Theory that fails may return a more explanatory message

[olivierdemeijer]

Actually, when a @theory fails, it throws a ParameterizedAssertionError that gives theory's method name and used argument(s) : ok, we know what failed.
But to know why it failed, one have to go deep down the stack trace (20+ lines of call stack) to retrieve the root cause of the failure, obviously the message returned by the failing assertion.

Example :
There was 1 failure:
1) returnFizzWhenValueIsAMultipleOfThree(FizzBuzzTest)
org.junit.experimental.theories.internal.ParameterizedAssertionError: returnFizzWhenValueIsAMultipleOfThree(three)
at
* Starting from here, information is irrelevant when trying to understand why a theory failed*
org.junit.experimental.theories.Theories$TheoryAnchor.reportParameterizedError(Theories.java:183)
<26 lines of call stack cut>
...
at org.junit.runner.JUnitCore.main(JUnitCore.java:38)

* Caused by: org.junit.ComparisonFailure: expected:<[fizz]> but was:<[a string]>* At least !!
at org.junit.Assert.assertEquals(Assert.java:124)
...

I would suggest to add assertion failure message as a part of the ParameterizedAssertionError, in order to have all relevant and needed information on the very first line of the stack trace.

+1 for printing assertion failure message. It would make live much easier.

Found workaround. Use ErrorCollector instead of assert. Snippet here https://gist.github.com/ludvicekj/9ca6a926948e14631f93

[marcphilipp]

We could do something like Sping's NestedRuntimeException, i.e. append the message of the cause of the ParameterizedAssertionError.

That would look like this:

returnFizzWhenValueIsAMultipleOfThree(FizzBuzzTest)
org.junit.experimental.theories.internal.ParameterizedAssertionError: returnFizzWhenValueIsAMultipleOfThree(three); caused by org.junit.ComparisonFailure: expected:<[fizz]> but was:<[a string]>
at org.junit.experimental.theories.Theories$TheoryAnchor.reportParameterizedError(Theories.java:183)
...
at org.junit.runner.JUnitCore.main(JUnitCore.java:38)
Caused by: org.junit.ComparisonFailure: expected:<[fizz]> but was:<[a string]>
at org.junit.Assert.assertEquals(Assert.java:124)
...

@olivierdemeijer @ludvicekj Would that help?

[giorgiosironi]

👍 on a comprehensive error message. Should I open a PR for that?