t: move reftable/basics_test.c to the unit testing framework

reftable/basics_test.c exercise the functions defined in
reftable/basics.{c, h}. Migrate reftable/basics_test.c to the
unit testing framework. Migration involves refactoring the tests
to use the unit testing framework instead of reftable's test
framework.

Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Chandra Pratap <chandrapratap3519@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/unit-tests/t-reftable-basics.c

@@ -0,0 +1,102 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#include "test-lib.h"
+#include "reftable/basics.h"
+
+struct integer_needle_lesseq_args {
+	int needle;
+	int *haystack;
+};
+
+static int integer_needle_lesseq(size_t i, void *_args)
+{
+	struct integer_needle_lesseq_args *args = _args;
+	return args->needle <= args->haystack[i];
+}
+
+static void test_binsearch(void)
+{
+	int haystack[] = { 2, 4, 6, 8, 10 };
+	struct {
+		int needle;
+		size_t expected_idx;
+	} testcases[] = {
+		{-9000, 0},
+		{-1, 0},
+		{0, 0},
+		{2, 0},
+		{3, 1},
+		{4, 1},
+		{7, 3},
+		{9, 4},
+		{10, 4},
+		{11, 5},
+		{9000, 5},
+	};
+
+	for (size_t i = 0; i < ARRAY_SIZE(testcases); i++) {
+		struct integer_needle_lesseq_args args = {
+			.haystack = haystack,
+			.needle = testcases[i].needle,
+		};
+		size_t idx;
+
+		idx = binsearch(ARRAY_SIZE(haystack), &integer_needle_lesseq, &args);
+		check_int(idx, ==, testcases[i].expected_idx);
+	}
+}
+
+static void test_names_length(void)
+{
+	char *a[] = { "a", "b", NULL };
+	check_int(names_length(a), ==, 2);
+}
+
+static void test_parse_names_normal(void)
+{
+	char in[] = "a\nb\n";
+	char **out = NULL;
+	parse_names(in, strlen(in), &out);
+	check_str(out[0], "a");
+	check_str(out[1], "b");
+	check(!out[2]);
+	free_names(out);
+}
+
+static void test_parse_names_drop_empty(void)
+{
+	char in[] = "a\n\n";
+	char **out = NULL;
+	parse_names(in, strlen(in), &out);
+	check_str(out[0], "a");
+	check(!out[1]);
+	free_names(out);
+}
+
+static void test_common_prefix(void)
+{
+	struct strbuf s1 = STRBUF_INIT;
+	struct strbuf s2 = STRBUF_INIT;
+	strbuf_addstr(&s1, "abcdef");
+	strbuf_addstr(&s2, "abc");
+	check_int(common_prefix_size(&s1, &s2), ==, 3);
+	strbuf_release(&s1);
+	strbuf_release(&s2);
+}
+
+int cmd_main(int argc, const char *argv[])
+{
+	TEST(test_common_prefix(), "common_prefix_size works");
+	TEST(test_parse_names_normal(), "parse_names works for basic input");
+	TEST(test_parse_names_drop_empty(), "parse_names drops empty string");
+	TEST(test_binsearch(), "binary search with binsearch works");
+	TEST(test_names_length(), "names_length retuns size of a NULL-terminated string array");
+
+	return test_done();
+}