gnu: Add ghc-haddock-test.

* gnu/packages/haskell.scm (ghc-haddock-test): New variable.

gnu/packages/haskell.scm

@@ -694,6 +694,28 @@ the ‘haddock’ package.")
 documentation-generation tool for Haskell libraries.")
     (license license:bsd-3)))
 
+(define-public ghc-haddock-test
+  (package
+    (name "ghc-haddock-test")
+    (version "0.0.1")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (string-append "https://hackage.haskell.org/package/"
+                           "haddock-test/haddock-test-"
+                           version ".tar.gz"))
+       (sha256
+        (base32
+         "1ax8fnfrwx66csj952f3virxzapipan9da7z5l1zc12nqkifbs7w"))))
+    (build-system haskell-build-system)
+    (inputs
+     `(("ghc-xml" ,ghc-xml)
+       ("ghc-syb" ,ghc-syb)))
+    (home-page "http://www.haskell.org/haddock/")
+    (synopsis "Test utilities for Haddock")
+    (description "This package provides test utilities for Haddock.")
+    (license license:bsd-3)))
+
 (define-public ghc-haddock
   (package
     (name "ghc-haddock")