add #dig tests

mrbgems/mruby-array-ext/test/array.rb

@@ -310,3 +310,10 @@ assert("Array#to_ary") do
   assert_equal [], [].to_ary
   assert_equal [1,2,3], [1,2,3].to_ary
 end
+
+assert("Array#dig") do
+  h = [[[1]], 0]
+  assert_equal(1, h.dig(0, 0, 0))
+  assert_nil(h.dig(2, 0))
+  assert_raise(TypeError) {h.dig(:a)}
+end

mrbgems/mruby-hash-ext/test/hash.rb

@@ -236,3 +236,9 @@ assert('Hash#>') do
   assert_false(h2 > h1)
   assert_false(h2 > h2)
 end
+
+assert("Hash#dig") do
+  h = {a:{b:{c:1}}}
+  assert_equal(1, h.dig(:a, :b, :c))
+  assert_nil(h.dig(:d))
+end

mrbgems/mruby-struct/test/struct.rb

@@ -148,3 +148,10 @@ assert('Struct#values_at') do
   assert_equal ['io', 'aki'], a.values_at(1, 0)
   assert_raise(IndexError) { a.values_at 2 }
 end
+
+assert("Struct#dig") do
+  a = Struct.new(:blue, :purple).new('aki', Struct.new(:red).new(1))
+  assert_equal 'aki', a.dig(:blue)
+  assert_equal 1, a.dig(:purple, :red)
+  assert_equal 1, a.dig(1, 0)
+end