[nus-cs2103-AY1718S1#51] Add unit tests to the Utils class (nus-cs210…

…3-AY1718S1#59)

* Add unit test for Utils class

* Update comments

test/java/seedu/addressbook/common/UtilsTest.java

@@ -0,0 +1,72 @@
+package seedu.addressbook.common;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Test;
+
+public class UtilsTest {
+    @Test
+    public void isAnyNull() {
+        // empty list
+        assertFalse(Utils.isAnyNull());
+
+        // Any non-empty list
+        assertFalse(Utils.isAnyNull(new Object(), new Object()));
+        assertFalse(Utils.isAnyNull("test"));
+        assertFalse(Utils.isAnyNull(""));
+
+        // non empty list with just one null at the beginning
+        assertTrue(Utils.isAnyNull((Object) null));
+        assertTrue(Utils.isAnyNull(null, "", new Object()));
+        assertTrue(Utils.isAnyNull(null, new Object(), new Object()));
+
+        // non empty list with nulls in the middle
+        assertTrue(Utils.isAnyNull(new Object(), null, null, "test"));
+        assertTrue(Utils.isAnyNull("", null, new Object()));
+
+        // non empty list with one null as the last element
+        assertTrue(Utils.isAnyNull("", new Object(), null));
+        assertTrue(Utils.isAnyNull(new Object(), new Object(), null));
+
+        // confirms nulls inside the list are not considered
+        List<Object> nullList = Arrays.asList((Object) null);
+        assertFalse(Utils.isAnyNull(nullList));
+    }
+
+    @Test
+    public void elementsAreUnique() throws Exception {
+        // empty list
+        assertAreUnique();
+
+        // only one object
+        assertAreUnique((Object) null);
+        assertAreUnique(1);
+        assertAreUnique("");
+        assertAreUnique("abc");
+
+        // all objects unique
+        assertAreUnique("abc", "ab", "a");
+        assertAreUnique(1, 2);
+
+        // some identical objects
+        assertNotUnique("abc", "abc");
+        assertNotUnique("abc", "", "abc", "ABC");
+        assertNotUnique("", "abc", "a", "abc");
+        assertNotUnique(1, new Integer(1));
+        assertNotUnique(null, 1, new Integer(1));
+        assertNotUnique(null, null);
+        assertNotUnique(null, "a", "b", null);
+    }
+
+    private void assertAreUnique(Object... objects) {
+        assertTrue(Utils.elementsAreUnique(Arrays.asList(objects)));
+    }
+
+    private void assertNotUnique(Object... objects) {
+        assertFalse(Utils.elementsAreUnique(Arrays.asList(objects)));
+    }
+}