Add StatisticsTest

src/main/java/seedu/address/model/statistics/Statistics.java

@@ -4,10 +4,12 @@
 import java.util.ArrayList;
 
 import javafx.collections.transformation.FilteredList;
-import seedu.address.model.attributes.Category;
 import seedu.address.model.attributes.Date;
 import seedu.address.model.attributes.Frequency;
 import seedu.address.model.expense.Expense;
+
+import static java.util.Objects.requireNonNull;
+
 /**
  * Statistics
  */
@@ -26,8 +28,6 @@ public class Statistics {
     public static final int OTHERS = 8;
     public static final int ALL = 9;
 
-
-    protected Category category;
     protected String html;
     protected FilteredList<Expense> statsExpenses;
 
@@ -36,6 +36,7 @@ public class Statistics {
      * statsExpense must be present and not null.
      */
     public Statistics(FilteredList<Expense> statsExpenses) {
+        requireNonNull(statsExpenses);
         this.statsExpenses = statsExpenses;
     }
 
@@ -71,6 +72,8 @@ public void calculateStats(String command, Date d1, Date d2, Frequency frequency
      * All parameters must be present and not null.
      */
     private void basicStats(Date startDate, Date endDate) {
+        requireNonNull(startDate);
+        requireNonNull(endDate);
 
         ArrayList<ArrayList<Expense>> data = extractRelevantExpenses(startDate, endDate);
         ArrayList<ArrayList<Object>> tableData = generateSummary(data);
@@ -97,6 +100,10 @@ private void basicStats(Date startDate, Date endDate) {
      * All parameters must be present and not null.
      */
     private void compareStats(Date date1, Date date2, Frequency frequency) {
+        requireNonNull(date1);
+        requireNonNull(date2);
+        requireNonNull(frequency);
+
         Date startDate1 = date1;
         Date startDate2 = date2;
 
@@ -161,6 +168,9 @@ private void compareStats(Date date1, Date date2, Frequency frequency) {
      * All parameters must be present and not null.
      */
     private void trendStats(Date startDate, Date endDate, Frequency frequency) {
+        requireNonNull(startDate);
+        requireNonNull(endDate);
+        requireNonNull(frequency);
 
         ArrayList<ArrayList<ArrayList<Expense>>> data = new ArrayList<>();
         Date dateTracker = startDate;
@@ -352,6 +362,8 @@ private ArrayList<ArrayList<Expense>> extractRelevantExpenses(Date startDate, Da
      * Converts String Category into Int Category
      */
     protected int convertCategoryToInteger(String categoryInString) {
+        requireNonNull(categoryInString);
+
         switch (categoryInString) {
         case "FOOD":
             return FOOD;
@@ -382,6 +394,7 @@ protected int convertCategoryToInteger(String categoryInString) {
      * Converts Int Category into String Category
      */
     protected String convertIntegerCategoryToString(int categoryInInteger) {
+        requireNonNull(categoryInInteger);
         switch (categoryInInteger) {
         case FOOD:
             return "FOOD";
@@ -412,6 +425,9 @@ protected String convertIntegerCategoryToString(int categoryInInteger) {
      * Builds table for display
      */
     private String htmlTableBuilder(ArrayList<String> header, ArrayList<ArrayList<String>> data) {
+        requireNonNull(header);
+        requireNonNull(data);
+
         String table;
         table = "<table style=\"width:100%\">\n";
 

src/test/java/seedu/address/model/statistics/StatisticsTest.java

@@ -0,0 +1,78 @@
+package seedu.address.model.statistics;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static seedu.address.testutil.TypicalExpenses.DUCK_RICE;
+
+import javafx.collections.transformation.FilteredList;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import seedu.address.model.attributes.Date;
+import seedu.address.model.attributes.Frequency;
+import seedu.address.model.expense.Expense;
+import seedu.address.model.expense.ExpenseList;
+import seedu.address.testutil.Assert;
+
+public class StatisticsTest {
+
+    private ExpenseList expenseList = new ExpenseList();
+    FilteredList<Expense> statsExpenses = new FilteredList<Expense>(
+            expenseList.asUnmodifiableObservableList());
+
+    @Rule
+    public ExpectedException thrown = ExpectedException.none();
+
+    @Test
+    public void constructor_null_throwsNullPointerException() {
+        Assert.assertThrows(NullPointerException.class, () ->
+                new Statistics(null));
+    }
+
+    @Test
+    public void basicStats_parameters_null_throwsNullPointerException() {
+        Statistics stats = new Statistics(statsExpenses);
+        Date date = new Date("01-01-2019");
+        //startDate cannot be null
+        Assert.assertThrows(NullPointerException.class, () ->
+                stats.calculateStats("stats", null, date, null));
+        //endDate cannot be null
+        Assert.assertThrows(NullPointerException.class, () ->
+                stats.calculateStats("stats", date, null, null));
+    }
+
+    @Test
+    public void compareStats_parameters_null_throwsNullPointerException() {
+        Statistics stats = new Statistics(statsExpenses);
+        Date date = new Date("01-01-2019");
+        Frequency frequency = new Frequency("M");
+        //date1 cannot be null
+        Assert.assertThrows(NullPointerException.class, () ->
+                stats.calculateStats("compare", null, date  , frequency));
+        //date2 cannot be null
+        Assert.assertThrows(NullPointerException.class, () ->
+                stats.calculateStats("compare", date, null, frequency));
+        //date2 cannot be null
+        Assert.assertThrows(NullPointerException.class, () ->
+                stats.calculateStats("compare", date, date, null));
+    }
+
+    @Test
+    public void trendStats_parameters_null_throwsNullPointerException() {
+        Statistics stats = new Statistics(statsExpenses);
+        Date date = new Date("01-01-2019");
+        Frequency frequency = new Frequency("M");
+        //date1 cannot be null
+        Assert.assertThrows(NullPointerException.class, () ->
+                stats.calculateStats("trend", null, date  , frequency));
+        //date2 cannot be null
+        Assert.assertThrows(NullPointerException.class, () ->
+                stats.calculateStats("trend", date, null, frequency));
+        //date2 cannot be null
+        Assert.assertThrows(NullPointerException.class, () ->
+                stats.calculateStats("trend", date, date, null));
+    }
+
+
+}