Introduce framework for running basic tests for entities (#1344)

* Introduce framework for running basic tests for entities

* Add pipeline tests to CircleCI config

* Make pipeline tests more configurable and fix CircleCI config

* Add coverage dir to pipeline package

* Add basic tests for all exchange event entities

* Add tests for remaining entities

* Create separate test scripts in package.json and add new info to README

* Update db_setup.ts to revert migrations even if you are using docker

* Automatically pull the postgres image if needed

* Add comment about why NumberToBigIntTransformer is needed

packages/pipeline/test/entities/util.ts

@@ -0,0 +1,25 @@
+import * as chai from 'chai';
+import 'mocha';
+
+import { Repository } from 'typeorm';
+
+const expect = chai.expect;
+
+/**
+ * First saves the given entity to the database, then finds it and makes sure
+ * that the found entity is exactly equal to the original one. This is a bare
+ * minimum basic test to make sure that the entity type definition and our
+ * database schema are aligned and that it is possible to save and find the
+ * entity.
+ * @param repository A TypeORM repository corresponding with the type of the entity.
+ * @param entity An instance of a TypeORM entity which will be saved/retrieved from the database.
+ */
+export async function testSaveAndFindEntityAsync<T>(repository: Repository<T>, entity: T): Promise<void> {
+    // Note(albrow): We are forced to use an 'as any' hack here because
+    // TypeScript complains about stack depth when checking the types.
+    await repository.save(entity as any);
+    const gotEntity = await repository.findOneOrFail({
+        where: entity,
+    });
+    expect(gotEntity).deep.equal(entity);
+}