static String getUnresolvedSchemaName(final Schema schema) {
    if (!isUnresolvedSchema(schema)) {
      throw new IllegalArgumentException("Not a unresolved schema: " + schema);
    }
    return schema.getProp(UR_SCHEMA_ATTR);
  }
@Test
  void isUnresolvedSchemaError1() {
    assertThrows(IllegalArgumentException.class, () -> {
      // No "org.apache.avro.compiler.idl.unresolved.name" property
      Schema s = SchemaBuilder.record("R").fields().endRecord();
      SchemaResolver.getUnresolvedSchemaName(s);
    });
  }