test for subtraction

Author: Skorobogaty Dmitry

test/ipaddress/ipv4_test.rb

@@ -481,15 +481,16 @@ def test_method_split
   end
 
   def test_method_subnet
-    assert_raises(ArgumentError) {@network.subnet(23)}
-    assert_raises(ArgumentError) {@network.subnet(33)}
-    arr = ["172.16.10.0/26", "172.16.10.64/26", "172.16.10.128/26", 
-           "172.16.10.192/26"]
-    assert_equal arr, @network.subnet(26).map {|s| s.to_string}
-    arr = ["172.16.10.0/25", "172.16.10.128/25"]
-    assert_equal arr, @network.subnet(25).map {|s| s.to_string}
-    arr = ["172.16.10.0/24"]
-    assert_equal arr, @network.subnet(24).map {|s| s.to_string}
+  end
+
+  def test_method_subtract
+    a = IPAddress '10.0.0.0/16'
+    b = IPAddress '10.0.128.0/18'
+    c = IPAddress '192.168.0.0/16'
+
+    assert !a.subtract(b).include?(b)
+    assert b.subtract(a).empty?
+    assert_equal a, a.subtract(c).first
   end
 
   def test_method_supernet