diff --git a/tests/README b/tests/README
index 971c94c..23ca241 100644
--- a/tests/README
+++ b/tests/README
@@ -197,6 +197,11 @@ library for your script to use.
    context of the last argument.  <message> should state what it
    is testing.
 
+ - test_todo_custom_completion <completefunc> <message> <cmdline> <completions>
+
+   Same as above, but in addition allows to specify a custom
+   completion function.
+
  - test_tick [interval]
 
    The test harness has an internal view of time which is
diff --git a/tests/test-lib.sh b/tests/test-lib.sh
index 3e56af3..7c494d7 100644
--- a/tests/test-lib.sh
+++ b/tests/test-lib.sh
@@ -632,9 +632,11 @@ EOF
 	exit 0
 }
 
-test_todo_completion () {
-	test "$#" = 3 ||
-	error "bug in the test script: not 3 parameters to test_todo_completion"
+test_todo_custom_completion () {
+	test "$#" = 4 ||
+	error "bug in the test script: not 4 parameters to test_todo_custom_completion"
+	completeFunc=$1
+	shift
 	if ! test_skip "$@"
 	then
 		description=$1
@@ -657,7 +659,7 @@ test_todo_completion () {
 		EXPECT=("$@")
 
 		source "$TEST_DIRECTORY/../todo_completion"
-		_todo
+		$completeFunc
 		ret=$?
 		if [ "$ret" = 0 ]
 		then
@@ -684,6 +686,11 @@ $(test_cmp expect compreply)"
 	fi
 	echo >&3 ""
 }
+test_todo_completion () {
+	test "$#" = 3 ||
+	error "bug in the test script: not 3 parameters to test_todo_completion"
+	test_todo_custom_completion _todo "$@"
+}
 
 test_init_todo "$test"
 # Use -P to resolve symlinks in our working directory so that the pwd