first public release

r_register_prefix_tests.go

@@ -0,0 +1,19 @@
+package z80
+
+import "testing"
+
+// R must increment once per M1, including post-prefix opcode fetches.
+func TestR_Increments_On_DDCB(t *testing.T) {
+	cpu, mem, _ := testCPU()
+	cpu.IX = 0x2000
+	mem.WriteByte(0x2001, 0x01)
+	loadProgram(cpu, mem, 0x0000, 0xDD, 0xCB, 0x01, 0x06) // RLC (IX+1)
+	cpu.R = 0
+	r0 := cpu.R & 0x7F
+	mustStep(t, cpu)
+	r1 := cpu.R & 0x7F
+	inc := int((r1 - r0) & 0x7F)
+	if inc != 3 {
+		t.Fatalf("R should increment by 3 M1 cycles (DD, CB, op), got %d", inc)
+	}
+}