Add tests for InferDescriptor and Descriptor::IsSolvable

Author: sipa

src/script/sign.h

@@ -24,6 +24,11 @@ struct KeyOriginInfo
 {
     unsigned char fingerprint[4];
     std::vector<uint32_t> path;
+
+    friend bool operator==(const KeyOriginInfo& a, const KeyOriginInfo& b)
+    {
+        return std::equal(std::begin(a.fingerprint), std::end(a.fingerprint), std::begin(b.fingerprint)) && a.path == b.path;
+    }
 };
 
 /** An interface to be implemented by keystores that support signing. */

src/test/descriptor_tests.cpp

@@ -102,7 +102,19 @@ void Check(const std::string& prv, const std::string& pub, int flags, const std:
                     spend.vout.resize(1);
                     BOOST_CHECK_MESSAGE(SignSignature(Merge(keys_priv, script_provider), spks[n], spend, 0, 1, SIGHASH_ALL), prv);
                 }
+
+                /* Infer a descriptor from the generated script, and verify its solvability and that it roundtrips. */
+                auto inferred = InferDescriptor(spks[n], script_provider);
+                BOOST_CHECK_EQUAL(inferred->IsSolvable(), !(flags & UNSOLVABLE));
+                std::vector<CScript> spks_inferred;
+                FlatSigningProvider provider_inferred;
+                BOOST_CHECK(inferred->Expand(0, provider_inferred, spks_inferred, provider_inferred));
+                BOOST_CHECK_EQUAL(spks_inferred.size(), 1);
+                BOOST_CHECK(spks_inferred[0] == spks[n]);
+                BOOST_CHECK_EQUAL(IsSolvable(provider_inferred, spks_inferred[0]), !(flags & UNSOLVABLE));
+                BOOST_CHECK(provider_inferred.origins == script_provider.origins);
             }
+
             // Test whether the observed key path is present in the 'paths' variable (which contains expected, unobserved paths),
             // and then remove it from that set.
             for (const auto& origin : script_provider.origins) {