migrated NullSchema to new ViolationException constructor

Author: erosb

core/src/main/java/org/everit/json/schema/NullSchema.java

@@ -22,8 +22,6 @@
  */
 public class NullSchema extends Schema {
 
-  public static final NullSchema INSTANCE = new NullSchema(builder());
-
   /**
    * Builder class for {@link NullSchema}.
    */
@@ -35,6 +33,8 @@ public NullSchema build() {
     }
   }
 
+  public static final NullSchema INSTANCE = new NullSchema(builder());
+
   public static Builder builder() {
     return new Builder();
   }
@@ -46,7 +46,8 @@ public NullSchema(final Builder builder) {
   @Override
   public void validate(final Object subject) {
     if (!(subject == null || subject == JSONObject.NULL)) {
-      throw new ValidationException("expected: null, found: " + subject.getClass().getSimpleName());
+      throw new ValidationException(this, "expected: null, found: "
+          + subject.getClass().getSimpleName());
     }
   }
 }

core/src/test/java/org/everit/json/schema/NullSchemaTest.java

@@ -15,16 +15,14 @@
  */
 package org.everit.json.schema;
 
-import org.everit.json.schema.NullSchema;
-import org.everit.json.schema.ValidationException;
 import org.json.JSONObject;
 import org.junit.Test;
 
 public class NullSchemaTest {
 
-  @Test(expected = ValidationException.class)
+  @Test
   public void failure() {
-    NullSchema.INSTANCE.validate("null");
+    TestSupport.exceptFailure(NullSchema.INSTANCE, "null");
   }
 
   @Test