test(cpu): add Blargg hardware test ROM harness

tests/GameBoy.Core.Tests/BlarggTests.cs

@@ -0,0 +1,47 @@
+using Xunit;
+using Xunit.Abstractions;
+
+namespace GameBoy.Tests
+{
+    public sealed class BlarggTests
+    {
+        private const int MaxFrames = 4000;
+        private readonly ITestOutputHelper output;
+
+        public BlarggTests(ITestOutputHelper output)
+        {
+            this.output = output;
+        }
+
+        [Fact]
+        public void CpuInstrs_ReportsPassedOverSerial()
+        {
+            string serial = RunUntilSerialResult(TestRoms.Load("cpu_instrs.gb"));
+            output.WriteLine(serial);
+            Assert.Contains("Passed", serial);
+            Assert.DoesNotContain("Failed", serial);
+        }
+
+        [Fact]
+        public void InstrTiming_ReportsPassedOverSerial()
+        {
+            string serial = RunUntilSerialResult(TestRoms.Load("instr_timing.gb"));
+            output.WriteLine(serial);
+            Assert.Contains("Passed", serial);
+            Assert.DoesNotContain("Failed", serial);
+        }
+
+        private static string RunUntilSerialResult(byte[] rom)
+        {
+            var emulator = new Emulator(rom);
+            for (int frame = 0; frame < MaxFrames; frame++)
+            {
+                emulator.RunFrame();
+                string serial = emulator.SerialOutput;
+                if (serial.Contains("Passed") || serial.Contains("Failed"))
+                    return serial;
+            }
+            return emulator.SerialOutput;
+        }
+    }
+}