add sanity checks

easy-rules-core/src/main/java/org/jeasy/rules/api/Facts.java

@@ -46,6 +46,7 @@ public class Facts implements Iterable<Map.Entry<String, Object>> {
      */
     @Deprecated
     public void add(String name, Object fact) {
+        Objects.requireNonNull(name);
         facts.put(name, fact);
     }
 
@@ -57,6 +58,7 @@ public class Facts implements Iterable<Map.Entry<String, Object>> {
      * @param fact object to put in the working memory
      */
     public void put(String name, Object fact) {
+        Objects.requireNonNull(name);
         facts.put(name, fact);
     }
 
@@ -66,6 +68,7 @@ public class Facts implements Iterable<Map.Entry<String, Object>> {
      * @param name of fact to remove
      */
     public void remove(String name) {
+        Objects.requireNonNull(name);
         facts.remove(name);
     }
 
@@ -76,6 +79,7 @@ public class Facts implements Iterable<Map.Entry<String, Object>> {
      * @return the fact having the given name, or null if there is no fact with the given name
      */
     public Object get(String name) {
+        Objects.requireNonNull(name);
         return facts.get(name);
     }
 

easy-rules-core/src/main/java/org/jeasy/rules/api/Rules.java

@@ -25,10 +25,7 @@ package org.jeasy.rules.api;
 
 import org.jeasy.rules.core.RuleProxy;
 
-import java.util.Collections;
-import java.util.Iterator;
-import java.util.Set;
-import java.util.TreeSet;
+import java.util.*;
 
 /**
  * This class encapsulates a set of rules and represents a rules namespace.
@@ -75,6 +72,7 @@ public class Rules implements Iterable<Rule> {
      * @param rule to register
      */
     public void register(Object rule) {
+        Objects.requireNonNull(rule);
         rules.add(RuleProxy.asRule(rule));
     }
 
@@ -84,6 +82,7 @@ public class Rules implements Iterable<Rule> {
      * @param rule to unregister
      */
     public void unregister(Object rule) {
+        Objects.requireNonNull(rule);
         rules.remove(RuleProxy.asRule(rule));
     }
 
@@ -93,6 +92,7 @@ public class Rules implements Iterable<Rule> {
      * @param ruleName the name of the rule to unregister
      */
     public void unregister(final String ruleName){
+        Objects.requireNonNull(ruleName);
         Rule rule = findRuleByName(ruleName);
         if(rule != null) {
             unregister(rule);

easy-rules-core/src/test/java/org/jeasy/rules/api/FactsTest.java

@@ -54,4 +54,23 @@ public class FactsTest {
         assertThat(facts.get("foo")).isEqualTo(1);
     }
 
+    @Test(expected = NullPointerException.class)
+    public void addingNullFactsIsNotAllowed() throws Exception {
+        facts.add(null, "foo");
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void whenPutNullFact_thenShouldThrowNullPointerException() throws Exception {
+        facts.put(null, "foo");
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void whenRemoveNullFact_thenShouldThrowNullPointerException() throws Exception {
+        facts.remove(null);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void whenGetNullFact_thenShouldThrowNullPointerException() throws Exception {
+        facts.get(null);
+    }
 }

easy-rules-core/src/test/java/org/jeasy/rules/api/RulesTest.java

@@ -93,6 +93,16 @@ public class RulesTest {
         assertThat(rules).isEmpty();
     }
 
+    @Test(expected = NullPointerException.class)
+    public void whenRegisterNullRule_thenShouldThrowNullPointerException() throws Exception {
+        rules.register(null);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void whenUnregisterNullRule_thenShouldThrowNullPointerException() throws Exception {
+        rules.unregister(null);
+    }
+
     @org.jeasy.rules.annotation.Rule
     class DummyRule {
         @Condition