Update and refine the readme

README.md

@@ -2,34 +2,86 @@
 
 [![Coverage Status](https://coveralls.io/repos/github/tarantool/test-run/badge.svg)](https://coveralls.io/github/tarantool/test-run)
 
-### Test Suite
-
-Bunch of tests, that lay down in the subfolder (recursively) with `suite.ini`
-file. `suite.ini` is basic ini-file, that consists of one section `default`,
-and a number of fields:
-
-* `core`
-* `description` - Test Suite description
-* `script` - shebang file to start tarantool with
-* disables:
-    * `disabled` - tests that must be skipped
-    * `release_disabled` - tests that must be skipped when Tarantool has been
-      builded with `Release`
-    * `valgrind_disabled` - tests that must be skipped when Valgrind is enabled
-* `lua_libs` - paths for lua files, that should be copied into the folder,
-  where server is started (delimited with the space, e.g. `lua_libs=lua/1.lua
-  lua/2.lua`)
-* `long_run` - mark tests as long, enabled only with `--long` option (delimited
-  with the space, e.g. `long_run=t1.test.lua t2.test.lua`)
-* `config` - test configuration file name
-
-Field `core` must be one of:
-
-* `tarantool` - Test-Suite for Functional Testing
-* `app` - Another functional Test-Suite
-* `unittest` - Unit-Testing Test Suite
-
-### Test
+## Test suite configuration
+
+Test suite is a bunch of tests located in a subdirectory (recursively) with a `suite.ini`
+file. The `suite.ini` is a basic ini-file with one section `[default]`.
+
+```ini
+[default]
+core = luatest
+description = Example test suite using luatest
+...
+```
+
+All list values in `suite.ini` are delimited by spaces.
+
+A `suite.ini` file can have the following fields.
+
+### General configuration
+
+* `core` — major testing dependency or method
+  Should have one of the following values:
+
+  * `tarantool` — test suite used for functional testing
+  * `app` — TAP-tests, another functional test suite
+  * `unittest` — unit testing test suite
+  * `luatest` — test suite using luatest library
+
+* `description` — test suite description
+* `script` (optional) — shebang file to start tarantool with
+
+### Skipping tests
+A number of fields are used to disable (skip) certain tests:
+
+* `disabled` — list of tests that should be skipped
+* `release_disabled` — list of tests that should be skipped when Tarantool is
+    built with `Release`
+* `valgrind_disabled` — list of tests that should be skipped when Valgrind is enabled
+* `long_run` — mark tests as long, such tests will run only with `--long` option.
+
+  ```ini
+  long_run = long_run=t1.test.lua t2.test.lua
+  ```
+
+### Other parameters
+
+* `lua_libs` — paths for lua files, that should be copied into the folder,
+  where server is started. For example:
+
+  ```ini
+  lua_libs = lua/require_mod.lua lua/serializer_test.lua lua/process_timeout.lua
+  ```
+
+* `config` — name of a test configuration file
+* `show_reproduce_content` (optional, `True` by default) — ?
+* `is_parallel` (optional, `False` by default) — whether the tests in the suite can run in parallel
+
+* `use_unix_sockets_iproto` (optional, `False` by default) — use hard-coded unix sockets
+* `use_unix_sockets_iproto` (optional, `False` by default) — use hard-coded unix sockets for iproto.
+  This parameter is specific to `core = app`.
+
+### Fragile tests
+
+Tests which fail sometimes due to external reasons can be marked as fragile (flaky).
+Test-run will retry each test if it fails.
+It's recommended to add a list of related issues in the
+[tarantool/tarantool](https://github.com/tarantool/tarantool) repository.
+
+```ini
+fragile = {
+    "retries": 10,
+    "tests": {
+        "tarantoolctl.test.lua": {
+            "issues": [ "gh-5059", "gh-5346" ],
+        },
+        {...},
+        {...},
+    }
+}
+```
+
+## Test
 
 Each test consists of files `*.test(.lua|.sql|.py)?`, `*.result`, and may have
 skip condition file `*.skipcond`.  On first run (without `.result`) `.result`