test: shuffle tests

luatest has an option --shuffle that allows to randomise the order of
tests. This can be useful to detect a test that passes just because it
happens to run after an unrelated test that leaves the system in a
favourable state. Patch enable tests shuffling with predefined random
seed specified by $RANDOM. Seed is useful for reproducing a problems
related to the specific test order.

Author: ligurio

Makefile

@@ -7,7 +7,7 @@ LUACOV_REPORT := $(PROJECT_DIR)/luacov.report.out
 LUACOV_STATS := $(PROJECT_DIR)/luacov.stats.out
 
 SHELL := $(shell which bash) # Required for brace expansion used in a clean target.
-SEED := $(shell /bin/bash -c "echo $$RANDOM")
+SEED ?= $(shell /bin/bash -c "echo $$RANDOM")
 
 CLEANUP_FILES  = tarantool.log
 CLEANUP_FILES += *.index
@@ -33,7 +33,7 @@ luacheck:
 
 .PHONY: test
 test:
-	luatest -v --coverage --shuffle all:${SEED} --seed ${SEED}
+	luatest -v --coverage --shuffle all:${SEED}
 	rm -rf ${CLEANUP_FILES}
 	INDEX_TYPE='TREE' SPACE_TYPE='vinyl' ./test.lua
 	rm -rf ${CLEANUP_FILES}