Move Spreadsheet models tests into own file

Previously this class was in app/utils.py, so it made sense for the
tests to be in "utils/test_csv.py". Since the class is now a proper
model [1], we can also move the tests into their own file.

[1]: 2c46d023da (diff-ac7b8d56e509c921efaadb5a776e1c9037531c4d2af78787f06f67a1f3533ae4)

tests/app/models/test_spreadsheet.py

@@ -0,0 +1,42 @@
+from collections import OrderedDict
+from pathlib import Path
+
+import pytest
+
+from app.models.spreadsheet import Spreadsheet
+
+
+def test_can_create_spreadsheet_from_large_excel_file():
+    with open(str(Path.cwd() / 'tests' / 'spreadsheet_files' / 'excel 2007.xlsx'), 'rb') as xl:
+        ret = Spreadsheet.from_file(xl, filename='xl.xlsx')
+    assert ret.as_csv_data
+
+
+def test_can_create_spreadsheet_from_dict():
+    assert Spreadsheet.from_dict(OrderedDict(
+        foo='bar',
+        name='Jane',
+    )).as_csv_data == (
+        "foo,name\r\n"
+        "bar,Jane\r\n"
+    )
+
+
+def test_can_create_spreadsheet_from_dict_with_filename():
+    assert Spreadsheet.from_dict({}, filename='empty.csv').as_dict['file_name'] == "empty.csv"
+
+
+@pytest.mark.parametrize('args, kwargs', (
+    (
+        ('hello', ['hello']),
+        {},
+    ),
+    (
+        (),
+        {'csv_data': 'hello', 'rows': ['hello']}
+    ),
+))
+def test_spreadsheet_checks_for_bad_arguments(args, kwargs):
+    with pytest.raises(TypeError) as exception:
+        Spreadsheet(*args, **kwargs)
+    assert str(exception.value) == 'Spreadsheet must be created from either rows or CSV data'

tests/app/utils/test_csv.py

@@ -1,15 +1,10 @@
-from collections import OrderedDict, namedtuple
+from collections import namedtuple
 from csv import DictReader
 from io import StringIO
-from pathlib import Path
 
 import pytest
 
-from app.utils.csv import (
-    Spreadsheet,
-    generate_notifications_csv,
-    get_errors_for_csv,
-)
+from app.utils.csv import generate_notifications_csv, get_errors_for_csv
 from tests.conftest import fake_uuid
 
 
@@ -79,42 +74,6 @@ def _get_notifications_csv_mock(
     )
 
 
-def test_can_create_spreadsheet_from_large_excel_file():
-    with open(str(Path.cwd() / 'tests' / 'spreadsheet_files' / 'excel 2007.xlsx'), 'rb') as xl:
-        ret = Spreadsheet.from_file(xl, filename='xl.xlsx')
-    assert ret.as_csv_data
-
-
-def test_can_create_spreadsheet_from_dict():
-    assert Spreadsheet.from_dict(OrderedDict(
-        foo='bar',
-        name='Jane',
-    )).as_csv_data == (
-        "foo,name\r\n"
-        "bar,Jane\r\n"
-    )
-
-
-def test_can_create_spreadsheet_from_dict_with_filename():
-    assert Spreadsheet.from_dict({}, filename='empty.csv').as_dict['file_name'] == "empty.csv"
-
-
-@pytest.mark.parametrize('args, kwargs', (
-    (
-        ('hello', ['hello']),
-        {},
-    ),
-    (
-        (),
-        {'csv_data': 'hello', 'rows': ['hello']}
-    ),
-))
-def test_spreadsheet_checks_for_bad_arguments(args, kwargs):
-    with pytest.raises(TypeError) as exception:
-        Spreadsheet(*args, **kwargs)
-    assert str(exception.value) == 'Spreadsheet must be created from either rows or CSV data'
-
-
 @pytest.mark.parametrize('created_by_name, expected_content', [
     (
         None, [