add test for issue #139 (NPE If i add Fact with null value and use annotation)

easy-rules-core/src/test/java/org/jeasy/rules/core/NullFactAnnotationParameterTest.java

@@ -0,0 +1,48 @@
+package org.jeasy.rules.core;
+
+import org.jeasy.rules.annotation.Action;
+import org.jeasy.rules.annotation.Condition;
+import org.jeasy.rules.annotation.Fact;
+import org.jeasy.rules.annotation.Rule;
+import org.jeasy.rules.api.Facts;
+import org.jeasy.rules.api.Rules;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.Map;
+
+/**
+ * Null value in facts must be accepted, this is not same thing that fact missing
+ */
+public class NullFactAnnotationParameterTest extends AbstractTest {
+
+    @Test
+    public void testNullFact() {
+        Rules rules = new Rules();
+        rules.register(new AnnotatedParametersRule());
+
+        Facts facts = new Facts();
+        facts.put("fact1", new Object());
+        facts.put("fact2", null);
+
+        Map<org.jeasy.rules.api.Rule, Boolean> results = rulesEngine.check(rules, facts);
+
+        for (boolean b : results.values()) {
+            Assert.assertTrue(b);
+        }
+    }
+
+    @Rule
+    public class AnnotatedParametersRule {
+
+        @Condition
+        public boolean when(@Fact("fact1") Object fact1, @Fact("fact2") Object fact2) {
+            return true;
+        }
+
+        @Action
+        public void then(@Fact("fact1") Object fact1, @Fact("fact2") Object fact2) {
+        }
+
+    }
+}