test: gtest for Sapling encoding and decoding

src/Makefile.gtest.include

@@ -23,6 +23,7 @@ zcash_gtest_SOURCES += \
 	gtest/test_equihash.cpp \
 	gtest/test_httprpc.cpp \
 	gtest/test_joinsplit.cpp \
+	gtest/test_keys.cpp \
 	gtest/test_keystore.cpp \
 	gtest/test_noteencryption.cpp \
 	gtest/test_mempool.cpp \

src/gtest/test_keys.cpp

@@ -0,0 +1,42 @@
+#include <chainparams.h>
+#include <key_io.h>
+#include <zcash/Address.hpp>
+
+#include <gtest/gtest.h>
+
+TEST(Keys, EncodeAndDecodeSapling)
+{
+    SelectParams(CBaseChainParams::MAIN);
+
+    for (size_t i = 0; i < 1000; i++) {
+        auto sk = libzcash::SaplingSpendingKey::random();
+        {
+            std::string sk_string = EncodeSpendingKey(sk);
+            EXPECT_EQ(
+                sk_string.substr(0, 24),
+                Params().Bech32HRP(CChainParams::SAPLING_SPENDING_KEY));
+
+            auto spendingkey2 = DecodeSpendingKey(sk_string);
+            EXPECT_TRUE(IsValidSpendingKey(spendingkey2));
+
+            ASSERT_TRUE(boost::get<libzcash::SaplingSpendingKey>(&spendingkey2) != nullptr);
+            auto sk2 = boost::get<libzcash::SaplingSpendingKey>(spendingkey2);
+            EXPECT_EQ(sk, sk2);
+        }
+        {
+            auto addr = sk.default_address();
+
+            std::string addr_string = EncodePaymentAddress(addr);
+            EXPECT_EQ(
+                addr_string.substr(0, 2),
+                Params().Bech32HRP(CChainParams::SAPLING_PAYMENT_ADDRESS));
+
+            auto paymentaddr2 = DecodePaymentAddress(addr_string);
+            EXPECT_TRUE(IsValidPaymentAddress(paymentaddr2));
+
+            ASSERT_TRUE(boost::get<libzcash::SaplingPaymentAddress>(&paymentaddr2) != nullptr);
+            auto addr2 = boost::get<libzcash::SaplingPaymentAddress>(paymentaddr2);
+            EXPECT_EQ(addr, addr2);
+        }
+    }
+}