improve: evaluate integration tests in parallel

shell.nix

@@ -1,6 +1,11 @@
 {
   pkgs ? import (import ./mach_nix/nix/nixpkgs-src.nix) { config = {}; },
-  pypiData,
+  pypiData ? (import ./mach_nix/nix/deps-db-and-fetcher.nix {
+    inherit pkgs;
+  }).pypi_deps_db_src,
+  chondaChannelsJson ? import ./mach_nix/nix/conda-channels.nix {
+    providers = { _default = [ "conda/main" "conda/r" "conda/conda-forge"]; };
+  },
   ...
 }:
 with pkgs;
@@ -12,10 +17,12 @@ mkShell {
   buildInputs = [
     (python.withPackages ( ps: with ps; machnixDeps ++ [ pytest_6 pytest-xdist twine ] ))
     nix-prefetch-git
+    pkgs.parallel
   ];
   shellHook = ''
     export PYTHONPATH=$(pwd)/
     export PYPI_DATA=${pypiData}
+    export CONDA_DATA=${chondaChannelsJson.condaChannelsJson}
     git config core.hooksPath ./git-hooks
   '';
 }

tests/execute.sh

@@ -1,3 +1,3 @@
 #!/usr/bin/env bash
 
-nix-build all-tests.nix --no-out-link --show-trace $@
+ls ./test_* | parallel -a - -j 10 --halt now,fail=1 nix-build --show-trace