tests: odb: allow passing fake objects to the fake backend

Right now, the fake backend is quite restrained in the way how it
works: we pass it an OID which it is to return later as well as an error
code we want it to return. While this is sufficient for existing tests,
we can make the fake backend a little bit more generic in order to allow
us testing for additional scenarios.

To do so, we change the backend to not accept an error code and OID
which it is to return for queries, but instead a simple array of OIDs
with their respective blob contents. On each query, the fake backend
simply iterates through this array and returns the first matching
object.
diff --git a/tests/odb/backend/backend_helpers.c b/tests/odb/backend/backend_helpers.c
index 21b33b9..2653702 100644
--- a/tests/odb/backend/backend_helpers.c
+++ b/tests/odb/backend/backend_helpers.c
@@ -2,83 +2,99 @@
 #include "git2/sys/odb_backend.h"
 #include "backend_helpers.h"
 
+static int search_object(const fake_object **out, fake_backend *fake, const git_oid *oid, size_t len)
+{
+	const fake_object *obj = fake->objects;
+
+	while (obj && obj->oid) {
+		git_oid current_oid;
+
+		git_oid_fromstr(&current_oid, obj->oid);
+
+		if (git_oid_ncmp(&current_oid, oid, len) == 0) {
+			if (out)
+				*out = obj;
+			return 0;
+		}
+
+		obj++;
+	}
+
+	return GIT_ENOTFOUND;
+}
+
 static int fake_backend__exists(git_odb_backend *backend, const git_oid *oid)
 {
 	fake_backend *fake;
 
-	GIT_UNUSED(oid);
-
 	fake = (fake_backend *)backend;
 
 	fake->exists_calls++;
 
-	return (fake->error_code == GIT_OK);
+	return search_object(NULL, fake, oid, GIT_OID_RAWSZ) == GIT_OK;
 }
 
 static int fake_backend__read(
 	void **buffer_p, size_t *len_p, git_otype *type_p,
 	git_odb_backend *backend, const git_oid *oid)
 {
+	const fake_object *obj;
 	fake_backend *fake;
 
-	GIT_UNUSED(buffer_p);
-	GIT_UNUSED(len_p);
-	GIT_UNUSED(type_p);
-	GIT_UNUSED(oid);
-
 	fake = (fake_backend *)backend;
 
 	fake->read_calls++;
 
-	*len_p = 0;
-	*buffer_p = NULL;
-	*type_p = GIT_OBJ_BLOB;
+	if (search_object(&obj, fake, oid, GIT_OID_RAWSZ) == 0) {
+		*len_p = strlen(obj->content);
+		*buffer_p = git__strdup(obj->content);
+		*type_p = GIT_OBJ_BLOB;
+		return 0;
+	}
 
-	return fake->error_code;
+	return GIT_ENOTFOUND;
 }
 
 static int fake_backend__read_header(
 	size_t *len_p, git_otype *type_p,
 	git_odb_backend *backend, const git_oid *oid)
 {
+	const fake_object *obj;
 	fake_backend *fake;
 
-	GIT_UNUSED(len_p);
-	GIT_UNUSED(type_p);
-	GIT_UNUSED(oid);
-
 	fake = (fake_backend *)backend;
 
 	fake->read_header_calls++;
 
-	*len_p = 0;
-	*type_p = GIT_OBJ_BLOB;
+	if (search_object(&obj, fake, oid, GIT_OID_RAWSZ) == 0) {
+		*len_p = strlen(obj->content);
+		*type_p = GIT_OBJ_BLOB;
+		return 0;
+	}
 
-	return fake->error_code;
+	return GIT_ENOTFOUND;
 }
 
 static int fake_backend__read_prefix(
 	git_oid *out_oid, void **buffer_p, size_t *len_p, git_otype *type_p,
 	git_odb_backend *backend, const git_oid *short_oid, size_t len)
 {
+	const fake_object *obj;
 	fake_backend *fake;
 
-	GIT_UNUSED(buffer_p);
-	GIT_UNUSED(len_p);
-	GIT_UNUSED(type_p);
-	GIT_UNUSED(short_oid);
-	GIT_UNUSED(len);
-
 	fake = (fake_backend *)backend;
 
 	fake->read_prefix_calls++;
 
