AddressBook: remove unused containsTag()

AddressBook#containsTag() checks if the master list of Tags contains a
Tag with the same value as the given Tag.

AddressBook#containsTag() is not used in the production code. While it
is used in test code, its use can be replaced by
AddressBookTest#isTagObjectInAddressBookList().

Let's remove AddressBook#containsTag().

Notes:
* Why not keep AddressBook#containsTag() and remove
AddressBookTest#isTagObjectInAddressBookList() instead? The former does
a value equality test while the latter goes further and does a reference
equality test. The test code requires a reference equality test to
verify Person objects refer to Tag objects in the common tag list
instead of keeping its own copies of Tag objects.
* Why not change AddressBook#containsTag() to use reference equality and
use that in tests? Doing so will make AddressBook#containsTag()'s
semantics inconsistent with the rest of our API.

src/seedu/addressbook/data/AddressBook.java

@@ -90,13 +90,6 @@ public boolean containsPerson(ReadOnlyPerson key) {
         return allPersons.contains(key);
     }
 
-    /**
-     * Returns true if an equivalent person exists in the address book.
-     */
-    public boolean containsTag(Tag key) {
-        return allTags.contains(key);
-    }
-
     /**
      * Removes the equivalent person from the address book.
      *

test/java/seedu/addressbook/data/AddressBookTest.java

@@ -91,12 +91,9 @@ public void addPerson_emptyAddressBook() throws Exception {
 
     @Test
     public void addPerson_someTagsNotInTagList() throws Exception {
-        assertFalse(defaultAddressBook.containsTag(tagEconomist));
-        assertFalse(defaultAddressBook.containsTag(tagPrizeWinner));
+        assertFalse(isTagObjectInAddressBookList(tagEconomist, defaultAddressBook));
+        assertFalse(isTagObjectInAddressBookList(tagPrizeWinner, defaultAddressBook));
         defaultAddressBook.addPerson(davidElliot);
-        assertTrue(defaultAddressBook.containsTag(tagEconomist));
-        assertTrue(defaultAddressBook.containsTag(tagPrizeWinner));
-
         assertTrue(isTagObjectInAddressBookList(tagEconomist, defaultAddressBook));
         assertTrue(isTagObjectInAddressBookList(tagPrizeWinner, defaultAddressBook));
     }
@@ -117,7 +114,7 @@ public void addPerson_personAlreadyInListButHasTagNotInList_tagNotAdded() throws
             // ignore expected exception
         }
 
-        assertFalse(defaultAddressBook.containsTag(tagPrizeWinner));
+        assertFalse(isTagObjectInAddressBookList(tagPrizeWinner, defaultAddressBook));
     }
 
     @Test
@@ -139,25 +136,6 @@ public void containsPerson() throws Exception {
         }
     }
 
-    @Test
-    public void containsTag() throws Exception {
-        UniqueTagList tagsWhichShouldBeIn = new UniqueTagList(tagMathematician, tagScientist);
-        UniqueTagList tagsWHichShouldNotBeIn = new UniqueTagList(tagEconomist, tagPrizeWinner);
-
-        for (Tag tagWhichShouldBeIn : tagsWhichShouldBeIn) {
-            assertTrue(defaultAddressBook.containsTag(tagWhichShouldBeIn));
-        }
-        for (Tag tagWhichShouldNotBeIn : tagsWHichShouldNotBeIn) {
-            assertFalse(defaultAddressBook.containsTag(tagWhichShouldNotBeIn));
-        }
-
-        UniqueTagList allTags = new UniqueTagList(tagPrizeWinner, tagScientist, tagMathematician, tagEconomist);
-
-        for (Tag tag : allTags) {
-            assertFalse(emptyAddressBook.containsTag(tag));
-        }
-    }
-
     @Test
     public void removePerson_personExists_removesNormally() throws Exception {
         int numberOfPersonsBeforeRemoval = getSize(defaultAddressBook.getAllPersons());