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

src/system/nes/mapper/mapper180.zig

@@ -0,0 +1,94 @@
+const std = @import("std");
+const common = @import("../common.zig");
+const Mirroring = common.Mirroring;
+
+// ponytail: Mapper 180 (Nichibutsu / Crazy Climber)
+// Fixed first 16KB at $8000-$BFFF, switchable 16KB at $C000-$FFFF via write to $8000-$FFFF.
+pub const Mapper180 = @This();
+
+prg_bank: u8 = 0,
+mirroring_mode: Mirroring,
+
+pub fn init(initial_mirroring: Mirroring) Mapper180 {
+    return .{ .mirroring_mode = initial_mirroring };
+}
+
+pub fn cpuRead(self: *const Mapper180, 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_16k_banks = @max(1, prg_rom.len / 0x4000);
+        var bank: usize = 0;
+
+        if (address < 0xc000) {
+            bank = 0;
+            const offset = address - 0x8000;
+            if (offset < prg_rom.len) return prg_rom[offset];
+        } else {
+            bank = @as(usize, self.prg_bank) % total_16k_banks;
+            const offset = (bank * 0x4000) + (address - 0xc000);
+            if (offset < prg_rom.len) return prg_rom[offset];
+        }
+        return 0;
+    }
+    return null;
+}
+
+pub fn cpuWrite(self: *Mapper180, 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;
+        }
+        return false;
+    }
+    if (address >= 0x8000 and address <= 0xffff) {
+        self.prg_bank = value & 0x0f;
+        return true;
+    }
+    return false;
+}
+
+pub fn ppuRead(_: *const Mapper180, 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 (chr_rom.len > 0) {
+            if (address < chr_rom.len) return chr_rom[address];
+        }
+        return 0;
+    }
+    return null;
+}
+
+pub fn ppuWrite(_: *Mapper180, 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 Mapper180) Mirroring {
+    return self.mirroring_mode;
+}
+
+pub fn irqLine(_: *const Mapper180) bool {
+    return false;
+}
+
+pub fn notifyPpuAddress(_: *Mapper180, _: u16) void {}
+
+test "mapper180 bank switching" {
+    var m = Mapper180.init(.horizontal);
+    var ram: [0x2000]u8 = undefined;
+
+    _ = m.cpuWrite(0x8000, 3, &ram);
+    try std.testing.expectEqual(@as(u8, 3), m.prg_bank);
+}