Add tests

hapi-fhir-jpaserver-base/src/main/java/ca/uhn/fhir/jpa/util/PermutationBuilder.java

@@ -36,7 +36,7 @@ public class PermutationBuilder {
 	 *   ]
 	 * </pre>
 	 * <p>
-	 * This method may or may not return a newly created list.
+	 * This method will return a newly created list and will not modify the input lists.
 	 * </p>
 	 *
 	 * @param theInput A list of lists to calculate permutations of

hapi-fhir-jpaserver-base/src/test/java/ca/uhn/fhir/jpa/util/PermutationBuilderTest.java

@@ -7,6 +7,8 @@ import java.util.stream.IntStream;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotSame;
+import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
 class PermutationBuilderTest {
@@ -47,19 +49,35 @@ class PermutationBuilderTest {
 			List.of("A0"),
 			List.of("A1")
 		);
+		assertNotSame(input, output);
 	}
 
 	@Test
 	public void testCalculatePermutations_OneDimensonalInputOnY() {
 		List<List<String>> input = List.of(
 			List.of("A0"),
-			List.of("B0")
+			List.of("B0"),
+			List.of("C0")
 		);
 
 		List<List<String>> output = PermutationBuilder.calculatePermutations(input);
 		assertThat(output).containsExactlyInAnyOrder(
-			List.of("A0", "B0")
+			List.of("A0", "B0", "C0")
 		);
+		assertNotSame(input, output);
+	}
+
+	@Test
+	public void testCalculatePermutations_OneDimensonalInputOnXandY() {
+		List<List<String>> input = List.of(
+			List.of("A0")
+		);
+
+		List<List<String>> output = PermutationBuilder.calculatePermutations(input);
+		assertThat(output).containsExactlyInAnyOrder(
+			List.of("A0")
+		);
+		assertNotSame(input, output);
 	}
 
 	@Test