diff --git a/share/examples/tests/tests/plain/cp_test b/share/examples/tests/tests/plain/cp_test.sh
old mode 100755
new mode 100644
similarity index 100%
rename from share/examples/tests/tests/plain/cp_test
rename to share/examples/tests/tests/plain/cp_test.sh
diff --git a/share/mk/plain.test.mk b/share/mk/plain.test.mk
index b41c5856c61..2e2752db7fa 100644
--- a/share/mk/plain.test.mk
+++ b/share/mk/plain.test.mk
@@ -46,6 +46,16 @@ _TESTS+= ${PLAIN_TESTS_SH}
 .for _T in ${PLAIN_TESTS_SH}
 SCRIPTSDIR_${_T}= ${TESTSDIR}
 TEST_INTERFACE.${_T}= plain
+CLEANFILES+= ${_T} ${_T}.tmp
+# TODO(jmmv): It seems to me that this SED and SRC functionality should
+# exist in bsd.prog.mk along the support for SCRIPTS.  Move it there if
+# this proves to be useful within the tests.
+PLAIN_TESTS_SH_SED_${_T}?= # empty
+PLAIN_TESTS_SH_SRC_${_T}?= ${_T}.sh
+${_T}: ${PLAIN_TESTS_SH_SRC_${_T}}
+	cat ${.ALLSRC} | sed ${PLAIN_TESTS_SH_SED_${_T}} >${.TARGET}.tmp
+	chmod +x ${.TARGET}.tmp
+	mv ${.TARGET}.tmp ${.TARGET}
 .endfor
 .endif