test(sterni/blipqn): add sanity check

This tests that a single pixel is set in the correct place and correctly
sent over UDP.

Change-Id: I617dda739262b4c6cf55c0bf99d2f3e141adece3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/13013
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI

users/sterni/blipqn/default.nix

@@ -17,6 +17,22 @@ let
       pkgs.cbqn
     ];
 
+    doCheck = true;
+    checkInputs = [
+      pkgs.netcat-openbsd
+    ];
+    checkPhase = ''
+      runHook preCheck
+      nc -lu 2323 > raw &
+      BQN ./examples.bqn localhost 2323 32 10 235
+      kill %1
+      base64 raw > received
+      diff -u received - <<EOF
+      AAAAAAAAAAAAAAAAAAAAAAAAAgAAAAAAAAAAAAAAAAAAAAAAAAAAAA==
+      EOF
+      runHook postCheck
+    '';
+
     meta.ci.targets = [ "debug" ];
     passthru.debug = drv.overrideAttrs (old: {
       CFLAGS = "-g -Werror -DFLIPDOT_DEBUG=1";