def METHOD_NAME(self, widget):
    '''Check the callback method for responding to changes in textboxes'''
    mocker.patch.object(widget.canvas, 'draw')
    mocker.patch.object(mpl.colors, 'Normalize')
    mocker.patch.object(mpl.colorbar, 'ColorbarBase')
    widget.vmin = 0.0
    widget.vmax = 100.0
    # good values in fields
    widget.txtMinAmplitude.setText("1.0")
    widget.txtMaxAmplitude.setText("10.0")
    widget.onAmplitudeChange()
    # Check the arguments to Normalize
    mpl.colors.Normalize.assert_called_with(vmin=1.0, vmax=10.0)
    assert widget.canvas.draw.called
    # Bad values in fields
    widget.txtMinAmplitude.setText("cake")
    widget.txtMaxAmplitude.setText("more cake")
    widget.onAmplitudeChange()
    # Check the arguments to Normalize - should be defaults
    mpl.colors.Normalize.assert_called_with(vmin=0.0, vmax=100.0)
    assert widget.canvas.draw.called