diff --git a/Makefile b/Makefile
index 36c590c..24c6f73 100644
--- a/Makefile
+++ b/Makefile
@@ -12,6 +12,8 @@ upload: $(TARGET).hex
 	while [ ! -r $(USB_DEVICE) ]; do sleep 1; done; \
 	avrdude -p $(MCU) -c avr109 -U flash:w:$(TARGET).hex -P $(USB_DEVICE)
 
+test: ; racket test.rkt
+
 clean:
 	-rm -f $(TARGET){,.hex} *.o *.elf *.s
 
@@ -28,3 +30,5 @@ $(TARGET).hex: $(TARGET).elf
 usb_keyboard.s: usb_keyboard.h usb_keyboard.c
 	avr-gcc -std=gnu99 -S -D F_CPU=$(F_CPU)UL -mmcu=$(MCU) -c \
 	  -o usb_keyboard.s usb_keyboard.c
+
+.PHONY: build upload test clean
diff --git a/test.rkt b/test.rkt
new file mode 100644
index 0000000..e8a267e
--- /dev/null
+++ b/test.rkt
@@ -0,0 +1,69 @@
+#lang racket
+
+(define pins (make-vector 20))
+(define keys (make-vector 44 #f))
+
+(define output void)
+(define input void)
+(define pause void)
+
+(define (high pin) (vector-set! pins pin #t))
+(define (low pin) (vector-set! pins pin #f))
+
+(define (for-each-vector f v) (for ([x v]) (f x)))
+
+(define last-usb-frame #f)
+
+(define (call-c-func f-name . args)
+  ;; (printf "FFI ~s~n" args)
+  (set! last-usb-frame args))
+
+(define (active-row)
+  (for/first ([pin row-pins]
+              [row (range (length rows))]
+              #:when (not (vector-ref pins pin)))
+    row))
+
+(define (col-for pin)
+  (for/first ([c-pin column-pins]
+              [col (range (length columns))]
+              #:when (= c-pin pin))
+    col))
+
+(define (low? pin)
+  ;; (when (vector-ref keys (offset-for (active-row) (col-for pin)))
+  ;;     (printf "lookup ~s ~s ~n" pin (offset-for (active-row) (col-for pin)))
+  ;;     (printf "Keys ~s~n" keys))
+  (vector-ref keys (offset-for (active-row) (col-for pin))))
+
+(define (make-test-data)
+  ;; have to put this in a function so we can internal-define; eww
+  (include "keycodes.scm")
+  ;; pair of pins/keycodes
+  `(((1) . (0 ,key-w 0 0 0 0 0))
+    ((2) . (0 ,key-e 0 0 0 0 0))))
+
+(define test-data (make-test-data))
+
+(define failures 0)
+
+(define (fail expected actual)
+  (set! failures (add1 failures))
+  (printf "Expected ~s, got ~s~n" expected actual))
+
+;; we can perform our checks here and make changes to the pin state.
+(define-syntax free!
+  (syntax-rules ()
+    [(free! body) (if (empty? test-data)
+                      (exit (if (= 0 failures) 0 1))
+                      (let ([test-case (car test-data)])
+                        (for ([i (vector-length keys)])
+                          (vector-set! keys i
+                                       (and (member i (car test-case)) #t)))
+                        body
+                        (if (equal? (cdr test-case) last-usb-frame)
+                            (printf ".~n")
+                            (fail (cdr test-case) last-usb-frame))
+                        (set! test-data (cdr test-data))))]))
+
+(include "menelaus.scm")