Add tests for null checks in DefaultRulesEngine

Refines c994ffb01a

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

@@ -37,7 +37,9 @@ import org.assertj.core.api.Assertions;
 import org.jeasy.rules.annotation.Action;
 import org.jeasy.rules.annotation.Condition;
 import org.jeasy.rules.annotation.Priority;
+import org.jeasy.rules.api.Facts;
 import org.jeasy.rules.api.RuleListener;
+import org.jeasy.rules.api.Rules;
 import org.jeasy.rules.api.RulesEngineListener;
 import org.jeasy.rules.api.RulesEngineParameters;
 import org.junit.After;
@@ -64,6 +66,26 @@ public class DefaultRulesEngineTest extends AbstractTest {
         annotatedRule = new AnnotatedRule();
     }
 
+    @Test(expected = NullPointerException.class)
+    public void whenFireRules_thenNullRulesShouldNotBeAccepted() {
+        rulesEngine.fire(null, new Facts());
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void whenFireRules_thenNullFactsShouldNotBeAccepted() {
+        rulesEngine.fire(new Rules(), null);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void whenCheckRules_thenNullRulesShouldNotBeAccepted() {
+        rulesEngine.check(null, new Facts());
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void whenCheckRules_thenNullFactsShouldNotBeAccepted() {
+        rulesEngine.check(new Rules(), null);
+    }
+
     @Test
     public void whenConditionIsTrue_thenActionShouldBeExecuted() throws Exception {
         // Given