Minor test cleanup changes.

tests/__init__.py

@@ -605,6 +605,7 @@ def get_checksum_cls(algorithm=DEFAULT_CHECKSUM_ALGORITHM.lower()):
     This pass through is grabbing our internally supported list of checksums
     to ensure we stay in sync, while not exposing them publicly.
 
-    Returns the default checksum algorithm class if none is specified.
+    Returns a checksum algorithm class. The default checksum class is used
+    if one isn't specified.
     """
     return _CHECKSUM_CLS[algorithm]

tests/unit/test_handlers.py

@@ -2006,7 +2006,7 @@ def test_request_validation_mode_member_when_required(
     assert "ChecksumMode" not in params
 
 
-def test_request_validation_mode_member_is_not_enabled(
+def test_request_validation_mode_member_set_by_user(
     checksum_operation_model,
 ):
     params = {"ChecksumMode": "FAKE_VALUE"}

tests/unit/test_httpchecksum.py

@@ -35,7 +35,7 @@
     resolve_request_checksum_algorithm,
     resolve_response_checksum_algorithms,
 )
-from botocore.model import OperationModel, StringShape
+from botocore.model import OperationModel, StringShape, StructureShape
 from tests import get_checksum_cls, mock, requires_crt
 
 
@@ -57,6 +57,7 @@ def _make_operation_model(
         if http_checksum and "requestAlgorithmMember" in http_checksum:
             shape = mock.Mock(spec=StringShape)
             shape.serialization = {"name": "x-amz-request-algorithm"}
+            operation.input_shape = mock.Mock(spec=StructureShape)
             operation.input_shape.members = {
                 http_checksum["requestAlgorithmMember"]: shape
             }
@@ -127,6 +128,9 @@ def test_request_checksum_algorithm_model_default(self):
         }
         actual_algorithm = request["context"]["checksum"]["request_algorithm"]
         self.assertEqual(actual_algorithm, expected_algorithm)
+        self.assertEqual(
+            request["headers"]["x-amz-request-algorithm"], "CRC32"
+        )
 
         # Param is present, sha256 checksum will be set
         params = {"Algorithm": "sha256"}
@@ -164,6 +168,9 @@ def test_request_checksum_algorithm_model_default_streaming(self):
         }
         actual_algorithm = request["context"]["checksum"]["request_algorithm"]
         self.assertEqual(actual_algorithm, expected_algorithm)
+        self.assertEqual(
+            request["headers"]["x-amz-request-algorithm"], "CRC32"
+        )
 
         # Param is present, sha256 checksum will be set in the trailer
         params = {"Algorithm": "sha256"}