tests - Add first interrupt tests

tests/test_cpu_interrupts.cpp

@@ -0,0 +1,68 @@
+#include "doctest.h"
+
+#include "cpu/cpu.h"
+#include "memory/ram.h"
+
+TEST_CASE("EI followed by DI should not trigger interrupt")
+{
+  u8 test_ram[] = {
+    0xFB, // EI
+    0xF3, // DI
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  };
+  RAM r(test_ram, 0x20, true);
+  Cpu cpu(&r);
+
+  cpu.state.IE = 0x1F; // Enable all types of interrupts
+  cpu.state.IF = 0x1F; // All interrupts pending
+
+  CHECK(cpu.state.PC == 0x0);
+  CHECK(cpu.state.IME == IME_OFF);
+
+  cpu.step();
+
+  CHECK(cpu.state.PC == 0x1);
+  CHECK(cpu.state.IME == IME_SCHEDULED);
+
+  cpu.step();
+
+  CHECK(cpu.state.PC == 0x2);
+  CHECK(cpu.state.IME == IME_OFF);
+
+  cpu.step();
+
+  CHECK(cpu.state.PC == 0x3);
+  CHECK(cpu.state.IME == IME_OFF);
+}
+
+TEST_CASE("interrupt triggers call to correct ISR")
+{
+  RAM r(0x100);
+  Cpu cpu(&r);
+
+  cpu.state.IME = IME_ON;
+  cpu.state.IE = INT_MASK;
+
+  InterruptType it;
+  u8 expected_pc;
+
+  SUBCASE("VBlank")  { it = INT_VBlank;  expected_pc = 0x40; }
+  SUBCASE("LCDSTAT") { it = INT_LCDSTAT; expected_pc = 0x48; }
+  SUBCASE("Timer")   { it = INT_Timer;   expected_pc = 0x50; }
+  SUBCASE("Serial")  { it = INT_Serial;  expected_pc = 0x58; }
+  SUBCASE("Joypad")  { it = INT_Joypad;  expected_pc = 0x60; }
+
+  cpu.signalInterrupt(it);
+
+  CHECK(cpu.state.IF == it);
+
+  cpu.step();
+
+  CHECK(cpu.state.IF == 0);
+  CHECK(cpu.state.PC == expected_pc);
+  CHECK(cpu.state.IME == IME_OFF);
+
+}