add nf-test test instructions to contributing and PR template

nf_core/pipeline-template/.github/CONTRIBUTING.md

@@ -31,8 +31,11 @@ If you're not used to this workflow with git, you can start with some [docs from
 
 ## Tests
 
-You can optionally test your changes by running the pipeline locally. Then it is recommended to use the `debug` profile to
-receive warnings about process selectors and other debug info. Example: `nextflow run . -profile debug,test,docker --outdir <OUTDIR>`.
+You have the option to test your changes locally by running the pipeline. For receiving warnings about process selectors and other `debug` information, it is recommended to use the debug profile. Execute all the tests with the following command:
+
+```
+nf-test test --profile debug,test,docker --verbose
+```
 
 When you create a pull request with changes, [GitHub Actions](https://github.com/features/actions) will run automatic tests.
 Typically, pull-requests are only fully reviewed when these tests are passing, though of course we can help out before then.

nf_core/pipeline-template/.github/PULL_REQUEST_TEMPLATE.md

@@ -20,7 +20,7 @@ Learn more about contributing: [CONTRIBUTING.md](https://github.com/{{ name }}/t
 - [ ] If necessary, also make a PR on the {{ name }} _branch_ on the [nf-core/test-datasets](https://github.com/nf-core/test-datasets) repository.
       {%- endif %}
 - [ ] Make sure your code lints (`nf-core lint`).
-- [ ] Ensure the test suite passes (`nextflow run . -profile test,docker --outdir <OUTDIR>`).
+- [ ] Ensure the test suite passes (`nf-test test main.nf.test -profile test,docker`).
 - [ ] Check for unexpected warnings in debug mode (`nextflow run . -profile debug,test,docker --outdir <OUTDIR>`).
 - [ ] Usage Documentation in `docs/usage.md` is updated.
 - [ ] Output Documentation in `docs/output.md` is updated.