[protocol] Add unittest for libhoth_payload_update_read_chunk

This function is being used within libhoth host command and needs a
check.

Signed-off-by: Ellis Nguyen <sarzanguyen@google.com>

Author: esnguyen

protocol/payload_update_test.cc

@@ -16,8 +16,11 @@
 
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
+#include <unistd.h>
 
 #include <cstdint>
+#include <cstdlib>
+#include <cstring>
 #include <memory>
 
 #include "command_version.h"
@@ -47,6 +50,16 @@ MATCHER_P2(IsEraseRequest, offset, len, "") {
          p->len == static_cast<uint32_t>(len);
 }
 
+MATCHER_P2(IsReadRequest, offset, len, "") {
+  const uint8_t* data = static_cast<const uint8_t*>(arg);
+  const struct payload_update_packet* p =
+      reinterpret_cast<const struct payload_update_packet*>(
+          data + sizeof(struct hoth_host_request));
+  return p->type == PAYLOAD_UPDATE_READ &&
+         p->offset == static_cast<uint32_t>(offset) &&
+         p->len == static_cast<uint32_t>(len);
+}
+
 TEST_F(LibHothTest, payload_update_bad_image_test) {
   EXPECT_CALL(mock_, send(_, UsesCommand(kCmd), _))
       .WillRepeatedly(Return(LIBHOTH_OK));
@@ -496,3 +509,29 @@ TEST_F(LibHothTest, payload_update_erase_cmd_range_overflow_test) {
   EXPECT_EQ(libhoth_payload_update_erase(&hoth_dev_, kOffset, kSize),
             PAYLOAD_UPDATE_INVALID_ARGS);
 }
+
+TEST_F(LibHothTest, payload_update_read_chunk_test) {
+  uint8_t expected_data[] = {0x11, 0x22, 0x33, 0x44, 0x55};
+  size_t offset = 0x100;
+  size_t len = sizeof(expected_data);
+
+  EXPECT_CALL(mock_, send(_, IsReadRequest(offset, len), _))
+      .WillOnce(Return(LIBHOTH_OK));
+  EXPECT_CALL(mock_, receive)
+      .WillOnce(DoAll(CopyResp(expected_data, len), Return(LIBHOTH_OK)));
+
+  char temp_path[] = "/tmp/libhoth_payload_read_XXXXXX";
+  int fd = mkstemp(temp_path);
+  ASSERT_GE(fd, 0);
+
+  EXPECT_EQ(libhoth_payload_update_read_chunk(&hoth_dev_, fd, len, offset),
+            PAYLOAD_UPDATE_OK);
+
+  lseek(fd, 0, SEEK_SET);
+  uint8_t actual_data[sizeof(expected_data)] = {0};
+  ASSERT_EQ(read(fd, actual_data, len), static_cast<ssize_t>(len));
+  EXPECT_THAT(actual_data, ::testing::ElementsAreArray(expected_data));
+
+  close(fd);
+  unlink(temp_path);
+}