meson/docs/markdown/snippets/test_setup_is_default.md

New keyword argument is_default to add_test_setup()

The keyword argument is_default may be used to set whether the test setup should be used by default whenever meson test is run without the --setup option.

add_test_setup('default', is_default: true, env: 'G_SLICE=debug-blocks')
add_test_setup('valgrind', env: 'G_SLICE=always-malloc', ...)
test('mytest', exe)

For the example above, running meson test and meson test --setup=default is now equivalent.