Allow to choose luatest cases to run

[ylobankov]

Closes #339

[Totktonada]

Ah, no, just one problem :)

python -m flake8 .py lib/.py lib/options.py:328:76: W291 trailing whitespace

[ylobankov]

Ah, no, just one problem :)

python -m flake8 .py lib/.py lib/options.py:328:76: W291 trailing whitespace

Fixed.

[Totktonada]

I found a problem. Please, try the following test on test-run's master:

./test/test-run.py --force engine-luatest/gh_6436_field_constraint_test.lua

Tracked down to the unexpected shuffle value:

diff --git a/luatest/runner.lua b/luatest/runner.lua
index e141869..0b33423 100644
--- a/luatest/runner.lua
+++ b/luatest/runner.lua
@@ -461,6 +461,8 @@ function Runner.mt:find_tests()

     local result = {}

+    print('SSSSH: ' .. tostring(self.shuffle))
+
     for _, name in ipairs(self.test_names or self:all_test_names()) do
         local group = self.groups[name]
         if group then

[001] SSSSH: group

After returning back <...>, '--shuffle', 'none'] into the Popen call it is none:

[001] SSSSH: none

I don't investigate it further.

[Totktonada]

Filed https://github.com/tarantool/luatest/issues/306. It was fixed in https://github.com/tarantool/luatest/pull/307 against luatest itself. The change will go to test-run in https://github.com/tarantool/test-run/pull/390.