Add test which ensures bad source freshness checks raise appropriate …

…error

This test directly tests that when a source freshness check doesn't have a
`loaded_at_field` and the adapter in use doesn't support metadata checks,
then the appropriate error message gets raised. That is, it directly tests
the change made in a162d53. This test indirectly tests the changes in both
7ec2f82 and 7b0ff31 as the appropriate error can only be raised because
we've fixed other upstream issues via those commits.

tests/functional/sources/test_source_freshness.py

@@ -5,6 +5,8 @@
 import yaml
 
 import dbt.version
+from dbt.artifacts.schemas.freshness import FreshnessResult
+from dbt.artifacts.schemas.results import FreshnessStatus
 from dbt.cli.main import dbtRunner
 from tests.functional.sources.common_source_setup import BaseSourcesTest
 from tests.functional.sources.fixtures import (
@@ -385,7 +387,7 @@ class TestMetadataFreshnessFails:
     def models(self):
         return {"schema.yml": freshness_via_metadata_schema_yml}
 
-    def test_metadata_freshness_fails(self, project):
+    def test_metadata_freshness_unsupported_parse_warning(self, project):
         """Since the default test adapter (postgres) does not support metadata
         based source freshness checks, trying to use that mechanism should
         result in a parse-time warning."""
@@ -401,6 +403,16 @@ def warning_probe(e):
 
         assert got_warning
 
+    def test_metadata_freshness_unsupported_error_when_run(self, project):
+
+        runner = dbtRunner()
+        result = runner.invoke(["source", "freshness"])
+        assert isinstance(result.result, FreshnessResult)
+        assert len(result.result.results) == 1
+        freshness_result = result.result.results[0]
+        assert freshness_result.status == FreshnessStatus.RuntimeErr
+        assert "Could not compute freshness for source test_table" in freshness_result.message
+
 
 class TestHooksInSourceFreshness(SuccessfulSourceFreshnessTest):
     @pytest.fixture(scope="class")