Add an instruction abstraction and visitor.

Change-Id: I5dc935831471296b6db1affef6e7ddcdddc82dde
diff --git a/src/dex_instruction_visitor_test.cc b/src/dex_instruction_visitor_test.cc
new file mode 100644
index 0000000..239e1eb
--- /dev/null
+++ b/src/dex_instruction_visitor_test.cc
@@ -0,0 +1,54 @@
+// Copyright 2011 Google Inc. All Rights Reserved.
+
+#include "src/dex_instruction_visitor.h"
+
+#include <iostream>
+#include "gtest/gtest.h"
+
+namespace art {
+
+class TestVisitor : public DexInstructionVisitor<TestVisitor> {};
+
+TEST(Instruction, Init) {
+  TestVisitor visitor;
+}
+
+class CountVisitor : public DexInstructionVisitor<CountVisitor> {
+ public:
+  int count_;
+
+  CountVisitor() : count_(0) {}
+
+  void Do_Default(Instruction* inst) {
+    ++count_;
+  }
+};
+
+TEST(Instruction, Count) {
+  CountVisitor v0;
+  uint16_t c0[] = {};
+  v0.Visit(c0, sizeof(c0));
+  EXPECT_EQ(0, v0.count_);
+
+  CountVisitor v1;
+  uint16_t c1[] = { 0 };
+  v1.Visit(c1, sizeof(c1));
+  EXPECT_EQ(1, v1.count_);
+
+  CountVisitor v2;
+  uint16_t c2[] = { 0, 0 };
+  v2.Visit(c2, sizeof(c2));
+  EXPECT_EQ(2, v2.count_);
+
+  CountVisitor v3;
+  uint16_t c3[] = { 0, 0, 0, };
+  v3.Visit(c3, sizeof(c3));
+  EXPECT_EQ(3, v3.count_);
+
+  CountVisitor v4;
+  uint16_t c4[] = { 0, 0, 0, 0  };
+  v4.Visit(c4, sizeof(c4));
+  EXPECT_EQ(4, v4.count_);
+}
+
+}  // namespace art