[timtebeek]

CsvSourceToValueSource only checked the values of @CsvSource(textBlock = ...). For the value attribute it copied the strings into @ValueSource as they were, although JUnit's CSV parsing changes them. @CsvSource({"x, y", "z, w"}) void t(String s) passed "x" and "z", but after the conversion it passed "x, y" and "z, w". A probe against the JUnit on this project's test classpath showed the parser also strips single quotes, trims surrounding whitespace, rejects blank records, and splits a value with line breaks into several records. For example, the multi-line text block passed as value in the old preserveTextBlockAsValue test ran three times, with # Lower-case letters, asdf and a, not once with the whole string.

Both paths now share one check. They skip the conversion unless every value is a string literal without a comma, single quote or line break, is not blank, and has no surrounding whitespace. Non-String parameters also reject inner whitespace. Non-literal values such as constants are left alone. The old text-block test now expects no change.

The values are now read from the literals directly instead of through the Literal trait, which does not resolve Kotlin array attributes. Because of that:

• Kotlin non-String parameters are now converted (@ValueSource(ints = [1, 2, 3])) where they were left unchanged before.
• A single Kotlin value becomes strings = ["apple"] instead of strings = "apple", which does not compile.

Verified with ./gradlew test --offline --tests '*CsvSourceToValueSourceTest', which passed.

Fixes item C8 of #1211.