tests: odb: add more low-level backend tests

Introduce a new test suite "odb::backend::simple", which utilizes the
fake backend to exercise the ODB abstraction layer. While such tests
already exist for the case where multiple backends are put together, no
direct testing for functionality with a single backend exist yet.

tests/odb/backend/simple.c

+#include "clar_libgit2.h"
+#include "repository.h"
+#include "backend_helpers.h"
+
+#define EMPTY_HASH "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391"
+
+static git_repository *_repo;
+static git_odb *_odb;
+static git_odb_object *_obj;
+static git_oid _oid;
+
+static void setup_backend(const fake_object *objs)
+{
+	git_odb_backend *backend;
+
+	cl_git_pass(build_fake_backend(&backend, objs));
+
+	cl_git_pass(git_repository_odb__weakptr(&_odb, _repo));
+	cl_git_pass(git_odb_add_backend(_odb, backend, 10));
+}
+
+static void assert_object_contains(git_odb_object *obj, const char *expected)
+{
+	const char *actual = (const char *) git_odb_object_data(obj);
+
+	cl_assert_equal_s(actual, expected);
+}
+
+void test_odb_backend_simple__initialize(void)
+{
+	_repo = cl_git_sandbox_init("testrepo.git");
+	_odb = NULL;
+	_obj = NULL;
+}
+
+void test_odb_backend_simple__cleanup(void)
+{
+	git_odb_object_free(_obj);
+	cl_git_sandbox_cleanup();
+	cl_git_pass(git_libgit2_opts(GIT_OPT_ENABLE_STRICT_HASH_VERIFICATION, 1));
+}
+
+void test_odb_backend_simple__read_of_object_succeeds(void)
+{
+	const fake_object objs[] = {
+		{ "f6ea0495187600e7b2288c8ac19c5886383a4632", "foobar" },
+		{ NULL, NULL }
+	};
+
+	setup_backend(objs);
+
+	cl_git_pass(git_oid_fromstr(&_oid, objs[0].oid));
+	cl_git_pass(git_odb_read(&_obj, _odb, &_oid));
+
+	assert_object_contains(_obj, objs[0].content);
+}
+
+void test_odb_backend_simple__read_of_nonexisting_object_fails(void)
+{
+	const fake_object objs[] = {
+		{ "f6ea0495187600e7b2288c8ac19c5886383a4632", "foobar" },
+		{ NULL, NULL }
+	};
+
+	setup_backend(objs);
+
+	cl_git_pass(git_oid_fromstr(&_oid, "f6ea0495187600e7b2288c8ac19c5886383a4633"));
+	cl_git_fail_with(GIT_ENOTFOUND, git_odb_read(&_obj, _odb, &_oid));
+}
+
+void test_odb_backend_simple__read_with_hash_mismatch_fails(void)
+{
+	const fake_object objs[] = {
+		{ "1234567890123456789012345678901234567890", "nonmatching content" },
+		{ NULL, NULL }
+	};
+
+	setup_backend(objs);
+
+	cl_git_pass(git_oid_fromstr(&_oid, objs[0].oid));
+	cl_git_fail_with(GIT_EMISMATCH, git_odb_read(&_obj, _odb, &_oid));
+}
+
+void test_odb_backend_simple__read_with_hash_mismatch_succeeds_without_verification(void)
+{
+	const fake_object objs[] = {
+		{ "1234567890123456789012345678901234567890", "nonmatching content" },
+		{ NULL, NULL }
+	};
+
+	setup_backend(objs);
+	cl_git_pass(git_oid_fromstr(&_oid, objs[0].oid));
+
+	cl_git_pass(git_libgit2_opts(GIT_OPT_ENABLE_STRICT_HASH_VERIFICATION, 0));
+	cl_git_pass(git_odb_read(&_obj, _odb, &_oid));
+
+	assert_object_contains(_obj, objs[0].content);
+}
+
+void test_odb_backend_simple__read_prefix_succeeds(void)
+{
+	const fake_object objs[] = {
+		{ "f6ea0495187600e7b2288c8ac19c5886383a4632", "foobar" },
+		{ NULL, NULL }
+	};
+
+	setup_backend(objs);
+
+	cl_git_pass(git_oid_fromstr(&_oid, "f6ea0495187600e7b2288c8ac19c5886383a4632"));
+	cl_git_pass(git_odb_read(&_obj, _odb, &_oid));
+
+	assert_object_contains(_obj, objs[0].content);
+}
+
+void test_odb_backend_simple__read_prefix_of_nonexisting_object_fails(void)
+{
+	const fake_object objs[] = {
