Fix SVDB/merge stubs

[fellen31]

PR checklist

Closes #XXX

• This comment contains a description of changes (with reason).
• If you've fixed a bug or added code that should be tested, add tests!
• If you've added a new tool - have you followed the module conventions in the contribution docs
• If necessary, include test data in your PR.
• Remove all TODO statements.
• Emit the versions.yml file.
• Follow the naming conventions.
• Follow the parameters requirements.
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• Add a resource label
• Use BioConda and BioContainers if possible to fulfil software requirements.
• Ensure that the test works with either Docker / Singularity. Conda CI tests can be quite flaky:
  • For modules:
    • nf-core modules test <MODULE> --profile docker
    • nf-core modules test <MODULE> --profile singularity
    • nf-core modules test <MODULE> --profile conda
  • For subworkflows:
    • nf-core subworkflows test <SUBWORKFLOW> --profile docker
    • nf-core subworkflows test <SUBWORKFLOW> --profile singularity
    • nf-core subworkflows test <SUBWORKFLOW> --profile conda

[Lucpen]

Just one tiny thing

[Lucpen]

why not just touch the file?

[fellen31]

1.12.4 Stub gzip files must use echo and pipe in https://nf-co.re/docs/guidelines/components/modules

Simply touching a file with the file name ending in .gz will break nf-test’s Gzip file parser, as the file is not actually gzipped and thus cannot be read.

Therefore we must make sure we generate a valid gzipped file for nf-test to accept it during tests.