[ONOS-3878, 3876, 3879] Yang Parser Manager with Stack and Error Validation

Change-Id: I10e68bd676eca4d576de1234fbb67026c7b49939
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/YangUtilsParserManagerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/YangUtilsParserManagerTest.java
new file mode 100644
index 0000000..f8a6120
--- /dev/null
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/YangUtilsParserManagerTest.java
@@ -0,0 +1,103 @@
+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * 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 org.onosproject.yangutils.parser.impl;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+
+/**
+ * Test case for testing YANG utils parser manager.
+ */
+public class YangUtilsParserManagerTest {
+
+    YangUtilsParserManager manager = new YangUtilsParserManager();
+    File file;
+    BufferedWriter out;
+
+    @Before
+    public void setUp() throws Exception {
+        file = new File("demo.yang");
+        out = new BufferedWriter(new FileWriter(file));
+    }
+    @After
+    public void tearDown() throws Exception {
+        file.delete();
+    }
+
+    /**
+     * This test case checks whether the null pointer exception is generated
+     * when the input YANG file is null.
+     */
+    @Test(expected = NullPointerException.class)
+    public void getDataModelNullFileTest() throws IOException, ParserException {
+        YangUtilsParserManager manager = new YangUtilsParserManager();
+        YangNode node = manager.getDataModel(null);
+    }
+
+    /**
+     * This test case checks whether the io exception is generated
+     * when the input YANG file is non existent.
+     */
+    @Test(expected = IOException.class)
+    public void getDataModelNonExistentFileTest() throws IOException, ParserException {
+
+        YangUtilsParserManager manager = new YangUtilsParserManager();
+        YangNode node = manager.getDataModel("nonexistent.yang");
+    }
+
+    /**
+     * This test case checks if the input YANG file is correct no exception
+     * should be generated.
+     */
+    @Test
+    public void getDataModelCorrectFileTest() throws IOException, ParserException {
+
+        out.write("module ONOS {\n");
+        out.write("yang-version 1;\n");
+        out.write("namespace urn:ietf:params:xml:ns:yang:ietf-ospf;\n");
+        out.write("prefix On;\n");
+        out.write("}\n");
+        out.close();
+
+        YangNode node = manager.getDataModel("demo.yang");
+    }
+
+    /**
+     * This test case checks if the input YANG file with wrong YANG constructs
+     * than parser exception should be generated.
+     */
+    @Test(expected = ParserException.class)
+    public void getDataModelIncorrectFileTest() throws IOException, ParserException {
+
+        out.write("module ONOS {\n");
+        out.write("yang-version 1\n");
+        out.write("namespace urn:ietf:params:xml:ns:yang:ietf-ospf;\n");
+        out.write("prefix On;\n");
+        out.write("}\n");
+        out.close();
+
+        YangNode node = manager.getDataModel("demo.yang");
+    }
+}
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