feat: add bats tests, docs (#139)

* fix(test): ensure bats file list uses xargs

* docs(readme): use yarn for testing instructions

* fix(test): ensure pipelines fail properly

* docs(alias): fix table header

---------

Signed-off-by: Ismo Vuorinen <ismo@ivuorinen.net>

package.json

@@ -10,7 +10,7 @@
     "fix:markdown": "npx markdownlint -df .",
     "lint:prettier": "npx prettier . --check",
     "fix:prettier": "npx prettier . --write",
-    "test": "echo \"Error: no test specified\" && exit 0"
+    "test": "bash test-all.sh"
   },
   "repository": {
     "type": "git",
@@ -29,6 +29,7 @@
   "devDependencies": {
     "@ivuorinen/base-configs": "^2.0.0",
     "@types/node": "^24.0.1",
+    "bats": "^1.12.0",
     "typescript": "^5.8.3"
   },
   "packageManager": "yarn@1.22.22"