Re-seeding database between tests

[robinelvin]

I am performing browser tests of my application and between each test scenario I need to reset the database. I have been doing this by calling an API mutation exposed by the backend which calls runSeeders. I have to do it this way because the test runner does not have access to the backend in order to run CLI commands.

This works for a few tests and then stops working with the backend hanging on each call to the API. When I look at the MySQL server it is connected to I can see multiple connections sitting in the Waiting for table metadata lock state.

Is this a bug or am I doing something wrong?

[robinelvin]

After reading Demystifying ‘Waiting for table metadata lock’ in mysql 5.7
I was able to trace the issue to an open transaction with one of my queries triggered by one of my tests. When I fixed my code to commit this transaction I was able to get my tests passing perfectly.

For information here is my GraphQL mutation resolver which I use to trigger a database reset between tests:

@Resolver()
export class TestsResolver {
    private _logger: LoggingService;

    private get logger(): LoggingService {
        if (this._logger === undefined) {
            this._logger = new LoggingService('TestsResolver');
        }
        return this._logger;
    }

    @Mutation((_returns) => TestsOperationResponse)
    public async seed(@Ctx() ctx: IContext): Promise<ISimpleMutationResponse> {
        this.logger.info('Seeding database');
        try {
            const { dbSession } = ctx.req.context.dataSources;
            const mySQLSession = dbSession as MySQLSession;
            const dataSource = await mySQLSession.getDataSource();
            this.logger.debug('Recreating database');
            await dataSource.synchronize(true);
            this.logger.debug('Seeding database');
            await runSeeders(dataSource);

            this.logger.info('Database reset');
            return new TestsOperationResponse(
                true,
                'Database reset successfully'
            );
        } catch (error) {
            return new TestsOperationResponse(false, error.message);
        }
    }
}