feat: add tests for commands examples

tests/extra/commands.examples.nix

@@ -0,0 +1,52 @@
+{ pkgs, devshell, runTest }:
+{
+  nested =
+    let
+      shell = devshell.mkShell {
+        devshell.name = "nested-commands-test";
+        commands = (import ../../nix/commands/examples.nix { inherit pkgs; }).nested;
+      };
+    in
+    runTest "nested" { } ''
+      # Load the devshell
+      source ${shell}/env.bash
+
+      type -p python3
+
+      # Has hyperfine
+      # Has no yq
+      if [[ -z "$(type -p hyperfine)" ]]; then
+        echo "OK"
+      else
+        echo "Error! Has hyperfine"
+      fi
+
+      # Has no yq
+      if [[ -z "$(type -p yq)" ]]; then
+        echo "OK"
+      else
+        echo "Error! Has yq"
+      fi
+    '';
+
+  flat =
+    let
+      shell = devshell.mkShell {
+        devshell.name = "flat-commands-test";
+        commands = (import ../../nix/commands/examples.nix { inherit pkgs; }).flat;
+      };
+    in
+    runTest "flat" { } ''
+      # Load the devshell
+      source ${shell}/env.bash
+
+      # Has yarn
+      type -p yarn
+
+      # Has hello
+      type -p hello
+
+      # Has black
+      type -p black
+    '';
+}