带有 expo sqlite 调用的单元测试类开玩笑

Question

Having trouble learning to unit test my expo/react-native app. How would I unit test adding transactions to the store in this class:

export default class TransactionsStore {
    @observable _transactions = [];

    constructor(rootStore) {
        this.rootStore = rootStore;
    }

    @action addTransaction(t, db) {
        db.transaction(tx => {
            tx.executeSql(
                'INSERT INTO transactions (categoryId, description, date, amount, currencyCode, isReported) VALUES (?,?,?,?,?,?);',
                [t.category, t.description, t.date, t.amount, t.currency.code, t.report],
                (tx, result) => { t.id = result.insertId; }
            );
        }, error => alert(error));
        this.reloadTransactions(db);
    }
}

All the callbacks within callbacks make this very difficult. I guess I have to mock db.transaction somehow but I can't see how to do it in such a way to give a fake (tx, result) into that nested function of executeSql .

Answer 1

Was able to get this working with some thought:

var sqlResult = { insertId: 1, rows: { _array: [] } };
const tx = { executeSql: jest.fn((query, sub=[], func=()=>true) => func({}, sqlResult)) };
const db = { transaction: jest.fn((func) => func(tx)) };
const rootStore = { db: db } };

describe('TransactionsStore', () => {
    const store = new TransactionsStore(rootStore);

    it('mocks sql', () => {
        expect(tx.executeSql.mock.calls.length).toBeGreaterThan(0);
    });
});

Talk about a brain workout! This way I can manipulate sqlResult in between tests to fake some data from the sql calls