Added RET keyword

tests/evaluators/test_RetEvaluator.py

@@ -0,0 +1,46 @@
+import pytest
+from core.builtin_concepts import ReturnValueConcept
+from core.concept import Concept
+from evaluators.RetEvaluator import RetEvaluator
+
+from tests.BaseTest import BaseTest
+from tests.TestUsingMemoryBasedSheerka import TestUsingMemoryBasedSheerka
+
+
+class TestRetEvaluator(TestUsingMemoryBasedSheerka):
+
+    @pytest.mark.parametrize("ret_val, expected", [
+        (ReturnValueConcept("who", True, Concept("foo", ret="bar")), True),
+        (ReturnValueConcept("who", False, Concept("foo", ret="bar")), False),
+        (ReturnValueConcept("who", True, Concept("foo")), False),
+        (BaseTest.pretval(Concept("foo", ret="bar")), False),
+        (ReturnValueConcept("who", True, "not even a concept"), False),
+    ])
+    def test_i_can_match(self, ret_val, expected):
+        context = self.get_context()
+        assert RetEvaluator().matches(context, ret_val) == expected
+
+    def test_i_can_evaluate_fully_initialized(self):
+        sheerka, context, foo, the_concept = self.init_concepts("foo", Concept("the concept", ret="a").def_var("a"))
+
+        instance = sheerka.new("the concept")
+        instance.set_value("a", sheerka.new("foo"))
+        ret_value = self.tretval(sheerka, instance)
+
+        res = RetEvaluator().eval(context, ret_value)
+        assert res.status
+        assert sheerka.isinstance(res.body, "foo")
+
+    @pytest.mark.parametrize("instance, expected", [
+        (Concept("with ret", ret="a").def_var("a", "foo"), "foo"),
+        (Concept("with ret", ret="a", body="10").def_var("a", "foo"), "foo"),
+        (Concept("with ret", ret="a").def_var("a", "bar"), "bar"),
+    ])
+    def test_i_can_evaluate(self, instance, expected):
+        sheerka, context, foo, bar = self.init_concepts("foo", Concept("bar", body="10"))
+
+        ret_value = self.tretval(sheerka, instance)
+
+        res = RetEvaluator().eval(context, ret_value)
+        assert res.status
+        assert sheerka.isinstance(res.body, expected)