Add ABCIResults with Hash and Proof to State

State maintains LastResultsHash
Verify that we can produce unique hashes for each result,
and provide valid proofs from the root hash.

state/state_test.go

@@ -279,6 +279,40 @@ func TestConsensusParamsChangesSaveLoad(t *testing.T) {
 	}
 }
 
+func TestABCIResults(t *testing.T) {
+	a := ABCIResult{Code: 0, Data: nil}
+	b := ABCIResult{Code: 0, Data: []byte{}}
+	c := ABCIResult{Code: 0, Data: []byte("one")}
+	d := ABCIResult{Code: 14, Data: nil}
+	e := ABCIResult{Code: 14, Data: []byte("foo")}
+	f := ABCIResult{Code: 14, Data: []byte("bar")}
+
+	// nil and []byte{} should produce same hash
+	assert.Equal(t, a.Hash(), b.Hash())
+
+	// a and b should be the same, don't go in results
+	results := ABCIResults{a, c, d, e, f}
+
+	// make sure each result hashes properly
+	var last []byte
+	for i, res := range results {
+		h := res.Hash()
+		assert.NotEqual(t, last, h, "%d", i)
+		last = h
+	}
+
+	// make sure that we can get a root hash from results
+	// and verify proofs
+	root := results.Hash()
+	assert.NotEmpty(t, root)
+
+	for i, res := range results {
+		proof := results.ProveResult(i)
+		valid := proof.Verify(i, len(results), res.Hash(), root)
+		assert.True(t, valid, "%d", i)
+	}
+}
+
 func makeParams(blockBytes, blockTx, blockGas, txBytes,
 	txGas, partSize int) types.ConsensusParams {