Add a test for ErrorBarItem

pyqtgraph/graphicsItems/tests/test_ErrorBarItem.py

@@ -0,0 +1,39 @@
+import pytest
+from pyqtgraph.Qt import QtGui, QtCore
+import pyqtgraph as pg
+import numpy as np
+
+app = pg.mkQApp()
+
+
+def test_errorbaritem_defer_data():
+    plot = pg.PlotWidget()
+    plot.show()
+
+    # plot some data away from the origin to set the view rect
+    x = np.arange(5) + 10
+    curve = pg.PlotCurveItem(x=x, y=x)
+    plot.addItem(curve)
+    app.processEvents()
+    r_no_ebi = plot.viewRect()
+
+    # ErrorBarItem with no data shouldn't affect the view rect
+    err = pg.ErrorBarItem()
+    plot.addItem(err)
+    app.processEvents()
+    r_empty_ebi = plot.viewRect()
+
+    assert r_no_ebi == r_empty_ebi
+
+    err.setData(x=x, y=x, bottom=x, top=x)
+    app.processEvents()
+    r_ebi = plot.viewRect()
+
+    assert r_empty_ebi != r_ebi
+
+    # unset data, ErrorBarItem disappears and view rect goes back to original
+    err.setData(x=None, y=None)
+    app.processEvents()
+    r_clear_ebi = plot.viewRect()
+
+    assert r_clear_ebi == r_no_ebi