test: Add the beginnings of some string tests

There are quite a few string functions in U-Boot with no tests. Make a
start by adding a test for strtoul().

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/str_ut.c b/test/str_ut.c
new file mode 100644
index 0000000..fab8de5
--- /dev/null
+++ b/test/str_ut.c
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2020 Google LLC
+ */
+
+#include <common.h>
+#include <vsprintf.h>
+#include <test/suites.h>
+#include <test/test.h>
+#include <test/ut.h>
+
+/* This is large enough for any of the test strings */
+#define TEST_STR_SIZE	200
+
+static const char str1[] = "I'm sorry I'm late.";
+static const char str2[] = "1099abNo, don't bother apologising.";
+static const char str3[] = "0xbI'm sorry you're alive.";
+
+/* Declare a new str test */
+#define STR_TEST(_name, _flags)		UNIT_TEST(_name, _flags, str_test)
+
+static int run_strtoul(struct unit_test_state *uts, const char *str, int base,
+		       ulong expect_val, int expect_endp_offset)
+{
+	char *endp;
+	ulong val;
+
+	val = simple_strtoul(str, &endp, base);
+	ut_asserteq(expect_val, val);
+	ut_asserteq(expect_endp_offset, endp - str);
+
+	return 0;
+}
+
+static int str_simple_strtoul(struct unit_test_state *uts)
+{
+	/* Base 10 and base 16 */
+	ut_assertok(run_strtoul(uts, str2, 10, 1099, 4));
+	ut_assertok(run_strtoul(uts, str2, 16, 0x1099ab, 6));
+
+	/* Invalid string */
+	ut_assertok(run_strtoul(uts, str1, 10, 0, 0));
+
+	/* Base 0 */
+	ut_assertok(run_strtoul(uts, str1, 0, 0, 0));
+	ut_assertok(run_strtoul(uts, str2, 0, 1099, 4));
+	ut_assertok(run_strtoul(uts, str3, 0, 0xb, 3));
+
+	/* Base 2 */
+	ut_assertok(run_strtoul(uts, str1, 2, 0, 0));
+	ut_assertok(run_strtoul(uts, str2, 2, 2, 2));
+
+	/* Check endp being NULL */
+	ut_asserteq(1099, simple_strtoul(str2, NULL, 0));
+
+	return 0;
+}
+STR_TEST(str_simple_strtoul, 0);
+
+int do_ut_str(cmd_tbl_t *cmdtp, int flag, int argc, char *const argv[])
+{
+	struct unit_test *tests = ll_entry_start(struct unit_test,
+						 str_test);
+	const int n_ents = ll_entry_count(struct unit_test, str_test);
+
+	return cmd_ut_category("str", "str_", tests, n_ents, argc, argv);
+}