[Refactor] Creates Transform interface

Moves categorizer into transform module.
Puts the categorizer under unit tests.

pfbudget/core/manager.py

@@ -4,7 +4,6 @@ import pickle
 import webbrowser
 
 from pfbudget.common.types import Operation
-from pfbudget.core.categorizer import Categorizer
 from pfbudget.db.client import DbClient
 from pfbudget.db.model import (
     Bank,
@@ -28,6 +27,7 @@ from pfbudget.db.model import (
 from pfbudget.extract.nordigen import NordigenClient, NordigenCredentialsManager
 from pfbudget.extract.parsers import parse_data
 from pfbudget.extract.psd2 import PSD2Extractor
+from pfbudget.transform.categorizer import Categorizer
 
 
 class Manager:

pfbudget/transform/transform.py

@@ -0,0 +1,10 @@
+from abc import ABC, abstractmethod
+from typing import Sequence
+
+from pfbudget.db.model import Transaction
+
+
+class Transformer(ABC):
+    @abstractmethod
+    def transform(self, _: Sequence[Transaction]) -> Sequence[Transaction]:
+        raise NotImplementedError

tests/mocks/categories.py

@@ -0,0 +1,11 @@
+from decimal import Decimal
+
+from pfbudget.db.model import Category, CategoryRule
+
+category_null = Category("null", None, set())
+
+category_cat1 = Category(
+    "cat#1",
+    None,
+    {CategoryRule(None, None, "desc#1", None, None, None, Decimal(0), "cat#1")},
+)

tests/test_transform.py

@@ -0,0 +1,52 @@
+from datetime import date
+from decimal import Decimal
+
+import mocks.categories as mock
+
+from pfbudget.db.model import (
+    Bank,
+    BankTransaction,
+    CategorySelector,
+    Selector_T,
+    TransactionCategory,
+)
+from pfbudget.transform.categorizer import Categorizer
+
+
+class TestTransform:
+    def test_nullify(self):
+        transactions = [
+            BankTransaction(
+                date(2023, 1, 1), "", Decimal("-500"), Bank("Bank#1", "", "")
+            ),
+            BankTransaction(
+                date(2023, 1, 2), "", Decimal("500"), Bank("Bank#2", "", "")
+            ),
+        ]
+
+        for t in transactions:
+            assert not t.category
+
+        categorizer = Categorizer()
+        categorizer.rules(transactions, [mock.category_null], [])
+
+        for t in transactions:
+            assert t.category == TransactionCategory(
+                "null", CategorySelector(Selector_T.nullifier)
+            )
+
+    def test_categorize(self):
+        transactions = [
+            BankTransaction(date(2023, 1, 1), "desc#1", Decimal("-10"), "Bank#1")
+        ]
+
+        for t in transactions:
+            assert not t.category
+
+        categorizer = Categorizer()
+        categorizer.rules(transactions, [mock.category_cat1], [])
+
+        for t in transactions:
+            assert t.category == TransactionCategory(
+                "cat#1", CategorySelector(Selector_T.rules)
+            )