Raise error if csp estimate is not of proper type

tests/models/test_task_order.py

@@ -1,6 +1,11 @@
+from werkzeug.datastructures import FileStorage
+import pytest
+
+from atst.models.attachment import Attachment
 from atst.models.task_order import TaskOrder, Status
 
 from tests.factories import random_future_date, random_past_date
+from tests.mocks import PDF_FILENAME
 
 
 class TestTaskOrderStatus:
@@ -30,3 +35,26 @@ def test_is_submitted():
 
     to = TaskOrder(number="42")
     assert to.is_submitted
+
+
+class TestCSPEstimate:
+    def test_setting_estimate_with_attachment(self):
+        to = TaskOrder()
+        attachment = Attachment(filename="sample.pdf", object_name="sample")
+        to.csp_estimate = attachment
+
+        assert to.attachment_id == attachment.id
+
+    def test_setting_estimate_with_file_storage(self):
+        to = TaskOrder()
+        with open(PDF_FILENAME, "rb") as fp:
+            fs = FileStorage(fp, content_type="application/pdf")
+            to.csp_estimate = fs
+
+        assert to.csp_estimate is not None
+        assert to.csp_estimate.filename == PDF_FILENAME
+
+    def test_setting_estimate_with_invalid_object(self):
+        to = TaskOrder()
+        with pytest.raises(TypeError):
+            to.csp_estimate = "invalid"