react-native-mmkv/lib/createMMKV/createMockMMKV.js

⚡️ The fastest key/value storage for React Native.

/**
 * Mock MMKV instance when used in a Jest/Test environment.
 */
export function createMockMMKV(config = { id: 'mmkv.default' }) {
    const storage = new Map();
    const listeners = new Set();
    const notifyListeners = (key) => {
        listeners.forEach((listener) => {
            listener(key);
        });
    };
    return {
        id: config.id,
        get length() {
            return storage.size;
        },
        get size() {
            return this.byteSize;
        },
        get byteSize() {
            // estimate - assumes UTF8
            return JSON.stringify(storage).length;
        },
        isReadOnly: false,
        isEncrypted: false,
        clearAll: () => {
            const keysBefore = storage.keys();
            storage.clear();
            // Notify all listeners for all keys that were cleared
            for (const key of keysBefore) {
                notifyListeners(key);
            }
        },
        remove: (key) => {
            const deleted = storage.delete(key);
            if (deleted) {
                notifyListeners(key);
            }
            return deleted;
        },
        set: (key, value) => {
            if (key === '')
                throw new Error('Cannot set a value for an empty key!');
            storage.set(key, value);
            notifyListeners(key);
        },
        getString: (key) => {
            const result = storage.get(key);
            return typeof result === 'string' ? result : undefined;
        },
        getNumber: (key) => {
            const result = storage.get(key);
            return typeof result === 'number' ? result : undefined;
        },
        getBoolean: (key) => {
            const result = storage.get(key);
            return typeof result === 'boolean' ? result : undefined;
        },
        getBuffer: (key) => {
            const result = storage.get(key);
            return result instanceof ArrayBuffer ? result : undefined;
        },
        getAllKeys: () => Array.from(storage.keys()),
        contains: (key) => storage.has(key),
        recrypt: () => {
            console.warn('Encryption is not supported in mocked MMKV instances!');
        },
        encrypt: () => {
            console.warn('Encryption is not supported in mocked MMKV instances!');
        },
        decrypt: () => {
            console.warn('Encryption is not supported in mocked MMKV instances!');
        },
        trim: () => {
            // no-op
        },
        name: 'MMKV',
        dispose: () => { },
        equals: () => {
            return false;
        },
        addOnValueChangedListener: (listener) => {
            listeners.add(listener);
            return {
                remove: () => {
                    listeners.delete(listener);
                },
            };
        },
        importAllFrom: (other) => {
            const keys = other.getAllKeys();
            let imported = 0;
            for (const key of keys) {
                const data = other.getBuffer(key);
                if (data != null) {
                    storage.set(key, data);
                    imported++;
                }
            }
            return imported;
        },
    };
}