An idea. You can make a type:
data TestContains = TestContains Tweet TweetSet
and the make an Arbitrary instance for it. When you do
a recursove call you have three different tweets one new tweet
and two from the sub-calls. Then you can place one of them in the
result. In the end you will have a random TweetSet with some value from it.
Here is a scratch of the implementation:
instance Arbitrary TestContains where
arbitrary = sized set'
where set' 0 = mkSingleTweet <$> (arbitrary :: Tweet)
set' n = do
t0 <- arbitrary :: Tweet
TestContains t1 ts1 <- subTweets
TestContains t2 ts2 <- subTweets
t <- oneof [t0, t1, t2]
return $ TestContains t $ TweetSet t0 ts1 ts2
subTweets = set' (n `div` 2)
2012/11/21
I have
data Tweet = Tweet { user :: String, text :: String, retweets :: Double } deriving (Show)
data TweetSet = NoTweets | SomeTweets Tweet TweetSet TweetSet
and trying to create some generators for testing, with
instance Arbitrary Tweet where arbitrary = liftM3 Tweet arbitrary arbitrary arbitrary
instance Arbitrary TweetSet where arbitrary = sized set' where set' 0 = return NoTweets set' n | n>0 = oneof[return NoTweets, liftM3 SomeTweets arbitrary subTweets subTweets] where subTweets = set' (n `div` 2)
but wondering how I would go about generating a random TweetSet that contains a known random Tweet I later have reference to and I would also assume the known Tweet to be placed randomly.
Then I could test a contains function.
Thanks
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