Usage:
  v [-stats] test FILE|DIRECTORY[...] [-run-only GPATTERN1[,...]]
    Runs test functions in the given FILEs and DIRECTORYs.

    If '-stats' is given, more statistics about the tests are printed along
    with a report of passes/failures

    If you give `-run-only GPATTERN`, then *only* test functions, that do
    match by name the given glob pattern `GPATTERN` will run. You can separate
    multiple glob patterns with `,`.
    If a _test.v file lacks matching functions for all of the glob patterns, it
    will be ignored completely, so you can do in effect:
        `v test . -run-only test_your_fn_name`
    ... and V will run only that test function, no matter how many _test.v
    files you have, and how many other test_ functions exist in them.
    NB: glob patterns support `*` which matches anything, and `?`, that
    matches any single character. They are *NOT* regular expressions however.

NB 1: very frequently, when you work on a module you can cd into its folder,
and then you can perform:
      v test .
... to run all the module's '_test.v' files.

NB 2: V builtin testing requires you to name your files with a _test.v
suffix, and to name your test functions with test_ prefix. Each function,
that starts with 'fn test_', and that is in a '_test.v' file will be called
automatically by the test framework.

NB 3: You can use `assert condition` inside each 'test_' function. If the
asserted condition fails, then v will record that, and produce a more detailed
error message, about where the failure was.

NB 4: Alternative test runners (for IDE integrations):
You can use several alternative test result formats, using `-test-runner name`,
or by setting VTEST_RUNNER (the command line option has higher priority).

The names of the available test runners are:
    `simple` Fastest, does not import additional modules, does no processing.
    `tap`    Format the output as required by the Test Anything Protocol (TAP).
    `normal` Supports color output, nicest/most human readable, the default.

You can also implement your own custom test runner, by providing the path to
your .v file, that implements it to this option. For example, see:
vlib/v/preludes/test_runner_tap.v .

NB 5: Filtering only specific _test.v files by name:
You can set the environment variable `VTEST_ONLY` to a list of strings, that
will have to be contained in the paths of the _test.v files.

Example:
    `VTEST_ONLY=complex,stats v test . -run-only *sin*`

This will find all _test.v files that have either `complex` or `stats`
in their path, then for these test files, V test will find all that contain
`test_` functions that glob match `*sin*`, and run only them, so you
should see something like this:
```
 OK    [1/2]   164.671 ms vlib/math/stats/stats_test.v
 OK    [2/2]   184.842 ms vlib/math/complex/complex_test.v
------------------------------------------------------------------------------------------
 Summary for all V _test.v files: 2 passed, 2 total. Runtime: 185 ms, on 2 parallel jobs.
```
