test: remove test-only arith_uint256S

Tests that are solely testing constructing from a hex string
are dropped, others are modified to use a uint256 constructor
or the arith_uint256 uint64_t constructor.

Since an arith_uint256 can not be constructed from a string
directly, we need to ensure that test coverage on
UintToArith256(uint256::FromHex()) is not reduced.
uint256::FromHex() already has good test coverage, but
the test coverage on UintToArith256() and ArithToUint256()
is increased in this commit by upgrading the `conversion`
test case.

Moreover, since `uint256.h` does not have any dependencies
on `arith_uint256.h`, the conversion tests are moved to
`arith_uint256_tests.cpp` so the dependency can be cleaned
up entirely in a future commit.

Author: stickies-v

src/test/arith_uint256_tests.cpp

@@ -23,9 +23,6 @@ static inline arith_uint256 arith_uint256V(const std::vector<unsigned char>& vch
 {
     return UintToArith256(uint256(vch));
 }
-// Takes a number written in hex (with most significant digits first).
-static inline arith_uint256 arith_uint256S(std::string_view str) { return UintToArith256(uint256S(str)); }
-
 const unsigned char R1Array[] =
     "\x9c\x52\x4a\xdb\xcf\x56\x11\x12\x2b\x29\x12\x5e\x5d\x35\xd2\xd2"
     "\x22\x81\xaa\xb5\x33\xf0\x08\x32\xd5\x56\xb1\xf9\xea\xe5\x1d\x7d";
@@ -39,8 +36,6 @@ const unsigned char R2Array[] =
     "\x13\x30\x47\xa3\x19\x2d\xda\x71\x49\x13\x72\xf0\xb4\xca\x81\xd7";
 const arith_uint256 R2L = arith_uint256V(std::vector<unsigned char>(R2Array,R2Array+32));
 
-const char R1LplusR2L[] = "549FB09FEA236A1EA3E31D4D58F1B1369288D204211CA751527CFC175767850C";
-
 const unsigned char ZeroArray[] =
     "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
     "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00";
@@ -97,27 +92,25 @@ BOOST_AUTO_TEST_CASE( basics ) // constructors, equality, inequality
     }
     BOOST_CHECK(ZeroL == (OneL << 256));
 
-    // String Constructor and Copy Constructor
-    BOOST_CHECK(arith_uint256S("0x" + R1L.ToString()) == R1L);
-    BOOST_CHECK(arith_uint256S("0x" + R2L.ToString()) == R2L);
-    BOOST_CHECK(arith_uint256S("0x" + ZeroL.ToString()) == ZeroL);
-    BOOST_CHECK(arith_uint256S("0x" + OneL.ToString()) == OneL);
-    BOOST_CHECK(arith_uint256S("0x" + MaxL.ToString()) == MaxL);
-    BOOST_CHECK(arith_uint256S(R1L.ToString()) == R1L);
-    BOOST_CHECK(arith_uint256S("   0x" + R1L.ToString() + "   ") == R1L);
-    BOOST_CHECK(arith_uint256S("") == ZeroL);
-    BOOST_CHECK(arith_uint256S("1") == OneL);
-    BOOST_CHECK(R1L == arith_uint256S(R1ArrayHex));
+    // Construct from hex string
+    BOOST_CHECK_EQUAL(UintToArith256(uint256::FromHex(R1L.ToString()).value()), R1L);
+    BOOST_CHECK_EQUAL(UintToArith256(uint256::FromHex(R2L.ToString()).value()), R2L);
+    BOOST_CHECK_EQUAL(UintToArith256(uint256::FromHex(ZeroL.ToString()).value()), ZeroL);
+    BOOST_CHECK_EQUAL(UintToArith256(uint256::FromHex(OneL.ToString()).value()), OneL);
+    BOOST_CHECK_EQUAL(UintToArith256(uint256::FromHex(MaxL.ToString()).value()), MaxL);
+    BOOST_CHECK_EQUAL(UintToArith256(uint256::FromHex(R1ArrayHex).value()), R1L);
+
+    // Copy constructor
     BOOST_CHECK(arith_uint256(R1L) == R1L);
     BOOST_CHECK((arith_uint256(R1L^R2L)^R2L) == R1L);
     BOOST_CHECK(arith_uint256(ZeroL) == ZeroL);
     BOOST_CHECK(arith_uint256(OneL) == OneL);
 
     // uint64_t constructor
-    BOOST_CHECK((R1L & arith_uint256S("0xffffffffffffffff")) == arith_uint256(R1LLow64));
-    BOOST_CHECK(ZeroL == arith_uint256(0));
-    BOOST_CHECK(OneL == arith_uint256(1));
-    BOOST_CHECK(arith_uint256S("0xffffffffffffffff") == arith_uint256(0xffffffffffffffffULL));
+    BOOST_CHECK_EQUAL(R1L & arith_uint256{0xffffffffffffffff}, arith_uint256{R1LLow64});
+    BOOST_CHECK_EQUAL(ZeroL, arith_uint256{0});
+    BOOST_CHECK_EQUAL(OneL, arith_uint256{1});
+    BOOST_CHECK_EQUAL(arith_uint256{0xffffffffffffffff}, arith_uint256{0xffffffffffffffffULL});
 
