Check schema migration is reversable

Author: foriequal0

.travis.yml

@@ -19,6 +19,14 @@ jobs:
         - yarn run lint
         - NODE_ENV=test yarn migrate
         - yarn run test
+    - name: Check schema migration is reversable
+      before_install:
+        - npm install -g yarn
+        - yarn install
+      before_script:
+        - psql postgres -f create_user_and_db.sql
+      script:
+        - ./check-schema-migration-reversable.sh
 services:
   - docker
   - postgresql

check-schema-migration-reversable.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+set -ex;
+
+export NODE_ENV="test"
+DATABASE="codechain-indexer-test"
+
+function mktemp2 {
+	PREFIX="$1"
+	POSTFIX="$2"
+	python -c "import tempfile; print(tempfile.NamedTemporaryFile(prefix='$PREFIX', suffix='$SUFFIX', delete=False).name)"
+}
+BEFORE=$(mktemp2 "${DATABASE}." ".schema.before.sql")
+AFTER=$(mktemp2 "${DATABASE}." ".schema.after.sql")
+
+LAST_BEFORE=$(perl -e 'my @files=`ls src/migrations`; print @files[-2]')
+if [[ "${LAST_BEFORE}" = "" ]]; then 
+    echo "$0: Can't find a migration file before the last one, exiting..."
+    exit 1;
+fi
+
+yarn sequelize db:migrate --to "${LAST_BEFORE}"
+
+pg_dump -s "${DATABASE}" > "${BEFORE}"
+
+yarn sequelize db:migrate
+yarn sequelize db:migrate:undo
+
+pg_dump -s "${DATABASE}" > "${AFTER}"
+
+diff "${BEFORE}" "${AFTER}"