
     ephem = helper.plugins['Ephemeris']
     pv = ephem.create_phase_viewer()
+    f = helper.plugins['Flatten']
 
-    assert len(_get_marks_from_viewer(tv)) == 2
-    assert len(_get_marks_from_viewer(pv)) == 1
-
-    orig_label = f.dataset.selected
-    assert f.dataset.selected_obj is not None
-    assert f._obj.add_results.label_overwrite is True
-    assert f._obj.add_results.label == orig_label
-    f.flatten(add_data=True)
+    # no marks until plugin opened/active
+    assert len(_get_marks_from_viewer(tv)) == 0
+    assert len(_get_marks_from_viewer(pv)) == 0
+
+    with f.as_active():
+        assert len(_get_marks_from_viewer(tv)) == 2
+        assert len(_get_marks_from_viewer(pv)) == 1
+
+        # update period which should update phasing in phase-viewer
+        ephem.period = 1.2
+
+        before_polyorder = f.polyorder
+        before_update = _get_marks_from_viewer(tv)[0].y
+
+        # test error handling in live-preview
+        f.polyorder = -1
+        assert f._obj.flatten_err != ''
+        assert len(_get_marks_from_viewer(tv)) == 0
+        assert len(_get_marks_from_viewer(pv)) == 0
+
+        # update polyorder (live-preview should re-appear and have changed from before)
+        f.polyorder = before_polyorder + 1
+        assert f._obj.flatten_err == ''
+        after_update = _get_marks_from_viewer(tv)[0].y
+        assert not np.allclose(before_update, after_update)
+
+        orig_label = f.dataset.selected
+        assert f.dataset.selected_obj is not None
+        assert f._obj.add_results.label_overwrite is True
+        assert f._obj.add_results.label == orig_label
+        f._obj.vue_apply(add_data=True)
+        assert f._obj.flatten_err == ''
+
+    # marks are hidden
+    assert len(_get_marks_from_viewer(tv)) == 0
+    assert len(_get_marks_from_viewer(pv)) == 0
 
 
 def test_no_overwrite(helper, light_curve_like_kepler_quarter):
diff --git a/lcviz/tests/test_viewers.py b/lcviz/tests/test_viewers.py
new file mode 100644
index 00000000..66f15da6
--- /dev/null
+++ b/lcviz/tests/test_viewers.py
@@ -0,0 +1,19 @@
+
+def test_reset_limits(helper, light_curve_like_kepler_quarter):
+    helper.load_data(light_curve_like_kepler_quarter)
+    tv = helper.app.get_viewer(helper._default_time_viewer_reference_name)
+
+    orig_xlims = (tv.state.x_min, tv.state.x_max)
+    orig_ylims = (tv.state.y_min, tv.state.y_max)
+    # set xmin and ymin to midpoints
+    new_xmin = (tv.state.x_min + tv.state.x_max) / 2
+    new_ymin = (tv.state.y_min + tv.state.y_max) / 2
+    tv.state.x_min = new_xmin
+    tv.state.y_min = new_ymin
+
+    tv.state._reset_x_limits()
+    assert tv.state.x_min == orig_xlims[0]
+    assert tv.state.y_min == new_ymin
+
+    tv.state._reset_y_limits()
+    assert tv.state.y_min == orig_ylims[0]
diff --git a/lcviz/utils.py b/lcviz/utils.py
index 1bb0e28e..3dbff498 100644
--- a/lcviz/utils.py
+++ b/lcviz/utils.py
@@ -25,7 +25,7 @@ class TimeCoordinates(Coordinates):
     """
 
     def __init__(self, times, reference_time=None, unit=u.d):
-        if not isinstance(times, Time):
+        if not isinstance(times, Time):  # pragma: no cover
             raise TypeError('values should be a Time instance')
         self._index = np.arange(len(times))
         self._times = times
@@ -44,7 +44,7 @@ def time_axis(self):
         return self._times
 
     def world_to_pixel_values(self, *world):
-        if len(world) > 1:
+        if len(world) > 1:  # pragma: no cover
             raise ValueError('TimeCoordinates is a 1-d coordinate class '
                              'and only accepts a single scalar or array to convert')
         return interp1d(
@@ -52,7 +52,7 @@ def world_to_pixel_values(self, *world):
         )(world[0])
 
     def pixel_to_world_values(self, *pixel):
-        if len(pixel) > 1:
+        if len(pixel) > 1:  # pragma: no cover
             raise ValueError('SpectralCoordinates is a 1-d coordinate class '
                              'and only accepts a single scalar or array to convert')
         return interp1d(