[FIXED] How to mock Spring's JdbcTemplate.queryForList using Mockito?

Issue

I want to know how to mock the particular code using Mockito:

List<Map<String, Object>> list = jdbcTemplate.queryForList(
    sqlQuery, 
    new Object[] { inflowId }
);

I tried the following code:

Mockito.doReturn(list)
       .when(jdbcTemplate)
       .queryForList(Mockito.anyString(), Mockito.any(Class.class));

and:

when(
    jdbcTemplate.queryForList(Mockito.anyString(), Mockito.any(Object[].class))
).thenReturn(list);

My problem is that particular method is not getting mocked in JUnit. When the method is called, it returns null whereas it should return the list.

Solution

This should work:

import org.hamcrest.CoreMatchers;
import org.junit.Assert;
import org.junit.Test;
import org.mockito.ArgumentMatchers;
import org.mockito.Mockito;
import org.springframework.jdbc.core.JdbcTemplate;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

public class DemoTest {

    @Test
    public void mockJdbcTemplate() {
        JdbcTemplate mockTemplate = Mockito.mock(JdbcTemplate.class);

        List<Map<String, Object>> mockResult = new ArrayList<>();

        Mockito.when(mockTemplate.queryForList(Mockito.anyString(), ArgumentMatchers.<Object>any())).thenReturn(mockResult);
        // Alternatively:
        // when(mockTemplate.queryForList(anyString(), Mockito.<Object>any())).thenReturn(mockResult);

        String query = "some query";
        Object[] params = new Object[]{1};

        List<Map<String, Object>> returnedResult = mockTemplate.queryForList(query, params);

        Assert.assertThat(returnedResult, CoreMatchers.sameInstance(mockResult));
    }

}

The trick is to use ArgumentMatchers.<Object>any() as there are multiple queryForList method implementations and the one we want to mock receives a varargs parameter.

Answered By - Behrang
Answer Checked By - David Goodson (JavaFixing Volunteer)