add base class for merge exclude tests (#6700)

* add base class for merge exclude tests

* changie <33

* remove comments

* add comments to sql, remove and clarify contents of resultholder

.changes/unreleased/Fixes-20230123-132814.yaml

@@ -0,0 +1,6 @@
+kind: Fixes
+body: add merge_exclude_columns adapter tests
+time: 2023-01-23T13:28:14.808748-06:00
+custom:
+  Author: dave-connors-3
+  Issue: "6699"

tests/adapter/dbt/tests/adapter/incremental/test_incremental_merge_exclude_columns.py

@@ -0,0 +1,116 @@
+import pytest
+from dbt.tests.util import run_dbt, check_relations_equal
+from collections import namedtuple
+
+
+models__merge_exclude_columns_sql = """
+{{ config(
+    materialized = 'incremental',
+    unique_key = 'id',
+    incremental_strategy='merge',
+    merge_exclude_columns=['msg']
+) }}
+
+{% if not is_incremental() %}
+
+-- data for first invocation of model
+
+select 1 as id, 'hello' as msg, 'blue' as color
+union all
+select 2 as id, 'goodbye' as msg, 'red' as color
+
+{% else %}
+
+-- data for subsequent incremental update
+
+select 1 as id, 'hey' as msg, 'blue' as color
+union all
+select 2 as id, 'yo' as msg, 'green' as color
+union all
+select 3 as id, 'anyway' as msg, 'purple' as color
+
+{% endif %}
+"""
+
+seeds__expected_merge_exclude_columns_csv = """id,msg,color
+1,hello,blue
+2,goodbye,green
+3,anyway,purple
+"""
+
+ResultHolder = namedtuple(
+    "ResultHolder",
+    [
+        "seed_count",
+        "model_count",
+        "seed_rows",
+        "inc_test_model_count",
+        "relation",
+    ],
+)
+
+
+class BaseMergeExcludeColumns:
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {"merge_exclude_columns.sql": models__merge_exclude_columns_sql}
+
+    @pytest.fixture(scope="class")
+    def seeds(self):
+        return {"expected_merge_exclude_columns.csv": seeds__expected_merge_exclude_columns_csv}
+
+    def update_incremental_model(self, incremental_model):
+        """update incremental model after the seed table has been updated"""
+        model_result_set = run_dbt(["run", "--select", incremental_model])
+        return len(model_result_set)
+
+    def get_test_fields(self, project, seed, incremental_model, update_sql_file):
+
+        seed_count = len(run_dbt(["seed", "--select", seed, "--full-refresh"]))
+
+        model_count = len(run_dbt(["run", "--select", incremental_model, "--full-refresh"]))
+
+        relation = incremental_model
+        # update seed in anticipation of incremental model update
+        row_count_query = "select * from {}.{}".format(project.test_schema, seed)
+
+        seed_rows = len(project.run_sql(row_count_query, fetch="all"))
+
+        # propagate seed state to incremental model according to unique keys
+        inc_test_model_count = self.update_incremental_model(incremental_model=incremental_model)
+
+        return ResultHolder(seed_count, model_count, seed_rows, inc_test_model_count, relation)
+
+    def check_scenario_correctness(self, expected_fields, test_case_fields, project):
+        """Invoke assertions to verify correct build functionality"""
+        # 1. test seed(s) should build afresh
+        assert expected_fields.seed_count == test_case_fields.seed_count
+        # 2. test model(s) should build afresh
+        assert expected_fields.model_count == test_case_fields.model_count
+        # 3. seeds should have intended row counts post update
+        assert expected_fields.seed_rows == test_case_fields.seed_rows
+        # 4. incremental test model(s) should be updated
+        assert expected_fields.inc_test_model_count == test_case_fields.inc_test_model_count
+        # 5. result table should match intended result set (itself a relation)
+        check_relations_equal(
+            project.adapter, [expected_fields.relation, test_case_fields.relation]
+        )
+
+    def test__merge_exclude_columns(self, project):
+        """seed should match model after two incremental runs"""
+
+        expected_fields = ResultHolder(
+            seed_count=1,
+            model_count=1,
+            inc_test_model_count=1,
+            seed_rows=3,
+            relation="expected_merge_exclude_columns",
+        )
+
+        test_case_fields = self.get_test_fields(
+            project,
+            seed="expected_merge_exclude_columns",
+            incremental_model="merge_exclude_columns",
+            update_sql_file=None,
+        )
+        self.check_scenario_correctness(expected_fields, test_case_fields, project)