TST: Add a test for gh-23598

2 files changed, 13 insertions, 1 deletions

diff --git a/numpy/f2py/tests/src/crackfortran/gh23598.f90 b/numpy/f2py/tests/src/crackfortran/gh23598.f90
new file mode 100644
index 000000000..e0dffb5ef
--- /dev/null
+++ b/numpy/f2py/tests/src/crackfortran/gh23598.f90
@@ -0,0 +1,4 @@
+integer function intproduct(a, b) result(res)
+  integer, intent(in) :: a, b
+  res = a*b
+end function
diff --git a/numpy/f2py/tests/test_crackfortran.py b/numpy/f2py/tests/test_crackfortran.py
index 23965087d..886fc596e 100644
--- a/numpy/f2py/tests/test_crackfortran.py
+++ b/numpy/f2py/tests/test_crackfortran.py
@@ -322,4 +322,12 @@ class TestNameArgsPatternBacktracking:
         # we accept that maybe the median might double once, due to
         # the CPU scheduler acting weird or whatever. More than that
         # seems suspicious.
-        assert times_median_doubled < 2
\ No newline at end of file
+        assert times_median_doubled < 2
+
+
+class TestFunctionReturn(util.F2PyTest):
+    sources = [util.getpath("tests", "src", "crackfortran", "gh23598.f90")]
+
+    def test_function_rettype(self):
+        # gh-23598
+        assert self.module.intproduct(3, 4) == 12