QGIS/python/plugins/processing/tests/README.md

Algorithm tests

To test QGIS Processing algorithms, YAML-based test cases are defined in the following files:

• qgis_algorithm_tests1.yaml through qgis_algorithm_tests5.yaml – QGIS core algorithm tests
• gdal_algorithm_vector_tests.yaml – GDAL vector-related tests
• gdal_algorithm_raster_tests.yaml – GDAL raster-related tests
• script_algorithm_tests.yaml – Custom script-based tests

All of these files are located in: python/plugins/processing/tests/testdata/

This file is structured with yaml syntax.

A basic test appears under the toplevel key tests and looks like this:

- name: centroid
  algorithm: qgis:polygoncentroids
  params:
    - type: vector
      name: polys.gml
  results:
    OUTPUT_LAYER:
      type: vector
      name: expected/polys_centroid.gml

How To

To add a new test for a QGIS Processing algorithm, follow these steps:

1. Run the Algorithm in QGIS

• Use the Processing Toolbox to run the algorithm you want to test.
• For vector outputs, prefer using GML format with XSD — this format supports mixed geometry types and offers good readability.
• Save the output to: python/plugins/processing/tests/testdata/expected/
• For input layers, reuse data already present in: python/plugins/processing/tests/testdata/

If additional data is required, place it under: python/plugins/processing/tests/testdata/custom/

2. Generate the Test Definition

• Open Processing ► History after running the algorithm.
• Locate your algorithm run, right-click it, and select Create Test.
• A new window will appear with the YAML test definition.

3. Add the Test to the Appropriate File

Paste the test definition into the correct YAML file inside: python/plugins/processing/tests/testdata/

Use the following guidelines:

• qgis_algorithm_tests1.yaml to qgis_algorithm_tests5.yaml: QGIS core algorithms
• gdal_algorithm_vector_tests.yaml: GDAL vector-related algorithms
• gdal_algorithm_raster_tests.yaml: GDAL raster-related algorithms
• script_algorithm_tests.yaml: Custom script-based tests

4. Example YAML Test Entry

- name: densify
  algorithm: qgis:densifygeometriesgivenaninterval
  params:
    - type: vector
      name: polys.gml
    - 2 # Interval
  results:
    OUTPUT:
      type: vector
      name: expected/polys_densify.gml

5. Adding Script-Based Tests

To create tests for custom Processing scripts:

• Place the script file in the following directory: python/plugins/processing/tests/testdata/scripts/
• The script file name must exactly match the script algorithm name used in your test definition.

For example, if your test refers to an algorithm named my_custom_buffer, your script should be saved as: python/plugins/processing/tests/testdata/scripts/my_custom_buffer.py

Params and results

Trivial type parameters

Params and results are specified as lists or dictionaries:

params:
  INTERVAL: 5
  INTERPOLATE: True
  NAME: A processing test

or

params:
  - 2
  - string
  - another param

Layer type parameters

You will often need to specify layers as parameters. To specify a layer you will need to specify:

• the type
  • vector or raster
• a name
  • relative path like expected/polys_centroid.gml

This is what it looks like in action:

params:
  PAR: 2
  STR: string
  LAYER:
    type: vector
    name: polys.gml
  OTHER: another param

File type parameters

If you need an external file for the algorithm test, you need to specify the 'file' type and the (relative) path to the file in its 'name':

params:
  PAR: 2
  STR: string
  EXTFILE:
    type: file
    name: custom/grass7/extfile.txt
  OTHER: another param

Results

Results are specified very similar.

Basic vector files

It couldn't be more trivial

    OUTPUT:
      name: expected/qgis_intersection.gml
      type: vector

Add the expected GML and XSD in the folder.

Vector with tolerance

Sometimes, different platforms create slightly different results that are still acceptable. In such cases — and only in such cases — you can use additional properties to define how a layer is compared.

To handle a certain tolerance for output values, you can specify a compare property for an output. The compare property can include sub-properties for fields and geometry.

The fields section lets you control how precisely specific fields are compared. You can:

• Use precision to set a numerical tolerance.
• Use skip to ignore a field entirely.
• Use __all__ to apply the same tolerance to all fields.

The geometry section also accepts a precision value, which applies to each vertex coordinate.

Example configuration:

OUTPUT:
  type: vector
  name: expected/abcd.gml
  compare:
    fields:
      __all__:
        precision: 5 # compare to a precision of .00001 on all fields
      A: skip # skip field A
    geometry:
      precision: 5 # compare coordinates with a precision of 5 digits

Raster files

Raster files are compared with a hash checksum. This is calculated when you create a test from the processing history.

OUTPUT:
  type: rasterhash
  hash: f1fedeb6782f9389cf43590d4c85ada9155ab61fef6dc285aaeb54d6

Files

You can compare the content of an output file by an expected result reference file

OUTPUT_HTML_FILE:
  name: expected/basic_statistics_string.html
  type: file

Or you can use one or more regular expressions that will be matched against the file content

OUTPUT:
  name: layer_info.html
  type: regex
  rules:
    - 'Extent: \(-1.000000, -3.000000\) - \(11.000000, 5.000000\)'
    - 'Geometry: Line String'
    - 'Feature Count: 6'

Directories

You can compare the content of an output directory with an expected result reference directory

OUTPUT_DIR:
  name: expected/tiles_xyz/test_1
  type: directory

Algorithm Context

There are few more definitions that can modify context of the algorithm - these can be specified at top level of test:

• project - will load a specified QGIS project file before running the algorithm. If not specified, algorithm will run with empty project
• project_crs - overrides the default project CRS - e.g. EPSG:27700
• ellipsoid - overrides the default project ellipsoid used for measurements - e.g. GRS80

Running tests locally

ctest -V -R ProcessingQgisAlgorithmsTest

or one of the following value listed in the CMakelists.txt