Functional Test for `builtins.storeDir` and `builtins.currentSystem`

These were under-tested. This tests the status quo and especially
previous commit of this PR better.

tests/functional/impure-eval.sh

@@ -0,0 +1,35 @@
+source common.sh
+
+export REMOTE_STORE="dummy://"
+
+simpleTest () {
+    local expr=$1; shift
+    local result=$1; shift
+    # rest, extra args
+
+    [[ "$(nix eval --impure --raw "$@" --expr "$expr")" == "$result" ]]
+}
+
+# `builtins.storeDir`
+
+## Store dir follows `store` store setting
+simpleTest 'builtins.storeDir' '/foo' --store "$REMOTE_STORE?store=/foo"
+simpleTest 'builtins.storeDir' '/bar' --store "$REMOTE_STORE?store=/bar"
+
+# `builtins.currentSystem`
+
+## `system` alone affects by default
+simpleTest 'builtins.currentSystem' 'foo' --system 'foo'
+simpleTest 'builtins.currentSystem' 'bar' --system 'bar'
+
+## `system` affects if `eval-system` is an empty string
+simpleTest 'builtins.currentSystem' 'foo' --system 'foo' --eval-system ''
+simpleTest 'builtins.currentSystem' 'bar' --system 'bar' --eval-system ''
+
+## `eval-system` alone affects
+simpleTest 'builtins.currentSystem' 'foo' --eval-system 'foo'
+simpleTest 'builtins.currentSystem' 'bar' --eval-system 'bar'
+
+## `eval-system` overrides `system`
+simpleTest 'builtins.currentSystem' 'bar' --system 'foo' --eval-system 'bar'
+simpleTest 'builtins.currentSystem' 'baz' --system 'foo' --eval-system 'baz'

tests/functional/local.mk

@@ -71,6 +71,7 @@ nix_tests = \
   build-remote-trustless-should-fail-0.sh \
   build-remote-with-mounted-ssh-ng.sh \
   nar-access.sh \
+  impure-eval.sh \
   pure-eval.sh \
   eval.sh \
   repl.sh \