bashunit --output junit produces invalid XML (a blank line precedes the declaration)

[Chemaclass]

Problem

The plain documented command produces XML that no parser accepts:

$ bashunit --output junit tests/ > report.xml
$ xmllint --noout report.xml
report.xml:2: parser error : XML declaration allowed only at the start of the document

The first byte of the document is a newline. Parallel output is fine, and parallel is not the default (_BASHUNIT_DEFAULT_PARALLEL_RUN="false"), so the default invocation is the broken one.

Cause

bashunit::runner::run_tear_down_after_script prints a blank line between a file's tests and the next when the file has no tear_down_after_script. It is guarded against --simple, --failures-only, --no-progress and --parallel — but not against a machine --output. The document is written at the end of the run, so the blank line lands in front of it.

Reproduced by mode:

run	first bytes	xmllint
--no-parallel --output junit	\n<?xml	parser error
--parallel --output junit	<?xml	OK

--output json gains the same leading blank line. It went unnoticed because JSON tolerates leading whitespace, so jq accepts it and the existing test — which only checks that it parses — stayed green.

Why the existing guard missed it

test_output_junit_starts_with_the_xml_declaration_under_parallel exists for exactly this hazard but pins only the parallel path, which is the one that was already correct.

Fix

Suppress the blank line for json and junit. Name those two formats rather than using is_machine_output_enabled, which also covers tap: TAP streams line by line, a blank line between files is valid there, and its snapshots record it — using the broader predicate changes two TAP snapshots for no reason.

[Chemaclass]

Done in #1244 (merged).