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

src/system/nes/common.zig

@@ -0,0 +1,84 @@
+const std = @import("std");
+
+pub const screen_width: u16 = 256;
+pub const screen_height: u16 = 240;
+
+pub const Region = enum {
+    ntsc,
+    pal,
+
+    /// Native CPU clock frequency in Hz.
+    pub fn cpuClockRate(self: Region) u32 {
+        return switch (self) {
+            .ntsc => 1_789_773,
+            .pal => 1_662_607,
+        };
+    }
+
+    /// Total scanlines per frame (262 for NTSC, 312 for PAL).
+    pub fn totalScanlines(self: Region) u16 {
+        return switch (self) {
+            .ntsc => 262,
+            .pal => 312,
+        };
+    }
+
+    /// Scanline index of the pre-render scanline (261 for NTSC, 311 for PAL).
+    pub fn preRenderScanline(self: Region) u16 {
+        return switch (self) {
+            .ntsc => 261,
+            .pal => 311,
+        };
+    }
+
+    /// Number of VBlank scanlines.
+    pub fn vblankScanlines(self: Region) u16 {
+        return switch (self) {
+            .ntsc => 20,
+            .pal => 70,
+        };
+    }
+
+    /// CPU cycles to suppress PPU register writes after power/reset (~1 frame).
+    pub fn powerUpSuppressionCycles(self: Region) u32 {
+        return switch (self) {
+            .ntsc => 29_658,
+            .pal => 33_132,
+        };
+    }
+};
+
+/// Nametable mirroring mode used by PPU CIRAM and Cartridge mappers.
+pub const Mirroring = enum {
+    horizontal,
+    vertical,
+    single_screen_lower,
+    single_screen_upper,
+    four_screen,
+};
+
+/// Standard 8-button NES controller layout.
+pub const Button = enum(u8) {
+    a = 1 << 0,
+    b = 1 << 1,
+    select = 1 << 2,
+    start = 1 << 3,
+    up = 1 << 4,
+    down = 1 << 5,
+    left = 1 << 6,
+    right = 1 << 7,
+};
+
+test "region properties" {
+    const ntsc: Region = .ntsc;
+    try std.testing.expectEqual(@as(u32, 1_789_773), ntsc.cpuClockRate());
+    try std.testing.expectEqual(@as(u16, 262), ntsc.totalScanlines());
+    try std.testing.expectEqual(@as(u16, 261), ntsc.preRenderScanline());
+    try std.testing.expectEqual(@as(u32, 29_658), ntsc.powerUpSuppressionCycles());
+
+    const pal: Region = .pal;
+    try std.testing.expectEqual(@as(u32, 1_662_607), pal.cpuClockRate());
+    try std.testing.expectEqual(@as(u16, 312), pal.totalScanlines());
+    try std.testing.expectEqual(@as(u16, 311), pal.preRenderScanline());
+    try std.testing.expectEqual(@as(u32, 33_132), pal.powerUpSuppressionCycles());
+}