fix(test): jacoco fails on Parameter coverage

Add missing Parameter unit test

Closes #51

nodes/src/test/java/io/aexp/nodes/graphql/ParameterTest.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2018 American Express Travel Related Services Company, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package io.aexp.nodes.graphql;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import org.junit.Test;
+
+public class ParameterTest {
+
+    @Test
+    public void parameterGetterTest() {
+        Parameter<Object> parameter = new Parameter<Object>(null, null);
+        assertNull(parameter.getKey());
+        assertNull(parameter.getValue());
+    }
+
+    @Test
+    public void parameterSetterTest() {
+        String key = "key";
+        Object value = new Object();
+        Parameter<Object> parameter = new Parameter<Object>(null, null);
+        parameter.setKey(key);
+        parameter.setValue(value);
+        assertEquals(key, parameter.getKey());
+        assertEquals(value, parameter.getValue());
+    }
+
+}