TRUNK-6557: Add unit test for OpenmrsDateFormat 2-digit-year rejection

api/src/test/java/org/openmrs/util/OpenmrsDateFormatTest.java

@@ -0,0 +1,48 @@
+/**
+ * This Source Code Form is subject to the terms of the Mozilla Public License,
+ * v. 2.0. If a copy of the MPL was not distributed with this file, You can
+ * obtain one at http://mozilla.org/MPL/2.0/. OpenMRS is also distributed under
+ * the terms of the Healthcare Disclaimer located at http://openmrs.org/license.
+ *
+ * Copyright (C) OpenMRS Inc. OpenMRS is a registered trademark and the OpenMRS
+ * graphic logo is a trademark of OpenMRS Inc.
+ */
+package org.openmrs.util;
+
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.util.Locale;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Tests for {@link OpenmrsDateFormat}.
+ * <p>
+ * {@code OpenmrsDateFormat} is a strict-mode wrapper around {@link SimpleDateFormat} whose central
+ * reason for existing is to reject two-digit years when the pattern explicitly asks for four. Under
+ * plain {@code SimpleDateFormat}, parsing {@code "12/25/25"} against pattern {@code "MM/dd/yyyy"}
+ * silently produces the year 25 AD — the kind of clinical-timestamp bug that only surfaces months
+ * later in reports. This test pins that guarantee down so a future refactor of the regex check in
+ * {@link OpenmrsDateFormat#parse(String)} cannot weaken it without a test failing.
+ */
+public class OpenmrsDateFormatTest {
+
+	/**
+	 * @see OpenmrsDateFormat#parse(String)
+	 */
+	@Test
+	public void parse_shouldRejectTwoDigitYearWhenPatternEndsInYyyy() {
+		OpenmrsDateFormat fmt = new OpenmrsDateFormat(new SimpleDateFormat("MM/dd/yyyy", Locale.US), Locale.US);
+
+		ParseException ex = assertThrows(ParseException.class, () -> fmt.parse("12/25/25"));
+
+		// The error message is part of the contract: a downstream UI may rely on it to explain
+		// the rejection to a user typing a short-form date. Asserting the message guards both the
+		// rejection itself and the human-facing wording.
+		assertTrue(ex.getMessage().contains("year must have 4 digits"),
+		    "Expected message to call out the 4-digit-year requirement, got: " + ex.getMessage());
+	}
+}