improve test scripts

* validated with shellcheck
* allow to evaluate just one for convenience
* reduce verbosity and improve debugging output

tests/eval-one.sh

@@ -0,0 +1,35 @@
+#!/bin/sh
+set -u
+here=$(cd "$(dirname "$0")" && pwd)
+
+if [ -z "$1" ]; then
+  echo "Usage: $0 <profile>"
+  exit 1
+fi
+
+profile=$1
+logfile=$(mktemp)
+
+# shellcheck disable=SC2039
+echo -n "evaluating $profile: "
+
+nix-build \
+  '<nixpkgs/nixos>' \
+  -I "nixos-config=$here/eval-test.nix" \
+  -I "nixos-hardware-profile=$profile" \
+  --dry-run \
+  --no-out-link \
+  --show-trace \
+  -A system > "$logfile" 2>&1
+ret=$?
+
+if [ "$ret" -gt 0 ]; then
+  echo ERROR
+  echo ===================================================================== >&2
+  cat "$logfile" >&2
+else
+  echo OK
+fi
+
+rm "$logfile"
+exit "$ret"

tests/eval-test.sh

@@ -1,15 +1,11 @@
 #!/bin/sh
+set -efu
+cd "$(dirname "$0")/.." || exit 1
 
-set -e
-
-cd "$(dirname "$0")/.."
+echo "### Evaluating all profiles ###"
+echo
 
+# shellcheck disable=SC2044
 for profile in $(find . -name default.nix); do
-  echo evaluating $profile >&2
-
-  nix-build '<nixpkgs/nixos>' \
-    -I nixos-config=tests/eval-test.nix \
-    -I nixos-hardware-profile=$profile \
-    -A system \
-    --dry-run
+  ./tests/eval-one.sh "$profile"
 done