Ensure serialization compatibility where possible

[marcphilipp]

Not possible for org.junit.runner.Result. Potential fix for #976 (needs manual test to confirm).

[kcooney]

LGTM

Curious, how did you find which classes needed to be modified?

[marcphilipp]

I went through all classes that implement Serializable (those that declare a serialVersionUID and the two that don't) and diffed them with the r4.11 tag.

[dsaff]

Thank you, Marc!

[kcooney]

I have some ideas on how we can preserve serialization for org.junit.runner.Result. @marcphilipp do you think it's worth exploring those?

[marcphilipp]

I don't think it's that crucial for result but I'm curious to hear about your ideas.

[kcooney]

A custom writeObject method could write things in the previous format. So I was thinking of having a nested static class of Result named SerializedForm that would have fields that have the same name and ordering as the Result class had in 4.11. To serialize, we copy the data from Result to SerializedForm and manually serialize it.

The tricky part is writing a test, but the binary format is documented, so the test could populate SerializedForm and serialize it, then read the binary serialized form and change the class name to org.junit.runner.Result and write a new serialized form. Then we deserialize the data and compare the Result to the expected values.

[marcphilipp]

Do you think it's worth the effort?