From baf9d2b76850fb184f30680a06704d996d999468 Mon Sep 17 00:00:00 2001
From: BlockChainDev <kevtheappdev@gmail.com>
Date: Fri, 15 Mar 2019 22:42:35 +0000
Subject: [PATCH] - Add test for math `Add` opcode - basic opcode execution

---
 pkg/vm/state.go             | 10 ++++++++++
 pkg/vm/vm.go                | 38 ++++++++++++++++++++++++++++++++++++
 pkg/vm/vm_ops_maths_test.go | 39 +++++++++++++++++++++++++++++++++++++
 3 files changed, 87 insertions(+)
 create mode 100644 pkg/vm/state.go
 create mode 100644 pkg/vm/vm.go
 create mode 100644 pkg/vm/vm_ops_maths_test.go

diff --git a/pkg/vm/state.go b/pkg/vm/state.go
new file mode 100644
index 000000000..4090ec86e
--- /dev/null
+++ b/pkg/vm/state.go
@@ -0,0 +1,10 @@
+package vm
+
+type vmstate byte
+
+const (
+	NONE  = 0
+	HALT  = 1 << 0
+	FAULT = 1 << 1
+	BREAK = 1 << 2
+)
diff --git a/pkg/vm/vm.go b/pkg/vm/vm.go
new file mode 100644
index 000000000..1793be031
--- /dev/null
+++ b/pkg/vm/vm.go
@@ -0,0 +1,38 @@
+package vm
+
+import (
+	"fmt"
+
+	"github.com/CityOfZion/neo-go/pkg/vm/stack"
+)
+
+// VM represents an instance of a Neo Virtual Machine
+type VM struct {
+	InvocationStack stack.Invocation
+	state           vmstate
+}
+
+//NewVM loads in a script
+// uses the script to initiate a Context object
+// pushes the context to the invocation stack
+func NewVM(script []byte) *VM {
+	ctx := stack.NewContext(script)
+	v := &VM{
+		state: NONE,
+	}
+	v.InvocationStack.Push(ctx)
+	return v
+}
+
+// ExecuteOp will execute one opcode for a given context
+func (v *VM) ExecuteOp(op stack.Instruction, ctx *stack.Context) error {
+	handleOp, ok := opFunc[op]
+	if !ok {
+		return fmt.Errorf("unknown opcode entered %v", op)
+	}
+	err := handleOp(ctx, &v.InvocationStack)
+	if err != nil {
+		return err
+	}
+	return nil
+}
diff --git a/pkg/vm/vm_ops_maths_test.go b/pkg/vm/vm_ops_maths_test.go
new file mode 100644
index 000000000..a9d80373a
--- /dev/null
+++ b/pkg/vm/vm_ops_maths_test.go
@@ -0,0 +1,39 @@
+package vm
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/CityOfZion/neo-go/pkg/vm/stack"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAddOp(t *testing.T) {
+
+	v := VM{}
+
+	a, err := stack.NewInt(big.NewInt(20))
+	if err != nil {
+		t.Fail()
+	}
+	b, err := stack.NewInt(big.NewInt(23))
+	if err != nil {
+		t.Fail()
+	}
+
+	ctx := stack.NewContext([]byte{})
+	ctx.Estack.Push(a).Push(b)
+
+	v.ExecuteOp(stack.ADD, ctx)
+
+	// Stack should have one item
+	assert.Equal(t, 1, ctx.Estack.Len())
+
+	item, err := ctx.Estack.PopInt()
+	if err != nil {
+		t.Fail()
+	}
+
+	assert.Equal(t, int64(43), item.Value().Int64())
+
+}