Added simple test case for arithmetic

creature_test.go

@@ -0,0 +1,56 @@
+package creature
+
+import "testing"
+
+func TestArithmetic(test *testing.T) {
+	machine := Machine {
+		Program: []int {
+			0x0, 2,
+			0x0, 3,
+			0x4,
+			
+			0x0, 10,
+			0x0, 4,
+			0x5,
+			
+			0x0, 7,
+			0x0, 2,
+			0x6,
+			
+			0x0, 12,
+			0x0, 3,
+			0x7,
+		},
+	}
+
+	machine.Execute(0)
+	addResult := machine.Pop()
+	subResult := machine.Pop()
+	mulResult := machine.Pop()
+	divResult := machine.Pop()
+
+	test.Log("add:", addResult)
+	test.Log("sub:", subResult)
+	test.Log("mul:", mulResult)
+	test.Log("div:", divResult)
+
+	if addResult != 5 {
+		test.Log("add result should be", 5)
+		test.Fail()
+	}
+
+	if subResult != 6 {
+		test.Log("sub result should be", 6)
+		test.Fail()
+	}
+
+	if mulResult != 14 {
+		test.Log("mul result should be", 14)
+		test.Fail()
+	}
+
+	if divResult != 4 {
+		test.Log("div result should be", 4)
+		test.Fail()
+	}
+}