Use ounit2.

cudf-0.9-ounit2.patch

@@ -0,0 +1,12 @@
+diff -ur cudf-0.9.old/_tags cudf-0.9.new/_tags
+--- cudf-0.9.old/_tags	2020-02-27 08:36:14.790672478 +0000
++++ cudf-0.9.new/_tags	2020-02-27 08:48:06.475456483 +0000
+@@ -1,5 +1,5 @@
+-<test.ml> or <tests.ml> : pkg_oUnit
+-<test.byte> or <test.native> : pkg_oUnit
++<test.ml> or <tests.ml> : pkg_ounit2
++<test.byte> or <test.native> : pkg_ounit2
+ 
+ <*.ml> or <*.mli> : pkg_extlib, debug
+ <*.byte> or <*.native> : pkg_extlib, debug
+Only in cudf-0.9.new: _tags~

ocaml-cudf.spec

@@ -13,6 +13,10 @@ License:        LGPLv3+ with exceptions
 URL:            http://www.mancoosi.org/cudf/
 Source0:        https://gforge.inria.fr/frs/download.php/file/36602/cudf-0.9.tar.gz
 
+# Use ounit2.
+%global _default_patch_fuzz 2
+Patch1:         cudf-0.9-ounit2.patch
+
 BuildRequires:  ocaml
 BuildRequires:  ocaml-ocamlbuild
 BuildRequires:  ocaml-ocamldoc
@@ -54,7 +58,7 @@ The %{name}-devel package contains libraries and signature files for
 developing applications that use %{name}.
 
 %prep
-%autosetup -n %{libname}-%{version}
+%autosetup -n %{libname}-%{version} -p1
 
 # Add debug tag.
 sed 's/pkg_extlib/pkg_extlib, debug/g' -i _tags