diff --git a/test/bigdecimal/helper.rb b/test/bigdecimal/helper.rb
index 46721fb9..0747855b 100644
--- a/test/bigdecimal/helper.rb
+++ b/test/bigdecimal/helper.rb
@@ -1,9 +1,23 @@
 # frozen_string_literal: false
 require "test/unit"
 require "bigdecimal"
-require 'rbconfig/sizeof'
+require "rbconfig/sizeof"
 
 module TestBigDecimalBase
+  ROUNDING_MODE_MAP = [
+    [ BigDecimal::ROUND_UP,        :up],
+    [ BigDecimal::ROUND_DOWN,      :down],
+    [ BigDecimal::ROUND_DOWN,      :truncate],
+    [ BigDecimal::ROUND_HALF_UP,   :half_up],
+    [ BigDecimal::ROUND_HALF_UP,   :default],
+    [ BigDecimal::ROUND_HALF_DOWN, :half_down],
+    [ BigDecimal::ROUND_HALF_EVEN, :half_even],
+    [ BigDecimal::ROUND_HALF_EVEN, :banker],
+    [ BigDecimal::ROUND_CEILING,   :ceiling],
+    [ BigDecimal::ROUND_CEILING,   :ceil],
+    [ BigDecimal::ROUND_FLOOR,     :floor],
+  ]
+
   if RbConfig::SIZEOF.key?("int64_t")
     SIZEOF_DECDIG = RbConfig::SIZEOF["int32_t"]
     BASE = 1_000_000_000
@@ -14,6 +28,26 @@ module TestBigDecimalBase
     BASE_FIG = 4
   end
 
+  if defined? RbConfig::LIMITS
+    LIMITS = RbConfig::LIMITS
+  else
+    require "fiddle"
+    LONG_MAX = (1 << (Fiddle::SIZEOF_LONG*8 - 1)) - 1
+    LONG_MIN = [LONG_MAX + 1].pack("L!").unpack("l!")[0]
+    LLONG_MAX = (1 << (Fiddle::SIZEOF_LONG_LONG*8 - 1)) - 1
+    LLONG_MIN = [LLONG_MAX + 1].pack("Q!").unpack("q!")[0]
+    ULLONG_MAX = (1 << Fiddle::SIZEOF_LONG_LONG*8) - 1
+    LIMITS = {
+      "LLONG_MIN" => LLONG_MIN,
+      "ULLONG_MAX" => ULLONG_MAX,
+      "FIXNUM_MIN" => LONG_MIN / 2,
+      "FIXNUM_MAX" => LONG_MAX / 2,
+      "INT64_MIN"  => -9223372036854775808,
+      "INT64_MAX"  => 9223372036854775807,
+      "UINT64_MAX" => 18446744073709551615,
+    }.freeze
+  end
+
   def setup
     @mode = BigDecimal.mode(BigDecimal::EXCEPTION_ALL)
     BigDecimal.mode(BigDecimal::EXCEPTION_ALL, true)
diff --git a/test/bigdecimal/test_bigdecimal.rb b/test/bigdecimal/test_bigdecimal.rb
index 0cd85249..0f3b0cc2 100644
--- a/test/bigdecimal/test_bigdecimal.rb
+++ b/test/bigdecimal/test_bigdecimal.rb
@@ -5,40 +5,6 @@
 class TestBigDecimal < Test::Unit::TestCase
   include TestBigDecimalBase
 
-  if defined? RbConfig::LIMITS
-    LIMITS = RbConfig::LIMITS
-  else
-    require 'fiddle'
-    LONG_MAX = (1 << (Fiddle::SIZEOF_LONG*8 - 1)) - 1
-    LONG_MIN = [LONG_MAX + 1].pack("L!").unpack("l!")[0]
-    LLONG_MAX = (1 << (Fiddle::SIZEOF_LONG_LONG*8 - 1)) - 1
-    LLONG_MIN = [LLONG_MAX + 1].pack("Q!").unpack("q!")[0]
-    ULLONG_MAX = (1 << Fiddle::SIZEOF_LONG_LONG*8) - 1
-    LIMITS = {
-      "LLONG_MIN" => LLONG_MIN,
-      "ULLONG_MAX" => ULLONG_MAX,
-      "FIXNUM_MIN" => LONG_MIN / 2,
-      "FIXNUM_MAX" => LONG_MAX / 2,
-      "INT64_MIN"  => -9223372036854775808,
-      "INT64_MAX"  => 9223372036854775807,
-      "UINT64_MAX" => 18446744073709551615,
-    }.freeze
-  end
-
-  ROUNDING_MODE_MAP = [
-    [ BigDecimal::ROUND_UP,        :up],
-    [ BigDecimal::ROUND_DOWN,      :down],
-    [ BigDecimal::ROUND_DOWN,      :truncate],
-    [ BigDecimal::ROUND_HALF_UP,   :half_up],
-    [ BigDecimal::ROUND_HALF_UP,   :default],
-    [ BigDecimal::ROUND_HALF_DOWN, :half_down],
-    [ BigDecimal::ROUND_HALF_EVEN, :half_even],
-    [ BigDecimal::ROUND_HALF_EVEN, :banker],
-    [ BigDecimal::ROUND_CEILING,   :ceiling],
-    [ BigDecimal::ROUND_CEILING,   :ceil],
-    [ BigDecimal::ROUND_FLOOR,     :floor],
-  ]
-
   def assert_nan(x)
     assert(x.nan?, "Expected #{x.inspect} to be NaN")
   end