diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 0.2.1
+
+- Add size, valid, validate, and debugPrint for NonEmpty
+  [#26](https://github.com/futurice/haskell-tdigest/pull/26)
+
 ## 0.2
 
 - Add `Data.TDigest.Vector` module.
diff --git a/src/Data/TDigest/Tree/NonEmpty.hs b/src/Data/TDigest/Tree/NonEmpty.hs
--- a/src/Data/TDigest/Tree/NonEmpty.hs
+++ b/src/Data/TDigest/Tree/NonEmpty.hs
@@ -49,6 +49,12 @@
     -- ** CDF
     cdf,
     icdf,
+
+    -- * Debug
+    size,
+    valid,
+    validate,
+    debugPrint,
     ) where
 
 import Prelude ()
@@ -154,6 +160,18 @@
 
 tdigest :: (Foldable1 f, KnownNat comp) => f Double -> TDigest comp
 tdigest = TDigest . T.tdigest
+
+size :: TDigest comp -> Int
+size = T.size . unEmpty
+
+valid :: TDigest comp -> Bool
+valid = T.valid . unEmpty
+
+validate :: TDigest comp -> Either String (TDigest comp)
+validate = fmap TDigest . T.validate . unEmpty
+
+debugPrint :: TDigest comp -> IO ()
+debugPrint = T.debugPrint . unEmpty
 
 -- $setup
 -- >>> :set -XDataKinds
diff --git a/tdigest.cabal b/tdigest.cabal
--- a/tdigest.cabal
+++ b/tdigest.cabal
@@ -1,6 +1,6 @@
 cabal-version:  >= 1.10
 name:           tdigest
-version:        0.2
+version:        0.2.1
 
 synopsis:       On-line accumulation of rank-based statistics
 description:    A new data structure for accurate on-line accumulation of rank-based statistics such as quantiles and trimmed means.
@@ -52,7 +52,7 @@
   build-depends:
       base-compat         >=0.10.1   && <0.11
     , reducers            >=3.12.2   && <3.13
-    , semigroupoids       >=5.2.2    && <5.3
+    , semigroupoids       >=5.2.2    && <5.4
     , vector              >=0.12.0.1 && <0.13
     , vector-algorithms   >=0.7.0.1  && <0.8
 
@@ -96,7 +96,7 @@
     semigroups,
     vector,
     vector-algorithms,
-    tasty            >=0.11.0.4 && <1.1,
+    tasty            >=0.11.0.4 && <1.2,
     tasty-quickcheck >=0.8.4    && <0.11
 
 test-suite doctests
@@ -108,4 +108,4 @@
 
   build-depends:
     base,
-    doctest        >=0.11.1 && <0.16
+    doctest        >=0.11.1 && <0.17