When developing an application (e.g., custom algorithms) that rely on a custom processing provider (e.g., WhiteBox tools), it can be useful to run/develop as a standalone app (i.e., not within QGIS). How can I call whitebox QGIS algorithims in my standalone tests?

import pytest #pytest-qgis also installed

def qproj(qgis_app, qgis_processing):
    from qgis import processing
    processing.run('wbt:ConvertNodataToZero', { 'input' : r'path/layer.tif', 'output' : 'TEMPORARY_OUTPUT'})

this fails with _core.QgsProcessingException: Error: Algorithm wbt:ConvertNodataToZero not found

1 Answer 1


first, ensure the QGIS user path where the wbt plugin is installed is added to your PYTHONPATH (e.g., c:\Users\cefect\AppData\Local\QGIS\QGIS3\profiles\dev\python\plugins).

then, create a fixture that adds the custom provider and sets your wbt executable location:

def wbt_init(qgis_app, qgis_processing):
    """initilze the WhiteBoxTools processing provider"""
    #load the provider
    from wbt_for_qgis.wbtprovider import WbtProvider #be sure to add the profile folder to sys.path
    whitebox_provider = WbtProvider()
    #add to the registry
    assert qgis_app.processingRegistry().addProvider(whitebox_provider)
    #add the exe setting
    from processing.core.ProcessingConfig import ProcessingConfig
    wbt_exe = r'l:\06_SOFT\whitebox\v2.2.0\whitebox_tools.exe'    
    ProcessingConfig.setSettingValue('WBT_EXECUTABLE', wbt_exe)
    return whitebox_provider #needs to be held somewhere

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