Wrap tests in describe (#7934)

* Run `format()` in test function

* Wrap `test`s in `describe`

* Update tests_config/run_spec.js

Co-Authored-By: Georgii Dolzhykov <thorn.mailbox@gmail.com>

Co-authored-by: Georgii Dolzhykov <thorn.mailbox@gmail.com>

tests/flow/node_tests/basic_node_modules/__snapshots__/jsfmt.spec.js.snap

@@ -1,6 +1,6 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`foo.js 1`] = `
+exports[`foo.js format 1`] = `
 ====================================options=====================================
 parsers: ["flow"]
 printWidth: 80