Unit test cumulative resistance with a max_value

A surprising result on 1.18, the max_value attributes get added together.

In 1.19, 82499d0785 changes this to something
logical, using `min(each individual max_value)` and disregarding the cumulative
attributes.

data/test/scenarios/wml_tests/UnitsWML/AbilitiesWML/resistance/resistance_cumulative_max_value.cfg

@@ -0,0 +1,37 @@
+# wmllint: no translatables
+
+#####
+# API(s) being tested: [resistance]cumulative=
+##
+# Actions:
+# Give all units 20% resistance to all damage types with max_value=15 and cumulative=yes
+# Give all units 30% resistance to all damage types with max_value=17 and cumulative=yes
+# Give all units 20% resistance to all damage types with max_value=15 and cumulative=yes
+# All abilities have unique ids
+# Attack each other
+##
+# Expected end state:
+# In 1.18, the cumulative effect is 30% resistance with a max_value of 47.
+# The damage from the attack is reduced by 30%
+#####
+{COMMON_KEEP_A_B_UNIT_TEST "resistance_cumulative_max_value" (
+    [event]
+        name = start
+
+        [modify_unit]
+            [filter]
+            [/filter]
+            [effect]
+                apply_to = new_ability
+                [abilities]
+                    {TEST_ABILITY resistance 20 (max_value=15) ID=1 CUMULATIVE=yes SELF=yes}
+                    {TEST_ABILITY resistance 30 (max_value=17) ID=2 CUMULATIVE=yes SELF=yes}
+                    {TEST_ABILITY resistance 20 (max_value=15) ID=3 CUMULATIVE=yes SELF=yes}
+                [/abilities]
+            [/effect]
+        [/modify_unit]
+
+        {ATTACK_AND_VALIDATE 70}
+        {SUCCEED}
+    [/event]
+)}

wml_test_schedule

@@ -602,6 +602,7 @@
 0 resistance_two_cumulative_mixed_unique_id
 0 resistance_two_cumulative_mixed_unique_id_skeletal
 0 resistance_max_value
+0 resistance_cumulative_max_value
 0 resistance_negative_max_value
 0 resistance_apply_to_blade
 0 resistance_apply_to_non_blade