Desire form

lib/verb.rb

@@ -92,6 +92,10 @@ class Verb
   def short_form_past_negative
     short_form_present_negative.all_but_last_character + "かった"
   end
+
+  def desire
+    stem + "たい"
+  end
 end
 
 class IchidanVerb < Verb

test/test_verb.rb

@@ -127,4 +127,15 @@ class TestVerb < Minitest::Test
     assert_equal "勉強しなかった", @benkyousuru.short_form_past_negative.kanji
     assert_equal "べんきょうしなかった", @benkyousuru.short_form_past_negative.kana
   end
+
+  def test_desire
+    assert_equal "見たい", @miru.desire.kanji
+    assert_equal "みたい", @miru.desire.kana
+    assert_equal "飲みたい", @nomu.desire.kanji
+    assert_equal "のみたい", @nomu.desire.kana
+    assert_equal "したい", @suru.desire.kanji
+    assert_equal "したい", @suru.desire.kana
+    assert_equal "勉強したい", @benkyousuru.desire.kanji
+    assert_equal "べんきょうしたい", @benkyousuru.desire.kana
+  end
 end