test: fiber is not blocked by close/execute

Test that concurrent use of `execute` and `close` does not result
to infinite blocking.

Part of #34

Author: romanhabibov

test/mysql.test.lua

@@ -559,6 +559,14 @@ local function test_block_fiber_inf(test, pool, conn)
         return false
     end
     test:ok(is_cancelled() == false, 'fiber is not blocked (pool conn)')
+
+     -- Start the first fiber.
+    fiber.create(conn.execute, conn, 'SELECT sleep(0.01)')
+     -- Start the second fiber.
+    fiber.create(test_fiber_block_long_request, conn)
+     -- Start the third fiber.
+    fiber.create(conn.close, conn)
+    test:ok(is_cancelled() == false, 'fiber is not blocked (non pool conn)')
 end
 
 local test = tap.test('mysql connector')