-	git_oid_cpy(out_oid, &fake->oid);
-	*len_p = 0;
-	*buffer_p = NULL;
-	*type_p = GIT_OBJ_BLOB;
+	if (search_object(&obj, fake, short_oid, len) == 0) {
+		git_oid_fromstr(out_oid, obj->oid);
+		*len_p = strlen(obj->content);
+		*buffer_p = git__strdup(obj->content);
+		*type_p = GIT_OBJ_BLOB;
+		return 0;
+	}
 
-	return fake->error_code;
+	return GIT_ENOTFOUND;
 }
 
 static void fake_backend__free(git_odb_backend *_backend)
@@ -92,8 +108,7 @@
 
 int build_fake_backend(
 	git_odb_backend **out,
-	git_error_code error_code,
-	const git_oid *oid)
+	const fake_object *objects)
 {
 	fake_backend *backend;
 
@@ -103,7 +118,7 @@
 	backend->parent.version = GIT_ODB_BACKEND_VERSION;
 
 	backend->parent.refresh = NULL;
-	backend->error_code = error_code;
+	backend->objects = objects;
 
 	backend->parent.read = fake_backend__read;
 	backend->parent.read_prefix = fake_backend__read_prefix;
@@ -111,8 +126,6 @@
 	backend->parent.exists = fake_backend__exists;
 	backend->parent.free = &fake_backend__free;
 
-	git_oid_cpy(&backend->oid, oid);
-
 	*out = (git_odb_backend *)backend;
 
 	return 0;
diff --git a/tests/odb/backend/backend_helpers.h b/tests/odb/backend/backend_helpers.h
index 04bd844..6cc1ce9 100644
--- a/tests/odb/backend/backend_helpers.h
+++ b/tests/odb/backend/backend_helpers.h
@@ -1,18 +1,21 @@
 #include "git2/sys/odb_backend.h"
 
 typedef struct {
-	git_odb_backend parent;
+	const char *oid;
+	const char *content;
+} fake_object;
 
-	git_error_code error_code;
-	git_oid oid;
+typedef struct {
+	git_odb_backend parent;
 
 	int exists_calls;
 	int read_calls;
 	int read_header_calls;
 	int read_prefix_calls;
+
+	const fake_object *objects;
 } fake_backend;
 
 int build_fake_backend(
 	git_odb_backend **out,
-	git_error_code error_code,
-	const git_oid *oid);
+	const fake_object *objects);
diff --git a/tests/odb/backend/nonrefreshing.c b/tests/odb/backend/nonrefreshing.c
index 42da312..6abc0c6 100644
--- a/tests/odb/backend/nonrefreshing.c
+++ b/tests/odb/backend/nonrefreshing.c
@@ -5,22 +5,25 @@
 static git_repository *_repo;
 static fake_backend *_fake;
 
-#define HASH "deadbeefdeadbeefdeadbeefdeadbeefdeadbeef"
-#define EMPTY_HASH "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391"
+#define NONEXISTING_HASH "deadbeefdeadbeefdeadbeefdeadbeefdeadbeef"
+#define EXISTING_HASH "e69de29bb2d1d6434b8b29ae775ad8c2e48c5391"
 
-static git_oid _oid;
-static git_oid _empty_oid;
+static const fake_object _objects[] = {
+	{ EXISTING_HASH, "" },
+	{ NULL, NULL }
+};
 
-static void setup_repository_and_backend(git_error_code error_code, const char *hash)
+static git_oid _nonexisting_oid;
+static git_oid _existing_oid;
+
+static void setup_repository_and_backend(void)
 {
 	git_odb *odb = NULL;
 	git_odb_backend *backend = NULL;
-	git_oid oid;
 
 	_repo = cl_git_sandbox_init("testrepo.git");
 
-	cl_git_pass(git_oid_fromstr(&oid, hash));
-	cl_git_pass(build_fake_backend(&backend, error_code, &oid));
+	cl_git_pass(build_fake_backend(&backend, _objects));
 
 	cl_git_pass(git_repository_odb__weakptr(&odb, _repo));
 	cl_git_pass(git_odb_add_backend(odb, backend, 10));
@@ -30,8 +33,9 @@
 
 void test_odb_backend_nonrefreshing__initialize(void)
 {
-	git_oid_fromstr(&_oid, HASH);
-	git_oid_fromstr(&_empty_oid, EMPTY_HASH);
+	git_oid_fromstr(&_nonexisting_oid, NONEXISTING_HASH);
+	git_oid_fromstr(&_existing_oid, EXISTING_HASH);
+	setup_repository_and_backend();
 }
 
 void test_odb_backend_nonrefreshing__cleanup(void)
@@ -43,10 +47,8 @@
 {
 	git_odb *odb;
 
