tests - Add test_cpu_state

tests/test_cpu_state.cpp

@@ -0,0 +1,20 @@
+#include "doctest.h"
+
+#include "cpu/cpu.h"
+
+TEST_CASE("16-bit registers map to two 8-bit registers")
+{
+  Cpu_state c;
+
+  c.BC = 0xAA55;
+  CHECK(c.B == 0xAA);
+  CHECK(c.C == 0x55);
+
+  c.DE = 0x1122;
+  CHECK(c.D == 0x11);
+  CHECK(c.E == 0x22);
+
+  c.HL = 0x3344;
+  CHECK(c.H == 0x33);
+  CHECK(c.L == 0x44);
+}