Refactor shift constraints in tests to use new constraint classes

- Updated test cases in `test_workers.py` to replace dictionary-based constraints with instances of `PreShiftConstraint`, `PostShiftConstraint`, and `MaxShiftsPerWeekConstraint`.
- Added a new test `test_worker_assign_as_block_preference2` to verify worker preferences for block assignments.
- Marked tests as slow where appropriate to improve test suite performance.

test/test_nights2.py

@@ -1,6 +1,6 @@
 import datetime
 import pytest
-from rota.shifts import InvalidShift, NoWorkers, RotaBuilder, SingleShift, days
+from rota.shifts import InvalidShift, NightConstraint, NoWorkers, PostShiftConstraint, PreShiftConstraint, RotaBuilder, SingleShift, days
 from rota.workers import Worker
 
 def generate_basic_rota(weeks_to_rota=10):
@@ -35,7 +35,7 @@ def test_nights():
             length=12.5,
             days=days[5:],
             force_as_block=True,
-            constraint=[{"name": "night"}, {"name": "pre", "options": 2}],
+            constraints=[NightConstraint(), PreShiftConstraint(days=2)],
             workers_required=2,
         ),
         SingleShift(
@@ -60,7 +60,7 @@ def test_nights_pre3():
             length=12.5,
             days=days[5:],
             force_as_block=True,
-            constraint=[{"name": "night"}, {"name": "pre", "options": 3}],
+            constraints=[NightConstraint(), PreShiftConstraint(days=3)],
             workers_required=2,
         ),
         SingleShift(
@@ -84,7 +84,7 @@ def test_nights_pre3_2():
             length=12.5,
             days=days[5:],
             force_as_block=True,
-            constraint=[{"name": "night"}, {"name": "pre", "options": 3}],
+            constraints=[NightConstraint(), PreShiftConstraint(days=3)],
             workers_required=1,
         ),
         SingleShift(
@@ -108,7 +108,7 @@ def test_nights_fail():
             length=12.5,
             days=days[5:],
             force_as_block=True,
-            constraint=[{"name": "night"}, {"name": "pre", "options": 3}],
+            constraints=[NightConstraint(), PreShiftConstraint(days=3)],
             workers_required=2,
         ),
         SingleShift(
@@ -132,7 +132,7 @@ def test_nights2():
             length=12.5,
             days=days[5:],
             force_as_block=True,
-            constraint=[{"name": "night"}],
+            constraints=[NightConstraint()],
             workers_required=2,
         ),
         SingleShift(
@@ -158,10 +158,10 @@ def test_nights_pre_wrap_around():
             length=12.5,
             days=days[:2],
             force_as_block=True,
-            constraint=[
-                {"name": "night"},
-                {"name": "pre", "options": 5},
-                {"name": "post", "options": 5},
+            constraints=[
+                NightConstraint(),
+                PreShiftConstraint(days=5),
+                PostShiftConstraint(days=5),
             ],
             workers_required=3,
         ),
@@ -195,7 +195,7 @@ def test_nights_max_frequency():
             length=12.5,
             days=days[5:],
             force_as_block=True,
-            constraint=[{"name": "night"}],
+            constraints=[NightConstraint()],
             workers_required=2,
         ),
     )
@@ -213,7 +213,7 @@ def test_nights_max_frequency_fail():
             length=12.5,
             days=days[5:],
             force_as_block=True,
-            constraint=[{"name": "night"}],
+            constraints=[NightConstraint()],
             workers_required=2,
         ),
     )
@@ -230,7 +230,7 @@ def test_nights_max_frequency3():
             length=12.5,
             days=days[5:],
             force_as_block=True,
-            constraint=[{"name": "night"}],
+            constraints=[NightConstraint()],
             workers_required=1,
         ),
         SingleShift(
@@ -239,7 +239,7 @@ def test_nights_max_frequency3():
             length=12.5,
             days=days[:5],
             force_as_block=True,
-            constraint=[{"name": "night"}],
+            constraints=[NightConstraint()],
             workers_required=1,
         ),
     )
@@ -257,7 +257,7 @@ def test_nights_max_frequency4():
             length=12.5,
             days=days[5:],
             force_as_block=True,
-            constraint=[{"name": "night"}],
+            constraints=[NightConstraint()],
             workers_required=1,
         ),
         SingleShift(
@@ -266,7 +266,7 @@ def test_nights_max_frequency4():
             length=12.5,
             days=days[:5],
             force_as_block=True,
-            constraint=[{"name": "night"}],
+            constraints=[NightConstraint()],
             workers_required=1,
         ),
     )
@@ -291,7 +291,7 @@ def test_nights_max_frequency_exclusions():
             length=12.5,
             days=days[5:],
             force_as_block=True,
-            constraint=[{"name": "night"}],
+            constraints=[NightConstraint()],
             workers_required=2,
         ),
     )
@@ -310,7 +310,7 @@ def test_nights_max_frequency_exclusions2():
             length=12.5,
             days=days[5:],
             force_as_block=True,
-            constraint=[{"name": "night"}],
+            constraints=[NightConstraint()],
             workers_required=2,
         ),
     )
@@ -346,7 +346,7 @@ def test_nights_max_frequency_exclusions3():
             days=days[5:],
             force_as_block=True,
             balance_offset=10,
-            constraint=[{"name": "night"}],
+            constraints=[NightConstraint()],
             workers_required=2,
         ),
     )