Use of test/resource files to compare unit test output = code smell?

Is it a code smell to use a generated file, like a spreadsheet or XML file, as a source for comparison in Unit tests?

Say that we had to write a lot of classes that produce various XML files for processing later. The unit tests would be a large number of repetitive assertions that foo.getExpectedValue() = expectedValue. Instead of doing this, the developer chooses to use the code they are supposed to be testing to generate the XML, then copy that into test/resources for all future tests load into memory as an object and to run their assertions against?