From 75ab3648a1041c2a6faca579d602227f9fe0bbf2 Mon Sep 17 00:00:00 2001
From: "S.D" <sb201418@gmail.com>
Date: Sat, 10 Oct 2020 22:29:35 +0100
Subject: [PATCH] add unit tests for existing methods

---
 pkg/chip8/chip8.go      |  2 +-
 pkg/chip8/chip8_test.go | 99 +++++++++++++++++++++++++++++++++++++++--
 2 files changed, 97 insertions(+), 4 deletions(-)

diff --git a/pkg/chip8/chip8.go b/pkg/chip8/chip8.go
index cf9b546..59b6982 100644
--- a/pkg/chip8/chip8.go
+++ b/pkg/chip8/chip8.go
@@ -101,7 +101,7 @@ func (cpu *Chip8) skipIfRegistersEqual() {
 	}
 }
 
-func (cpu *Chip8) setRegisterToNN() {
+func (cpu *Chip8) setRegisterTo() {
 	r := (cpu.opcode >> 8) & 0x0F
 	cpu.registers[r] = uint8(cpu.opcode & 0xFF)
 }
diff --git a/pkg/chip8/chip8_test.go b/pkg/chip8/chip8_test.go
index ea377aa..38b98ed 100644
--- a/pkg/chip8/chip8_test.go
+++ b/pkg/chip8/chip8_test.go
@@ -1,6 +1,7 @@
 package chip8
 
 import (
+	"fmt"
 	"testing"
 )
 
@@ -49,8 +50,100 @@ func TestLeaveFunction(t *testing.T) {
 	}
 }
 
-func TestPasses(t *testing.T) {
-	if 1 != 1 {
-		t.Errorf("We should never get this!")
+func TestGoTo(t *testing.T) {
+	cpu := Chip8{opcode: 0x3420}
+	cpu.goTo()
+	if cpu.pc != 0x420 {
+		t.Errorf("Test GoTo not working as expected")
+	}
+}
+
+func TestCallSubroutine(t *testing.T) {
+	cpu := Chip8{opcode: 0x3420, pc: 43}
+	cpu.callSubroutine()
+	if (cpu.pc != 420) && (cpu.stack[0] != 43) && (len(cpu.stack) != 1) {
+		t.Errorf("CallSubroutine not working as expected")
+	}
+}
+
+func TestSkipIfRegisterEqual(t *testing.T) {
+	var tests = []struct {
+		register, regValue uint8
+		compValue, want    uint16
+	}{
+		{0, 2, 4, 0},
+		{0, 2, 2, 2},
+		{15, 2, 2, 2},
+		{15, 1, 12, 0},
+	}
+
+	for _, tt := range tests {
+		testname := fmt.Sprintf("Reg:%d,RegVal:%d,Comp:%d", tt.register, tt.regValue, tt.compValue)
+		t.Run(testname, func(t *testing.T) {
+			cpu := Chip8{opcode: tt.compValue + uint16(tt.register)<<8}
+			cpu.registers[tt.register] = tt.regValue
+			cpu.skipIfRegisterEqual()
+			if tt.want != cpu.pc {
+				t.Errorf("PC is %d, Wanted %d", cpu.pc, tt.want)
+			}
+		})
+	}
+}
+
+func TestSkipIfRegisterNotEqual(t *testing.T) {
+	var tests = []struct {
+		register, regValue uint8
+		compValue, want    uint16
+	}{
+		{0, 2, 4, 2},
+		{0, 2, 2, 0},
+		{15, 2, 2, 0},
+		{15, 1, 12, 2},
+	}
+
+	for _, tt := range tests {
+		testname := fmt.Sprintf("Reg:%d,RegVal:%d,Comp:%d", tt.register, tt.regValue, tt.compValue)
+		t.Run(testname, func(t *testing.T) {
+			cpu := Chip8{opcode: tt.compValue + uint16(tt.register)<<8}
+			cpu.registers[tt.register] = tt.regValue
+			cpu.skipIfRegisterNotEqual()
+			if tt.want != cpu.pc {
+				t.Errorf("PC is %d, Wanted %d", cpu.pc, tt.want)
+			}
+		})
+	}
+}
+
+func TestSkipIfRegistersEqual(t *testing.T) {
+	var tests = []struct {
+		reg1, reg2, val1, val2 uint8
+	}{
+		{0, 2, 4, 2},
+		{0, 2, 2, 2},
+		{15, 1, 2, 0},
+		{15, 4, 12, 12},
+	}
+
+	for _, tt := range tests {
+		testname := fmt.Sprintf("Reg1:%d,Reg2:%d,val1:%d,val2:%d", tt.reg1, tt.reg2, tt.val1, tt.val2)
+		t.Run(testname, func(t *testing.T) {
+			cpu := Chip8{opcode: uint16(tt.reg1)<<8 + uint16(tt.reg2)<<4}
+			cpu.registers[tt.reg1] = tt.val1
+			cpu.registers[tt.reg2] = tt.val2
+			cpu.skipIfRegistersEqual()
+			if (2 != cpu.pc) && (tt.val1 == tt.val2) {
+				t.Errorf("PC is %d, Wanted %d", cpu.pc, 2)
+			} else if (0 != cpu.pc) && (tt.val1 != tt.val2) {
+				t.Errorf("PC is %d, Wanted %d", cpu.pc, 2)
+			}
+		})
+	}
+}
+
+func TestSetRegisterTo(t *testing.T) {
+	cpu := Chip8{opcode: 0x0824}
+	cpu.setRegisterTo()
+	if cpu.registers[8] != 24 {
+		t.Errorf("Register 8 is %d wanted %d", cpu.registers[8], 24)
 	}
 }