Add some RAM and a stack

gb/stack_test.go

@@ -0,0 +1,59 @@
+package gb
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestStackPush(t *testing.T) {
+	cpu := createCPU([]byte{0x00, 0x00, 0x00})
+
+	cpu.StackPush(0xDE)
+
+	// Should decrement the stack pointer
+	assert.Equal(t, cpu.Regs.SP, uint16(0xDFFE))
+
+	// Should write the value to the stack
+	assert.Equal(t, cpu.Bus.Read(cpu.Regs.SP), byte(0xDE))
+}
+
+func TestStackPush16(t *testing.T) {
+	cpu := createCPU([]byte{0x00, 0x00, 0x00})
+
+	cpu.StackPush16(0xDEAD)
+
+	// Should decrement the stack pointer twice
+	assert.Equal(t, cpu.Regs.SP, uint16(0xDFFD))
+
+	// Should write the value to the stack
+	assert.Equal(t, cpu.Bus.Read16(cpu.Regs.SP), uint16(0xDEAD))
+}
+
+func TestStackPop(t *testing.T) {
+	cpu := createCPU([]byte{0x00, 0x00, 0x00})
+
+	cpu.StackPush(0xDE)
+
+	val := cpu.StackPop()
+
+	// Should increment the stack pointer
+	assert.Equal(t, cpu.Regs.SP, uint16(0xDFFF))
+
+	// Should return the byte value
+	assert.Equal(t, val, byte(0xDE))
+}
+
+func TestStackPop16(t *testing.T) {
+	cpu := createCPU([]byte{0x00, 0x00, 0x00})
+
+	cpu.StackPush16(0xBEEF)
+
+	val := cpu.StackPop16()
+
+	// Should increment the stack pointer
+	assert.Equal(t, cpu.Regs.SP, uint16(0xDFFF))
+
+	// Should return the 16 bit value
+	assert.Equal(t, val, uint16(0xBEEF))
+}