verilog: add tests

Run recommended self-tests from iverilog's CI.

Tests add about a minute to the build time on local machine
(2 -> 3 mins).

(cherry picked from commit ba886f7)

pkgs/applications/science/electronics/verilog/default.nix

@@ -1,7 +1,17 @@
 { stdenv, fetchFromGitHub, autoconf, gperf, flex, bison, readline, ncurses
 , bzip2, zlib
+# Test inputs
+, perl
 }:
 
+let
+  iverilog-test = fetchFromGitHub {
+    owner = "steveicarus";
+    repo = "ivtest";
+    rev = "6882cb8ec08926c4e356c6092f0c5f8c23328d5c";
+    sha256 = "04sj5nqzwls1y760kgnd9c2whkcrr8kvj9lisd5rvk0w580kjb2x";
+  };
+in
 stdenv.mkDerivation rec {
   pname = "iverilog";
   version = "unstable-2020-08-24";
@@ -24,6 +34,28 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ readline ncurses bzip2 zlib ];
 
+  # tests from .travis.yml
+  doCheck = true; # runs ``make check``
+  # most tests pass, but some that rely on exact text of floating-point numbers fail on aarch64.
+  doInstallCheck = !stdenv.isAarch64;
+  installCheckInputs = [ perl ];
+
+  installCheckPhase = ''
+    # copy tests to allow writing results
+    export TESTDIR=$(mktemp -d)
+    cp -r ${iverilog-test}/* $TESTDIR
+
+    pushd $TESTDIR
+
+    # Run & check tests
+    PATH=$out/bin:$PATH perl vvp_reg.pl
+    # Check the tests, will error if unexpected tests fail. Some failures MIGHT be normal.
+    diff regression_report-devel.txt regression_report.txt
+    PATH=$out/bin:$PATH perl vpi_reg.pl
+
+    popd
+  '';
+
   meta = with stdenv.lib; {
     description = "Icarus Verilog compiler";
     homepage = "http://iverilog.icarus.com/";