Allow specifying a 'primary key' field when comparing layers for

processing tests

Some algorithms will return results in different orders, e.g.
due to the use of dicts or other methods which do not guarantee
a fixed return order.

Using a primary key to do the feature match allows us to flexibly
handle these situations and provide tests for these algorithms.

python/plugins/processing/tests/AlgorithmsTestBase.py

@@ -287,13 +287,14 @@ def check_results(self, results, context, params, expected):
                     self.assertTrue(result_lyr, results[id])
 
                 compare = expected_result.get('compare', {})
+                pk = expected_result.get('pk', None)
 
                 if len(expected_lyrs) == 1:
-                    self.assertLayersEqual(expected_lyrs[0], result_lyr, compare=compare)
+                    self.assertLayersEqual(expected_lyrs[0], result_lyr, compare=compare, pk=pk)
                 else:
                     res = False
                     for l in expected_lyrs:
-                        if self.checkLayersEqual(l, result_lyr, compare=compare):
+                        if self.checkLayersEqual(l, result_lyr, compare=compare, pk=pk):
                             res = True
                             break
                     self.assertTrue(res, 'Could not find matching layer in expected results')

python/plugins/processing/tests/testdata/qgis_algorithm_tests.yaml

@@ -2501,6 +2501,10 @@ tests:
       OUTPUT:
         name: expected/stats_by_category.gml
         type: vector
+        pk: id2
+        compare:
+          fields:
+            fid: skip
 
 #  - algorithm: qgis:zonalstatistics
 #    name: simple zonal statistics

python/testing/__init__.py

@@ -54,6 +54,10 @@ def assertLayersEqual(self, layer_expected, layer_result, **kwargs):
         :keyword compare: A map of comparison options. e.g.
                          { fields: { a: skip, b: { precision: 2 }, geometry: { precision: 5 } }
                          { fields: { __all__: cast( str ) } }
+        :keyword pk: "Primary key" type field - used to match features
+        from the expected table to their corresponding features in the result table. If not specified
+        features are compared by their order in the layer (e.g. first feature compared with first feature,
+        etc)
         """
         self.checkLayersEqual(layer_expected, layer_result, True, **kwargs)
 
@@ -69,6 +73,10 @@ def checkLayersEqual(self, layer_expected, layer_result, use_asserts=False, **kw
         :keyword compare: A map of comparison options. e.g.
                          { fields: { a: skip, b: { precision: 2 }, geometry: { precision: 5 } }
                          { fields: { __all__: cast( str ) } }
+        :keyword pk: "Primary key" type field - used to match features
+        from the expected table to their corresponding features in the result table. If not specified
+        features are compared by their order in the layer (e.g. first feature compared with first feature,
+        etc)
         """
 
         try:
@@ -98,8 +106,14 @@ def checkLayersEqual(self, layer_expected, layer_result, use_asserts=False, **kw
         except KeyError:
             precision = 14
 
-        expected_features = sorted(layer_expected.getFeatures(request), key=lambda f: f.id())
-        result_features = sorted(layer_result.getFeatures(request), key=lambda f: f.id())
+        def sort_by_pk_or_fid(f):
+            if 'pk' in kwargs and kwargs['pk'] is not None:
+                return f[kwargs['pk']]
+            else:
+                return f.id()
+
+        expected_features = sorted(layer_expected.getFeatures(request), key=sort_by_pk_or_fid)
+        result_features = sorted(layer_result.getFeatures(request), key=sort_by_pk_or_fid)
 
         for feats in zip(expected_features, result_features):
             if feats[0].hasGeometry():