break;
            }
        }

        return fullMessage.trim();
    }

    private String join(String message1, String message2) {
        String message = "";

        if (message1 != null && !message1.isEmpty()) {
            message = message1.trim();
        }

        if (message2 != null && !message2.isEmpty()) {
            if (message != null && !message.isEmpty()) {

        collector.add(null, "MESSAGE1", -1, -1, null);

        Exception e2 = new Exception();
        collector.add(Severity.WARNING, null, 42, 127, e2);

        assertEquals(2, collector.getProblems().size());

        Problem p1 = collector.getProblems().get(0);
        assertEquals(Severity.ERROR, p1.getSeverity());
        assertEquals("MESSAGE1", p1.getMessage());

import static org.junit.jupiter.api.Assertions.assertEquals;

class ModelBuildingExceptionTest {

    @Test
    void testMessage() {
        DefaultModelProblem pb1 =
                new DefaultModelProblem("message1", ModelProblem.Severity.ERROR, null, "source", 0, 0, "modelId", null);
        DefaultModelProblem pb2 =
                new DefaultModelProblem("message2", ModelProblem.Severity.ERROR, null, "source", 0, 0, "modelId", null);

class ProblemCollectorFactoryTest {

    @Test
    void testNewInstance() {
        ProblemCollector collector1 = ProblemCollectorFactory.newInstance(null);

        Problem problem = new DefaultProblem("MESSAGE1", null, null, -1, -1, null);
        ProblemCollector collector2 = ProblemCollectorFactory.newInstance(Collections.singletonList(problem));

        assertNotSame(collector1, collector2);