Set a deterministic seed for random sort index

spec/resolver_spec.rb

@@ -71,6 +71,7 @@ def run(index_class, context)
         it test_case.name do
           resolve = lambda do
             index = index_class.new(test_case.index.specs)
+            index.rng = Random.new(test_case.name.size * 5 + 7) if index.respond_to?(:rng=)
             resolver = Resolver.new(index, TestUI.new)
             resolver.resolve(test_case.requested, test_case.base)
           end

spec/spec_helper/index.rb

@@ -117,8 +117,15 @@ def sort_dependencies(*)
   end
 
   class RandomSortIndex < TestIndex
-    def sort_dependencies(dependencies, _activated, _conflicts)
-      dependencies.shuffle
+    attr_writer :rng
+    def rng
+      @rng ||= Random.new
+    end
+
+    if RUBY_VERSION >= "2.4"
+      def sort_dependencies(dependencies, _activated, _conflicts)
+        dependencies.shuffle(random: rng)
+      end
     end
   end