public static String getUnresolvedSchemaName(final Schema schema) {
    if (!isUnresolvedSchema(schema)) {
      throw new IllegalArgumentException("Not a unresolved schema: " + schema);
    }
    return schema.getProp(UR_SCHEMA_ATTR);
  }
@Test(expected = IllegalArgumentException.class)
  public void testIsUnresolvedSchemaError2() {
    // No "UnresolvedSchema" property
    Schema s = SchemaBuilder.record("R").prop("org.apache.avro.idl.unresolved.name", "x").fields().endRecord();
    SchemaResolver.getUnresolvedSchemaName(s);
  }