NixExprs: extract the escape function and test it

t/Helper/escape.t

@@ -0,0 +1,25 @@
+use strict;
+use Setup;
+use Data::Dumper;
+use Test2::V0;
+use Hydra::Helper::Escape;
+
+subtest "checking individual attribute set elements" => sub {
+    my %values = (
+        "" => '""',
+        "." => '"."',
+        "foobar" => '"foobar"',
+        "foo.bar" => '"foo.bar"',
+        "🌮" => '"🌮"',
+        'foo"bar' => '"foo\"bar"',
+        'foo\\bar' => '"foo\\\\bar"',
+        '$bar' => '"\\$bar"',
+    );
+
+    for my $input (keys %values) {
+        my $value = $values{$input};
+        is(escapeString($input), $value, "Escaping the value: " . $input);
+    }
+};
+
+done_testing;