Fix CALL and add test

src/cpu/instruction.rs

@@ -545,6 +545,7 @@ impl<'a> RunView<'a, InstructionExecutionState> {
                 self.push_byte(low_byte(pc))
             }
             M7 => self.execute_m1(),
+            _ => unreachable!(),
         }
     }
 

src/cpu/mod.rs

@@ -317,6 +317,7 @@ enum MCycle {
     M5,
     M6,
     M7,
+    M8,
 }
 
 impl MCycle {
@@ -327,7 +328,8 @@ impl MCycle {
             M4 => M5,
             M5 => M6,
             M6 => M7,
-            M7 => unreachable!(),
+            M7 => M8,
+            M8 => unreachable!(),
         }
     }
 }

src/cpu/tests/branch.rs

@@ -275,6 +275,14 @@ fn call_bus_activity() {
     assert_eq!(bench.trace, bench.expected)
 }
 
+#[test]
+fn ret_after_call() {
+    let mut bench = TestBench::default();
+    bench.trace_call(0x1234);
+    bench.trace_ret(0x5678);
+    assert_eq!(bench.trace, bench.expected)
+}
+
 impl TestBench {
     fn trace_call(&mut self, target: u16) {
         let sp = self.cpu.data.sp;