+		{ "f6ea0495187600e7b2288c8ac19c5886383a4632", "foobar" },
+		{ NULL, NULL }
+	};
+	char *hash = "f6ea0495187600e8";
+
+	setup_backend(objs);
+
+	cl_git_pass(git_oid_fromstrn(&_oid, hash, strlen(hash)));
+	cl_git_fail_with(GIT_ENOTFOUND, git_odb_read(&_obj, _odb, &_oid));
+}
+
+void test_odb_backend_simple__read_with_ambiguous_prefix_fails(void)
+{
+	const fake_object objs[] = {
+		{ "1234567890111111111111111111111111111111", "first content" },
+		{ "1234567890222222222222222222222222222222", "second content" },
+		{ NULL, NULL }
+	};
+
+	setup_backend(objs);
+
+	cl_git_pass(git_oid_fromstr(&_oid, objs[0].oid));
+	cl_git_fail_with(GIT_EAMBIGUOUS, git_odb_read_prefix(&_obj, _odb, &_oid, 7));
+}
+
+void test_odb_backend_simple__read_with_highly_ambiguous_prefix(void)
+{
+	const fake_object objs[] = {
+		{ "1234567890111111111111111111111111111111", "first content" },
+		{ "1234567890111111111111111111111111111112", "second content" },
+		{ NULL, NULL }
+	};
+
+	setup_backend(objs);
+
+	cl_git_pass(git_oid_fromstr(&_oid, objs[0].oid));
+	cl_git_pass(git_libgit2_opts(GIT_OPT_ENABLE_STRICT_HASH_VERIFICATION, 0));
+	cl_git_fail_with(GIT_EAMBIGUOUS, git_odb_read_prefix(&_obj, _odb, &_oid, 39));
+	cl_git_pass(git_odb_read_prefix(&_obj, _odb, &_oid, 40));
+	assert_object_contains(_obj, objs[0].content);
+}
+
+void test_odb_backend_simple__exists_succeeds(void)
+{
+	const fake_object objs[] = {
+		{ "f6ea0495187600e7b2288c8ac19c5886383a4632", "foobar" },
+		{ NULL, NULL }
+	};
+
+	setup_backend(objs);
+
+	cl_git_pass(git_oid_fromstr(&_oid, objs[0].oid));
+	cl_assert(git_odb_exists(_odb, &_oid));
+}
+
+void test_odb_backend_simple__exists_fails_for_nonexisting_object(void)
+{
+	const fake_object objs[] = {
+		{ "f6ea0495187600e7b2288c8ac19c5886383a4632", "foobar" },
+		{ NULL, NULL }
+	};
+
+	setup_backend(objs);
+
+	cl_git_pass(git_oid_fromstr(&_oid, "f6ea0495187600e7b2288c8ac19c5886383a4633"));
+	cl_assert(git_odb_exists(_odb, &_oid) == 0);
+}
+
+void test_odb_backend_simple__exists_prefix_succeeds(void)
+{
+	const fake_object objs[] = {
+		{ "1234567890111111111111111111111111111111", "first content" },
+		{ "1234567890222222222222222222222222222222", "second content" },
+		{ NULL, NULL }
+	};
+	git_oid found;
+
+	setup_backend(objs);
+
+	cl_git_pass(git_oid_fromstr(&_oid, objs[0].oid));
+	cl_git_pass(git_odb_exists_prefix(&found, _odb, &_oid, 12));
+	cl_assert(git_oid_equal(&found, &_oid));
+}
+
+void test_odb_backend_simple__exists_with_ambiguous_prefix_fails(void)
+{
+	const fake_object objs[] = {
+		{ "1234567890111111111111111111111111111111", "first content" },
+		{ "1234567890222222222222222222222222222222", "second content" },
+		{ NULL, NULL }
+	};
+
+	setup_backend(objs);
+
+	cl_git_pass(git_oid_fromstr(&_oid, objs[0].oid));
+	cl_git_fail_with(GIT_EAMBIGUOUS, git_odb_exists_prefix(NULL, _odb, &_oid, 7));
+}
+
+void test_odb_backend_simple__exists_with_highly_ambiguous_prefix(void)
+{
+	const fake_object objs[] = {
+		{ "1234567890111111111111111111111111111111", "first content" },
+		{ "1234567890111111111111111111111111111112", "second content" },
+		{ NULL, NULL }
+	};
+	git_oid found;
+
+	setup_backend(objs);
+
+	cl_git_pass(git_oid_fromstr(&_oid, objs[0].oid));
+	cl_git_pass(git_libgit2_opts(GIT_OPT_ENABLE_STRICT_HASH_VERIFICATION, 0));
+	cl_git_fail_with(GIT_EAMBIGUOUS, git_odb_exists_prefix(&found, _odb, &_oid, 39));
+	cl_git_pass(git_odb_exists_prefix(&found, _odb, &_oid, 40));
+	cl_assert(git_oid_equal(&found, &_oid));
+}