Merge bitcoin#28857: test, refactor: Magic bytes array followup

1e5b861 test: Add test for array serialization (TheCharlatan)
d49d198 refactor: Initialize magic bytes in constructor initializer (TheCharlatan)

Pull request description:

  This is a followup-PR for bitcoin#28423

  * Initialize magic bytes in constructor
  * Add a small unit test for serializing arrays.

ACKs for top commit:
  sipa:
    utACK 1e5b861
  maflcko:
    lgtm ACK 1e5b861

Tree-SHA512: 0f58d2332dc501ca9fd419f40ed4f977c83dce0169e9a0eee1ffc9f8daa2d2ef7e7df18205ba076f55d90ae6c4a20d2b51ab303150d38470a962bcc58a66f6e7

Author: fanquake

src/test/serialize_tests.cpp

@@ -84,6 +84,8 @@ BOOST_AUTO_TEST_CASE(sizes)
     BOOST_CHECK_EQUAL(GetSerializeSize(int64_t(0), 0), 8U);
     BOOST_CHECK_EQUAL(GetSerializeSize(uint64_t(0), 0), 8U);
     BOOST_CHECK_EQUAL(GetSerializeSize(bool(0), 0), 1U);
+    BOOST_CHECK_EQUAL(GetSerializeSize(std::array<uint8_t, 1>{0}, 0), 1U);
+    BOOST_CHECK_EQUAL(GetSerializeSize(std::array<uint8_t, 2>{0, 0}, 0), 2U);
 }
 
 BOOST_AUTO_TEST_CASE(varints)
@@ -178,6 +180,16 @@ BOOST_AUTO_TEST_CASE(vector_bool)
     BOOST_CHECK(SerializeHash(vec1) == SerializeHash(vec2));
 }
 
+BOOST_AUTO_TEST_CASE(array)
+{
+    std::array<uint8_t, 32> array1{1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 0, 1, 0, 0, 1};
+    DataStream ds;
+    ds << array1;
+    std::array<uint8_t, 32> array2;
+    ds >> array2;
+    BOOST_CHECK(array1 == array2);
+}
+
 BOOST_AUTO_TEST_CASE(noncanonical)
 {
     // Write some non-canonical CompactSize encodings, and