DateAxisItem: AxisItem unlinking tests and doc fixed (#1179)

* Added test_AxisItem by @mliberty1

As found in https://github.com/pyqtgraph/pyqtgraph/pull/917

* test_AxisItem: Fit to current implementation

* DateAxisItem: Fix documentation to zoomLevels

zoomLevels is not intended to be set by the user (see discussion in converstation from
https://github.com/pyqtgraph/pyqtgraph/pull/1154/files#diff-aefdb23660d0963df0dff3a116baded8
). Also, `zoomLevelWidths` does currently not exist.
This commit adapts the documentation to reflect that.

* DateAxisItem: Do not publish ZoomLevel

* DateAxisItem testing: Removed unnecessary monkeypatch fixture

Co-authored-by: 2xB <2xB@users.noreply.github.com>

pyqtgraph/graphicsItems/DateAxisItem.py

@@ -6,7 +6,7 @@ from datetime import datetime, timedelta
 from .AxisItem import AxisItem
 from ..pgcollections import OrderedDict
 
-__all__ = ['DateAxisItem', 'ZoomLevel']
+__all__ = ['DateAxisItem']
 
 MS_SPACING = 1/1000.0
 SECOND_SPACING = 1
@@ -260,9 +260,8 @@ class DateAxisItem(AxisItem):
         overriding this function or setting a different set of zoom levels
         than the default one. The `zoomLevels` variable is a dictionary with the
         maximal distance of ticks in seconds which are allowed for each zoom level
-        before the axis switches to the next coarser level. To create custom
+        before the axis switches to the next coarser level. To customize the zoom level
-        zoom levels, override this function and provide custom `zoomLevelWidths` and
+        selection, override this function.
-        `zoomLevels`.
         """
         padding = 10
         

pyqtgraph/graphicsItems/tests/test_AxisItem.py

@@ -30,3 +30,60 @@ def test_AxisItem_stopAxisAtTick(monkeypatch):
     plot.show()
     app.processEvents()
     plot.close()
+
+
+def test_AxisItem_viewUnlink():
+    plot = pg.PlotWidget()
+    view = plot.plotItem.getViewBox()
+    axis = plot.getAxis("bottom")
+    assert axis.linkedView() == view
+    axis.unlinkFromView()
+    assert axis.linkedView() is None
+
+
+class FakeSignal:
+
+    def __init__(self):
+        self.calls = []
+
+    def connect(self, *args, **kwargs):
+        self.calls.append('connect')
+
+    def disconnect(self, *args, **kwargs):
+        self.calls.append('disconnect')
+
+
+class FakeView:
+
+    def __init__(self):
+        self.sigYRangeChanged = FakeSignal()
+        self.sigXRangeChanged = FakeSignal()
+        self.sigResized = FakeSignal()
+
+
+def test_AxisItem_bottomRelink():
+    axis = pg.AxisItem('bottom')
+    fake_view = FakeView()
+    axis.linkToView(fake_view)
+    assert axis.linkedView() == fake_view
+    assert fake_view.sigYRangeChanged.calls == []
+    assert fake_view.sigXRangeChanged.calls == ['connect']
+    assert fake_view.sigResized.calls == ['connect']
+    axis.unlinkFromView()
+    assert fake_view.sigYRangeChanged.calls == []
+    assert fake_view.sigXRangeChanged.calls == ['connect', 'disconnect']
+    assert fake_view.sigResized.calls == ['connect', 'disconnect']
+
+
+def test_AxisItem_leftRelink():
+    axis = pg.AxisItem('left')
+    fake_view = FakeView()
+    axis.linkToView(fake_view)
+    assert axis.linkedView() == fake_view
+    assert fake_view.sigYRangeChanged.calls == ['connect']
+    assert fake_view.sigXRangeChanged.calls == []
+    assert fake_view.sigResized.calls == ['connect']
+    axis.unlinkFromView()
+    assert fake_view.sigYRangeChanged.calls == ['connect', 'disconnect']
+    assert fake_view.sigXRangeChanged.calls == []
+    assert fake_view.sigResized.calls == ['connect', 'disconnect']