@Test
public void testCreateExpression() {

    Expression expression = Expression.createExpression("hello", "there");
    assertEquals("hello", expression.getExpression());
    assertEquals("there", expression.getLanguage());
    expression = Expression.createExpression("hello", null);
    assertEquals("hello", expression.getExpression());
    assertNull(expression.getLanguage());
    expression = Expression.createExpression(null, "there");
    assertNull(expression);
}