test(nes): consolidate and simplify inline subsystem unit tests

src/system/nes/mapper/axrom.zig

@@ -0,0 +1,76 @@
+const std = @import("std");
+const common = @import("../common.zig");
+const Mirroring = common.Mirroring;
+
+pub const Axrom = @This();
+
+prg_bank: u4 = 0,
+mirroring_mode: Mirroring = .single_screen_lower,
+
+pub fn init() Axrom {
+    return .{};
+}
+
+pub fn cpuRead(self: *const Axrom, address: u16, prg_rom: []const u8, prg_ram: []const u8) ?u8 {
+    if (address >= 0x6000 and address <= 0x7fff) {
+        const offset = address - 0x6000;
+        if (offset < prg_ram.len) return prg_ram[offset];
+        return 0;
+    }
+    if (address >= 0x8000 and address <= 0xffff) {
+        const total_32k_banks = @max(1, prg_rom.len / 0x8000);
+        const bank = @as(usize, self.prg_bank) % total_32k_banks;
+        const offset = (bank * 0x8000) + (address - 0x8000);
+        if (offset < prg_rom.len) return prg_rom[offset];
+        return 0;
+    }
+    return null;
+}
+
+pub fn cpuWrite(self: *Axrom, address: u16, value: u8, prg_ram: []u8) bool {
+    if (address >= 0x6000 and address <= 0x7fff) {
+        const offset = address - 0x6000;
+        if (offset < prg_ram.len) {
+            prg_ram[offset] = value;
+            return true;
+        }
+    }
+    if (address >= 0x8000 and address <= 0xffff) {
+        self.prg_bank = @truncate(value & 0x0f);
+        self.mirroring_mode = if ((value & 0x10) != 0) .single_screen_upper else .single_screen_lower;
+        return true;
+    }
+    return false;
+}
+
+pub fn ppuRead(_: *const Axrom, address: u16, chr_rom: []const u8, chr_ram: []const u8, chr_is_ram: bool) ?u8 {
+    if (address < 0x2000) {
+        if (chr_is_ram) {
+            if (address < chr_ram.len) return chr_ram[address];
+        } else {
+            if (address < chr_rom.len) return chr_rom[address];
+        }
+        return 0;
+    }
+    return null;
+}
+
+pub fn ppuWrite(_: *Axrom, address: u16, value: u8, chr_ram: []u8, chr_is_ram: bool) bool {
+    if (address < 0x2000 and chr_is_ram) {
+        if (address < chr_ram.len) {
+            chr_ram[address] = value;
+            return true;
+        }
+    }
+    return false;
+}
+
+pub fn mirroring(self: *const Axrom) Mirroring {
+    return self.mirroring_mode;
+}
+
+pub fn irqLine(_: *const Axrom) bool {
+    return false;
+}
+
+pub fn notifyPpuAddress(_: *Axrom, _: u16) void {}