     // Assignment (from base_uint)
     arith_uint256 tmpL = ~ZeroL; BOOST_CHECK(tmpL == ~ZeroL);
@@ -284,15 +277,12 @@ BOOST_AUTO_TEST_CASE( comparison ) // <= >= < >
 
     BOOST_CHECK_LT(ZeroL,
                    OneL);
-    // Verify hex number representation has the most significant digits first.
-    BOOST_CHECK_LT(arith_uint256S("0000000000000000000000000000000000000000000000000000000000000001"),
-                   arith_uint256S("1000000000000000000000000000000000000000000000000000000000000000"));
 }
 
 BOOST_AUTO_TEST_CASE( plusMinus )
 {
     arith_uint256 TmpL = 0;
-    BOOST_CHECK(R1L + R2L == arith_uint256S(R1LplusR2L));
+    BOOST_CHECK_EQUAL(R1L + R2L, UintToArith256(uint256{"549fb09fea236a1ea3e31d4d58f1b1369288d204211ca751527cfc175767850c"}));
     TmpL += R1L;
     BOOST_CHECK(TmpL == R1L);
     TmpL += R2L;
@@ -356,8 +346,8 @@ BOOST_AUTO_TEST_CASE( multiply )
 
 BOOST_AUTO_TEST_CASE( divide )
 {
-    arith_uint256 D1L{arith_uint256S("AD7133AC1977FA2B7")};
-    arith_uint256 D2L{arith_uint256S("ECD751716")};
+    arith_uint256 D1L{UintToArith256(uint256{"00000000000000000000000000000000000000000000000ad7133ac1977fa2b7"})};
+    arith_uint256 D2L{UintToArith256(uint256{"0000000000000000000000000000000000000000000000000000000ecd751716"})};
     BOOST_CHECK((R1L / D1L).ToString() == "00000000000000000b8ac01106981635d9ed112290f8895545a7654dde28fb3a");
     BOOST_CHECK((R1L / D2L).ToString() == "000000000873ce8efec5b67150bad3aa8c5fcb70e947586153bf2cec7c37c57a");
     BOOST_CHECK(R1L / OneL == R1L);
@@ -571,4 +561,21 @@ BOOST_AUTO_TEST_CASE( getmaxcoverage ) // some more tests just to get 100% cover
     CHECKBITWISEOPERATOR(R1,~R2,&)
 }
 
+BOOST_AUTO_TEST_CASE(conversion)
+{
+    for (const arith_uint256& arith : {ZeroL, OneL, R1L, R2L}) {
+        const auto u256{uint256::FromHex(arith.GetHex()).value()};
+        BOOST_CHECK_EQUAL(UintToArith256(ArithToUint256(arith)), arith);
+        BOOST_CHECK_EQUAL(UintToArith256(u256), arith);
+        BOOST_CHECK_EQUAL(u256, ArithToUint256(arith));
+        BOOST_CHECK_EQUAL(ArithToUint256(arith).GetHex(), UintToArith256(u256).GetHex());
+    }
+
+    for (uint8_t num : {0, 1, 0xff}) {
+        BOOST_CHECK_EQUAL(UintToArith256(uint256{num}), arith_uint256{num});
+        BOOST_CHECK_EQUAL(uint256{num}, ArithToUint256(arith_uint256{num}));
+        BOOST_CHECK_EQUAL(UintToArith256(uint256{num}), num);
+    }
+}
+
 BOOST_AUTO_TEST_SUITE_END()

src/test/uint256_tests.cpp

@@ -264,22 +264,6 @@ BOOST_AUTO_TEST_CASE(methods) // GetHex SetHexDeprecated FromHex begin() end() s
     ss.clear();
 }
 
-BOOST_AUTO_TEST_CASE( conversion )
-{
-    BOOST_CHECK_EQUAL(ArithToUint256(UintToArith256(ZeroL)), ZeroL);
-    BOOST_CHECK_EQUAL(ArithToUint256(UintToArith256(OneL)), OneL);
-    BOOST_CHECK_EQUAL(ArithToUint256(UintToArith256(R1L)), R1L);
-    BOOST_CHECK_EQUAL(ArithToUint256(UintToArith256(R2L)), R2L);
-    BOOST_CHECK_EQUAL(UintToArith256(ZeroL), 0);
-    BOOST_CHECK_EQUAL(UintToArith256(OneL), 1);
-    BOOST_CHECK_EQUAL(ArithToUint256(0), ZeroL);
-    BOOST_CHECK_EQUAL(ArithToUint256(1), OneL);
-    BOOST_CHECK_EQUAL(arith_uint256(UintToArith256(uint256S(R1L.GetHex()))), UintToArith256(R1L));
-    BOOST_CHECK_EQUAL(arith_uint256(UintToArith256(uint256S(R2L.GetHex()))), UintToArith256(R2L));
-    BOOST_CHECK_EQUAL(R1L.GetHex(), UintToArith256(R1L).GetHex());
-    BOOST_CHECK_EQUAL(R2L.GetHex(), UintToArith256(R2L).GetHex());
-}
-
 BOOST_AUTO_TEST_CASE( operator_with_self )
 {