@isTest
public class NotifyBatchTest {
    @isTest
    static void testNotifyBatch() {
        // Create test data for ProcessInstance records
        List<ProcessInstance> testProcessInstances = new List<ProcessInstance>();
        for (Integer i = 0; i < 200; i++) { // Creating more than 100 records to test batch size
            ProcessInstance pi = new ProcessInstance(Status = 'Pending');
            testProcessInstances.add(pi);
        }
        insert testProcessInstances;

        Test.startTest();

        // Schedule the batch class
        String jobId = System.schedule('Test NotifyBatch', '0 0 0 15 3 ? 2022', new NotifyBatch());

        Test.stopTest();

        // Verify that the batch job has processed the records
        // You can add your own assertions here based on your batch logic

        // Query ProcessInstanceWorkitem records or assert other expected behavior

        // Example: Query ProcessInstanceWorkitem records
        List<ProcessInstanceWorkitem> workitems = [
            SELECT Id
            FROM ProcessInstanceWorkitem
            WHERE ProcessInstanceId IN :testProcessInstances
        ];

        // Add your assertions here to verify the expected behavior of the batch job
        System.assertEquals(testProcessInstances.size(), workitems.size());

        // Clean up the test data
        delete testProcessInstances;

        // Optionally, you can assert other aspects of the batch job's behavior
        // For example, you can check the contents of the email messages sent, etc.
    }
}