[W6.4d][W15-B4]Muhammad Nur Kamal

src/seedu/addressbook/commands/AddCommand.java

@@ -66,5 +66,9 @@ public CommandResult execute() {
             return new CommandResult(MESSAGE_DUPLICATE_PERSON);
         }
     }
-
+
+    @Override
+    public boolean isMutating() {
+        return true;
+    }
 }

src/seedu/addressbook/commands/ClearCommand.java

@@ -16,4 +16,9 @@ public CommandResult execute() {
         addressBook.clear();
         return new CommandResult(MESSAGE_SUCCESS);
     }
+
+    @Override
+    public boolean isMutating() {
+        return true;
+    }
 }

src/seedu/addressbook/commands/Command.java

@@ -70,4 +70,11 @@ public int getTargetIndex() {
     public void setTargetIndex(int targetIndex) {
         this.targetIndex = targetIndex;
     }
+
+    /**
+     * Checks if command is able to modify data by Command type.
+     */
+    public boolean isMutating() {
+        return false;
+    }
 }

src/seedu/addressbook/commands/DeleteCommand.java

@@ -39,4 +39,8 @@ public CommandResult execute() {
         }
     }
 
+    @Override
+    public boolean isMutating() {
+        return true;
+    }
 }

src/seedu/addressbook/logic/Logic.java

@@ -85,7 +85,9 @@ public CommandResult execute(String userCommandText) throws Exception {
     private CommandResult execute(Command command) throws Exception {
         command.setData(addressBook, lastShownList);
         CommandResult result = command.execute();
-        storage.save(addressBook);
+        if(command.isMutating()) {
+            storage.save(addressBook);
+        }
         return result;
     }
 

test/java/seedu/addressbook/logic/LogicTest.java

@@ -12,6 +12,7 @@
 import seedu.addressbook.data.person.*;
 import seedu.addressbook.data.tag.Tag;
 import seedu.addressbook.data.tag.UniqueTagList;
+import seedu.addressbook.parser.Parser;
 import seedu.addressbook.storage.StorageFile;
 
 import java.util.*;
@@ -76,9 +77,14 @@ private void assertCommandBehavior(String inputCommand,
                                       AddressBook expectedAddressBook,
                                       boolean isRelevantPersonsExpected,
                                       List<? extends ReadOnlyPerson> lastShownList) throws Exception {
-
+        Command command = new Parser().parseCommand(inputCommand);
         //Execute the command
         CommandResult r = logic.execute(inputCommand);
+
+        //Guarantees saveFile is saved for non-mutating methods
+        if (!command.isMutating()) {
+            saveFile.save(addressBook);
+        }
 
         //Confirm the result contains the right data
         assertEquals(expectedMessage, r.feedbackToUser);