diff --git a/tests/posix/common/src/stropts.c b/tests/posix/common/src/stropts.c
index a1c550062d6..9dcf899ca94 100644
--- a/tests/posix/common/src/stropts.c
+++ b/tests/posix/common/src/stropts.c
@@ -59,4 +59,13 @@ ZTEST(stropts, test_getpmsg)
 	zassert_equal(errno, ENOSYS, "Expected errno ENOSYS, got %d", errno);
 }
 
+ZTEST(stropts, test_isastream)
+{
+	int fd = -1;
+	int ret = isastream(fd);
+
+	zassert_equal(ret, -1, "Expected return value -1, got %d", ret);
+	zassert_equal(errno, ENOSYS, "Expected errno ENOSYS, got %d", errno);
+}
+
 ZTEST_SUITE(stropts, NULL, NULL, NULL, NULL, NULL);
diff --git a/tests/posix/headers/src/stropts_h.c b/tests/posix/headers/src/stropts_h.c
index 2cc5c7a859e..fe928e04c2c 100644
--- a/tests/posix/headers/src/stropts_h.c
+++ b/tests/posix/headers/src/stropts_h.c
@@ -23,6 +23,7 @@ ZTEST(posix_headers, test_stropts_h)
 	zassert_not_null((void *)fattach, "fattach is null");
 	zassert_not_null((void *)getmsg, "getmsg is null");
 	zassert_not_null((void *)getpmsg, "getpmsg is null");
+	zassert_not_null((void *)isastream, "isastream is null");
 
 	zassert_true(sizeof(((struct strbuf *)0)->maxlen) > 0, "maxlen size is 0");
 	zassert_true(sizeof(((struct strbuf *)0)->len) > 0, "len size is 0");