-	setup_repository_and_backend(GIT_ENOTFOUND, HASH);
-
 	cl_git_pass(git_repository_odb__weakptr(&odb, _repo));
-	cl_assert_equal_b(false, git_odb_exists(odb, &_oid));
+	cl_assert_equal_b(false, git_odb_exists(odb, &_nonexisting_oid));
 
 	cl_assert_equal_i(1, _fake->exists_calls);
 }
@@ -55,10 +57,8 @@
 {
 	git_object *obj;
 
-	setup_repository_and_backend(GIT_ENOTFOUND, HASH);
-
 	cl_git_fail_with(
-		git_object_lookup(&obj, _repo, &_oid, GIT_OBJ_ANY),
+		git_object_lookup(&obj, _repo, &_nonexisting_oid, GIT_OBJ_ANY),
 		GIT_ENOTFOUND);
 
 	cl_assert_equal_i(1, _fake->read_calls);
@@ -68,10 +68,8 @@
 {
 	git_object *obj;
 
-	setup_repository_and_backend(GIT_ENOTFOUND, HASH);
-
 	cl_git_fail_with(
-		git_object_lookup_prefix(&obj, _repo, &_oid, 7, GIT_OBJ_ANY),
+		git_object_lookup_prefix(&obj, _repo, &_nonexisting_oid, 7, GIT_OBJ_ANY),
 		GIT_ENOTFOUND);
 
 	cl_assert_equal_i(1, _fake->read_prefix_calls);
@@ -83,12 +81,10 @@
 	size_t len;
 	git_otype type;
 
-	setup_repository_and_backend(GIT_ENOTFOUND, HASH);
-
 	cl_git_pass(git_repository_odb__weakptr(&odb, _repo));
 
 	cl_git_fail_with(
-		git_odb_read_header(&len, &type, odb, &_oid),
+		git_odb_read_header(&len, &type, odb, &_nonexisting_oid),
 		GIT_ENOTFOUND);
 
 	cl_assert_equal_i(1, _fake->read_header_calls);
@@ -98,10 +94,8 @@
 {
 	git_odb *odb;
 
-	setup_repository_and_backend(GIT_OK, HASH);
-
 	cl_git_pass(git_repository_odb__weakptr(&odb, _repo));
-	cl_assert_equal_b(true, git_odb_exists(odb, &_oid));
+	cl_assert_equal_b(true, git_odb_exists(odb, &_existing_oid));
 
 	cl_assert_equal_i(1, _fake->exists_calls);
 }
@@ -110,9 +104,7 @@
 {
 	git_object *obj;
 
-	setup_repository_and_backend(GIT_OK, EMPTY_HASH);
-
-	cl_git_pass(git_object_lookup(&obj, _repo, &_empty_oid, GIT_OBJ_ANY));
+	cl_git_pass(git_object_lookup(&obj, _repo, &_existing_oid, GIT_OBJ_ANY));
 
 	cl_assert_equal_i(1, _fake->read_calls);
 
@@ -123,9 +115,7 @@
 {
 	git_object *obj;
 
-	setup_repository_and_backend(GIT_OK, EMPTY_HASH);
-
-	cl_git_pass(git_object_lookup_prefix(&obj, _repo, &_empty_oid, 7, GIT_OBJ_ANY));
+	cl_git_pass(git_object_lookup_prefix(&obj, _repo, &_existing_oid, 7, GIT_OBJ_ANY));
 
 	cl_assert_equal_i(1, _fake->read_prefix_calls);
 
@@ -138,11 +128,9 @@
 	size_t len;
 	git_otype type;
 
-	setup_repository_and_backend(GIT_OK, HASH);
-
 	cl_git_pass(git_repository_odb__weakptr(&odb, _repo));
 
-	cl_git_pass(git_odb_read_header(&len, &type, odb, &_oid));
+	cl_git_pass(git_odb_read_header(&len, &type, odb, &_existing_oid));
 
 	cl_assert_equal_i(1, _fake->read_header_calls);
 }
@@ -151,8 +139,6 @@
 {
 	git_object *obj;
 
-	setup_repository_and_backend(GIT_ENOTFOUND, HASH);
-
 	cl_git_fail_with(
 		git_revparse_single(&obj, _repo, "deadbeefdeadbeefdeadbeefdeadbeefdeadbeef"),
 		GIT_ENOTFOUND);