GUACAMOLE-221: Add CUnit tests for guac_strdup()

src/libguac/tests/Makefile.am

@@ -43,6 +43,7 @@ test_libguac_SOURCES =               \
     protocol/guac_protocol_version.c \
     socket/fd_send_instruction.c     \
     socket/nested_send_instruction.c \
+    string/strdup.c                  \
     string/strlcat.c                 \
     string/strlcpy.c                 \
     string/strljoin.c                \

src/libguac/tests/string/strdup.c

@@ -0,0 +1,49 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+#include <CUnit/CUnit.h>
+#include <guacamole/string.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+/**
+ * Source test string for copying.
+ */
+const char* source_string = "Mashing avocados.";
+
+/**
+ * A NULL string variable for copying to insure that NULL is copied properly.
+ */
+const char* null_string = NULL;
+
+/**
+ * Verify guac_strdup() behavior when the string is both NULL and not NULL.
+ */
+void test_string__strdup() {
+
+    /* Copy the strings. */
+    char* dest_string = guac_strdup(source_string);
+    char* null_copy = guac_strdup(null_string);
+    
+    /* Run the tests. */
+    CU_ASSERT_STRING_EQUAL(dest_string, "Mashing avocados.");
+    CU_ASSERT_PTR_NULL(null_copy);
+
+}