Add unit test for SavingsHelper to handle null posting type

fineract-core/src/test/java/org/apache/fineract/portfolio/savings/domain/SavingsHelperNPExceptionTest.java

@@ -0,0 +1,54 @@
+/**
+ * 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.
+ */
+package org.apache.fineract.portfolio.savings.domain;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.time.LocalDate;
+import java.util.ArrayList;
+import java.util.List;
+import org.apache.fineract.infrastructure.core.domain.LocalDateInterval; // Ensure this import exists
+import org.apache.fineract.portfolio.savings.SavingsPostingInterestPeriodType;
+import org.junit.jupiter.api.Test;
+
+class SavingsHelperNPExceptionTest {
+    private final SavingsHelper savingsHelper = new SavingsHelper(null);
+
+    @Test
+    void shouldNotThrowNullPointerExceptionWhenPostingPeriodTypeIsNull() {
+        LocalDate start = LocalDate.of(2025, 1, 1);
+        LocalDate end = LocalDate.of(2025, 4, 1);
+
+        // This is the NULL that was causing the crash
+        SavingsPostingInterestPeriodType nullPostingPeriodType = null;
+
+        Integer financialYearBeginningMonth = 1;
+        List<LocalDate> postInterestAsOn = new ArrayList<>();
+
+        List<LocalDateInterval> result = savingsHelper.determineInterestPostingPeriods(
+                start,
+                end,
+                nullPostingPeriodType,
+                financialYearBeginningMonth,
+                postInterestAsOn
+        );
+
+        assertTrue(result.isEmpty(), "Result should be empty when postingPeriodType is null");
+    }
+}