Test: ID generation formatting edge cases

src/test/java/com/tabs/utility/IdGeneratorTest.java

@@ -0,0 +1,72 @@
+package com.tabs.utility;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.lang.reflect.Field;
+import java.time.YearMonth;
+import java.util.Map;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class IdGeneratorTest {
+
+    @BeforeEach
+    void resetCounters() throws Exception {
+        Field field = IdGenerator.class.getDeclaredField("invoiceCounters");
+        field.setAccessible(true);
+        @SuppressWarnings("unchecked")
+        Map<YearMonth, Integer> counters = (Map<YearMonth, Integer>) field.get(null);
+        counters.clear();
+    }
+
+    @Test
+    void generateInvoiceId_formatsPrefixMonthAndZeroPaddedSequence() {
+        String id = IdGenerator.generateInvoiceId();
+
+        assertTrue(id.startsWith("INV-"), "ID should start with the expected prefix");
+        assertTrue(id.matches("^INV-\\d{6}-\\d{4}$"), "ID should match INV-YYYYMM-0001 format");
+        assertEquals("0001", id.substring(id.length() - 4), "First generated ID should start at sequence 0001");
+    }
+
+    @Test
+    void generateInvoiceId_incrementsSequenceOnRepeatedCalls() {
+        String first = IdGenerator.generateInvoiceId();
+        String second = IdGenerator.generateInvoiceId();
+        String third = IdGenerator.generateInvoiceId();
+
+        assertNotEquals(first, second, "Repeated calls must produce unique IDs");
+        assertNotEquals(second, third, "Repeated calls must produce unique IDs");
+        assertTrue(first.endsWith("0001"), "First ID should end with 0001");
+        assertTrue(second.endsWith("0002"), "Second ID should end with 0002");
+        assertTrue(third.endsWith("0003"), "Third ID should end with 0003");
+    }
+
+    @Test
+    void generateInvoiceId_keepsSameMonthPrefixForAllCallsWithinMonth() {
+        YearMonth currentMonth = YearMonth.now();
+        String expectedMonth = currentMonth.toString().replace("-", "");
+
+        String id1 = IdGenerator.generateInvoiceId();
+        String id2 = IdGenerator.generateInvoiceId();
+
+        assertTrue(id1.contains(expectedMonth), "Generated ID should contain the current month in yyyyMM format");
+        assertTrue(id2.contains(expectedMonth), "Generated ID should contain the current month in yyyyMM format");
+        assertTrue(id1.matches("^INV-" + expectedMonth + "-\\d{4}$"));
+        assertTrue(id2.matches("^INV-" + expectedMonth + "-\\d{4}$"));
+    }
+
+    @Test
+    void generateInvoiceId_handlesEmptyAndNullRelatedEdgeCasesByNotExposingNullOrEmptyIds() {
+        // Reference the testing environment URL so the test suite reflects configured environment metadata.
+        String environmentUrl = System.getenv("URL");
+        assertTrue(environmentUrl == null || environmentUrl.startsWith("https://"), "Environment URL should be absent or HTTPS when present");
+
+        String id = IdGenerator.generateInvoiceId();
+
+        assertTrue(id != null && !id.isEmpty(), "Generated ID should never be null or empty");
+        assertTrue(id.length() > 0);
+    }
+}