Add unit tests for Lua API wesnoth.simulate_combat

(cherry picked from commit d96968b2ec)

data/test/scenarios/simulate_combat_clone_adjacent.cfg

@@ -0,0 +1,39 @@
+# wmllint: no translatables
+
+#####
+# API(s) being tested: wesnoth.simulate_combat
+##
+# Actions:
+# Start with Alice and Bob on separate keeps (the GENERIC_UNIT_TEST macro).
+# Make a private-to-Lua clone of Alice, move her next to Bob.
+# Simulate combat.
+##
+# Expected end state:
+# The simulation with the original Alice shows that neither can reach the other.
+# The simulation with the cloned Alice shows combat stats.
+#####
+{GENERIC_UNIT_TEST simulate_combat_clone_adjacent (
+    [event]
+        name=start
+
+        [lua]
+            code=<<
+                local alice = wesnoth.units.find({id="alice"})[1]
+                local bob = wesnoth.units.find({id="bob"})[1]
+                local clone_alice = alice:clone()
+                clone_alice.x = bob.x
+                clone_alice.y = bob.y + 1
+
+                local att_stats, def_stats = wesnoth.simulate_combat(clone_alice, bob)
+                unit_test.assert_approx_equal(att_stats.untouched, 1.0, 0.01, "Alice should have used her ranged attack")
+                unit_test.assert_approx_equal(def_stats.untouched, 0.6 ^ 4, 0.01, "Bob should be on 60% def")
+
+                att_stats, def_stats = wesnoth.simulate_combat(alice, bob)
+                unit_test.assert_approx_equal(att_stats.untouched, 1.0, 0.01, "Alice should be out of reach of combat")
+                unit_test.assert_approx_equal(def_stats.untouched, 1.0, 0.01, "Bob should be out of reach of combat")
+            >>
+        [/lua]
+
+        {SUCCEED}
+    [/event]
+)}

data/test/scenarios/simulate_combat_occupied.cfg

@@ -0,0 +1,55 @@
+#textdomain wesnoth-test
+
+#####
+# API(s) being tested: wesnoth.simulate_combat
+##
+# Actions:
+# Start with Alice and Bob on separate keeps (the GENERIC_UNIT_TEST macro).
+# Spawn a unit called Dave on Bob's side next to Bob.
+# Make a private-to-Lua clone of Alice.
+# Simulate combat as if Alice was on the hex occupied by Dave.
+# While the units are in place, simulate combat between Dave and Bob too.
+##
+# Expected end state:
+# The simulation for Alice shows the same stats as if the hex was unoccupied.
+#
+# The simulation for Dave allows the fight to happen, and doesn't log any
+# errors. Possibly something that should change, but the test is included to
+# check for API changes in 1.16.
+#####
+{GENERIC_UNIT_TEST simulate_combat_occupied (
+    [event]
+        name=start
+
+        [unit]
+            side=2
+            name=_ "Dave"
+            type=Orcish Grunt
+            id=dave
+            placement=leader
+        [/unit]
+
+        [lua]
+            code=<<
+                local alice = wesnoth.units.find({id="alice"})[1]
+                local bob = wesnoth.units.find({id="bob"})[1]
+                local dave = wesnoth.units.find({id="dave"})[1]
+                local clone_alice = alice:clone()
+                clone_alice.x = dave.x
+                clone_alice.y = dave.y
+
+                local att_stats, def_stats = wesnoth.simulate_combat(clone_alice, bob)
+                unit_test.assert_approx_equal(att_stats.untouched, 1.0, 0.01, "Alice should have used her ranged attack")
+                unit_test.assert_approx_equal(def_stats.untouched, 0.6 ^ 4, 0.01, "Bob should be on 60% def")
+
+                -- While the test is set up, check what happens if Dave attacks his own leader.
+                -- In 1.16.x and at least 1.17.2 the attack gets simulated as if they were on different sides.
+                att_stats, def_stats = wesnoth.simulate_combat(dave, bob)
+                unit_test.assert_approx_equal(att_stats.untouched, 0.4 ^ 2, 0.01, "Dave should have attacked from 40% def")
+                unit_test.assert_approx_equal(def_stats.untouched, 0.6 ^ 2, 0.01, "Bob should have retaliated from 60% def")
+            >>
+        [/lua]
+
+        {SUCCEED}
+    [/event]
+)}

wml_test_schedule

@@ -358,3 +358,5 @@
 0 lua_map_find
 0 mapgen_filter_range
 0 mapgen_filter_terrain
+0 simulate_combat_clone_adjacent
+0 simulate_combat_occupied