Sample project demonstrating the issue:
If the tests are run all together, DirtiesContext will cause the configuration to be reloaded between each test. This will work fine for the first test that runs, but will fail for subsequent tests.
Why is this? Well, it turns out that the camel undertow component registers a type converter that causes non-bean-reference Strings to get converted to null. For some reason, this only happens on the second test within an execution.