@IsTest
public class Object_1TriggerTest {
    @IsTest
    public static void Load_field_1_from_metadata(){
        //Initialization and data loading
        Object_1__c instance_of_object_1 = new Object_1__c(
            Name = 'Test',
            Picklist_1__c = 'picklist value 1'
        );

        MockMetadataUtils.insert_custom_metadata_mock();

        //Test
        Test.startTest();
        insert instance_of_object_1;
        Test.stopTest();
        //ASSERTS
        instance_of_object_1 = [
            SELECT ID,Field_1__c 
            FROM Object_1__c 
            WHERE ID = :instance_of_object_1.Id
        ];
        System.assertEquals('Value of metadata', instance_of_object_1.Field_1__c);
    }
}

@IsTest
public class Object_1TriggerTest {
    @IsTest
    public static void Load_field_1_from_metadata(){
        //Initialization and data loading
        Object_1__c instance_of_object_1 = new Object_1__c(
            Name = 'Test',
            Picklist_1__c = 'picklist value 1'
        );

        MockMetadataUtils.insert_custom_metadata_mock();

        //Test
        Test.startTest();
        insert instance_of_object_1;
        Test.stopTest();
        //ASSERTS
        instance_of_object_1 = [
            SELECT ID,Field_1__c 
            FROM Object_1__c 
            WHERE ID = :instance_of_object_1.Id
        ];
        System.assertEquals('Value of metadata', instance_of_object_1.Field_1__c);
    }
}

public class MockMetadataUtils {
    
    public static List<example_metadata__mdt> rollupsumary = new List<example_metadata__mdt>();

    public static void insert_custom_metadata_mock(){
        example_metadata__mdt rollupsumary = new example_metadata__mdt();
        Map<String,Object> fields = (Map<String, Object>) 
            JSON.deserializeUntyped(JSON.serializePretty(rollupsumary));
        fields.put(
            example_metadata__mdt.Field_1__c.getDescribe().getName(),
            'picklist value 1'
        );
        fields.put(
            example_metadata__mdt.Field_2__c.getDescribe().getName(),
            'Value of metadata'
        );
        rollupsumary = (example_metadata__mdt) 
            JSON.deserialize(JSON.serialize(fields), example_metadata__mdt.class);
        MockMetadataUtils.rollupsumary.add(rollupsumary);
    }
}

public class MockMetadataUtils {
    
    public static List<example_metadata__mdt> rollupsumary = new List<example_metadata__mdt>();

    public static void insert_custom_metadata_mock(){
        example_metadata__mdt rollupsumary = new example_metadata__mdt();
        Map<String,Object> fields = (Map<String, Object>) 
            JSON.deserializeUntyped(JSON.serializePretty(rollupsumary));
        fields.put(
            example_metadata__mdt.Field_1__c.getDescribe().getName(),
            'picklist value 1'
        );
        fields.put(
            example_metadata__mdt.Field_2__c.getDescribe().getName(),
            'Value of metadata'
        );
        rollupsumary = (example_metadata__mdt) 
            JSON.deserialize(JSON.serialize(fields), example_metadata__mdt.class);
        MockMetadataUtils.rollupsumary.add(rollupsumary);
    }
}

public class Object_1TriggerHelper {
    public static void updateSomeField(List<Object_1__c> test_Objects){
        List<example_metadata__mdt> custom_metadata_records;
        Map<String,example_metadata__mdt> custom_metadata_records_map = new Map<String,example_metadata__mdt>();
        
        if(Test.isRunningTest()){
            custom_metadata_records = MockMetadataUtils.rollupsumary;
        }else{
            custom_metadata_records = example_metadata__mdt.getAll().values();
        }

        for(example_metadata__mdt custom_metadata : custom_metadata_records){
            custom_metadata_records_map.put(custom_metadata.Field_1__c, custom_metadata);
        }

        for(Object_1__c test_Object :test_Objects){
            test_Object.Field_1__c = custom_metadata_records_map.get(test_Object.Picklist_1__c) != null ? 
                custom_metadata_records_map.get(test_Object.Picklist_1__c).Field_2__c :
                null;
        }
    }
}

public class Object_1TriggerHelper {
    public static void updateSomeField(List<Object_1__c> test_Objects){
        List<example_metadata__mdt> custom_metadata_records;
        Map<String,example_metadata__mdt> custom_metadata_records_map = new Map<String,example_metadata__mdt>();
        
        if(Test.isRunningTest()){
            custom_metadata_records = MockMetadataUtils.rollupsumary;
        }else{
            custom_metadata_records = example_metadata__mdt.getAll().values();
        }

        for(example_metadata__mdt custom_metadata : custom_metadata_records){
            custom_metadata_records_map.put(custom_metadata.Field_1__c, custom_metadata);
        }

        for(Object_1__c test_Object :test_Objects){
            test_Object.Field_1__c = custom_metadata_records_map.get(test_Object.Picklist_1__c) != null ? 
                custom_metadata_records_map.get(test_Object.Picklist_1__c).Field_2__c :
                null;
        }
    }
}