vm: fix basic VM tests

The tests now compile and won't panic for unexpected return values.

We need a recent-enough version of the mutan compiler because of
the new JUMPDEST requirements. Skip some tests if the installed mutan
version is too old. The debug VM test still fails, probably because
of an implementation bug.

vm/vm_test.go

@@ -14,22 +14,30 @@ import (
 	"github.com/ethereum/go-ethereum/ethstate"
 	"github.com/ethereum/go-ethereum/ethtrie"
 	"github.com/ethereum/go-ethereum/ethutil"
+	"github.com/obscuren/mutan"
 )
 
-type TestEnv struct {
+type TestEnv struct{}
+
+func (TestEnv) Origin() []byte        { return nil }
+func (TestEnv) BlockNumber() *big.Int { return nil }
+func (TestEnv) BlockHash() []byte     { return nil }
+func (TestEnv) PrevHash() []byte      { return nil }
+func (TestEnv) Coinbase() []byte      { return nil }
+func (TestEnv) Time() int64           { return 0 }
+func (TestEnv) GasLimit() *big.Int    { return nil }
+func (TestEnv) Difficulty() *big.Int  { return nil }
+func (TestEnv) Value() *big.Int       { return nil }
+func (TestEnv) AddLog(Log)            {}
+
+func (TestEnv) Transfer(from, to Account, amount *big.Int) error {
+	return nil
 }
 
-func (self TestEnv) Origin() []byte        { return nil }
-func (self TestEnv) BlockNumber() *big.Int { return nil }
-func (self TestEnv) BlockHash() []byte     { return nil }
-func (self TestEnv) PrevHash() []byte      { return nil }
-func (self TestEnv) Coinbase() []byte      { return nil }
-func (self TestEnv) Time() int64           { return 0 }
-func (self TestEnv) Difficulty() *big.Int  { return nil }
-func (self TestEnv) Value() *big.Int       { return nil }
-
 // This is likely to fail if anything ever gets looked up in the state trie :-)
-func (self TestEnv) State() *ethstate.State { return ethstate.New(ethtrie.New(nil, "")) }
+func (TestEnv) State() *ethstate.State {
+	return ethstate.New(ethtrie.New(nil, ""))
+}
 
 const mutcode = `
 var x = 0;
@@ -56,27 +64,35 @@ func setup(level ethlog.LogLevel, typ Type) (*Closure, VirtualMachine) {
 	return callerClosure, New(TestEnv{}, typ)
 }
 
+var big9 = ethutil.Hex2Bytes("0000000000000000000000000000000000000000000000000000000000000009")
+
 func TestDebugVm(t *testing.T) {
+	if mutan.Version < "0.6" {
+		t.Skip("skipping for mutan version", mutan.Version, " < 0.6")
+	}
+
 	closure, vm := setup(ethlog.DebugLevel, DebugVmTy)
 	ret, _, e := closure.Call(vm, nil)
 	if e != nil {
-		fmt.Println("error", e)
+		t.Fatalf("Call returned error: %v", e)
 	}
-
-	if ret[len(ret)-1] != 9 {
-		t.Errorf("Expected VM to return 9, got", ret, "instead.")
+	if !bytes.Equal(ret, big9) {
+		t.Errorf("Wrong return value '%x', want '%x'", ret, big9)
 	}
 }
 
 func TestVm(t *testing.T) {
+	if mutan.Version < "0.6" {
+		t.Skip("skipping for mutan version", mutan.Version, " < 0.6")
+	}
+
 	closure, vm := setup(ethlog.DebugLevel, StandardVmTy)
 	ret, _, e := closure.Call(vm, nil)
 	if e != nil {
-		fmt.Println("error", e)
+		t.Fatalf("Call returned error: %v", e)
 	}
-
-	if ret[len(ret)-1] != 9 {
-		t.Errorf("Expected VM to return 9, got", ret, "instead.")
+	if !bytes.Equal(ret, big9) {
+		t.Errorf("Wrong return value '%x', want '%x'", ret, big9)
 	}
 }