BAEL-3069 Spring jdbcTemplate Unit Testing

persistence-modules/spring-persistence-simple/pom.xml

@@ -92,6 +92,12 @@
             <version>${org.springframework.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId> 
+            <artifactId>mockito-core</artifactId>
+            <version>${mockito.version}</version> 
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>com.querydsl</groupId>
             <artifactId>querydsl-jpa</artifactId>
@@ -137,6 +143,7 @@
         <tomcat-dbcp.version>9.0.0.M26</tomcat-dbcp.version>
         <jta.version>1.1</jta.version>
         <querydsl.version>4.2.1</querydsl.version>
+        <mockito.version>3.3.3</mockito.version>
 
         <!-- util -->
         <guava.version>21.0</guava.version>

persistence-modules/spring-persistence-simple/src/test/java/com/baeldung/jdbc/EmployeeDAOUnitTest.java

@@ -0,0 +1,49 @@
+package com.baeldung.jdbc;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import javax.sql.DataSource;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.junit.MockitoJUnitRunner;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
+import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseType;
+import org.springframework.test.util.ReflectionTestUtils;
+
+
+@RunWith(MockitoJUnitRunner.class)
+
+public class EmployeeDAOUnitTest {
+
+    @Mock
+    JdbcTemplate jdbcTemplate;
+
+    @Test
+    public void whenMockJdbcTemplate_thenReturnCorrectEmployeeCount() {
+        EmployeeDAO employeeDAO = new EmployeeDAO();
+        ReflectionTestUtils.setField(employeeDAO, "jdbcTemplate", jdbcTemplate);
+        Mockito.when(jdbcTemplate.queryForObject("SELECT COUNT(*) FROM EMPLOYEE", Integer.class))
+            .thenReturn(4);
+        assertEquals(4, employeeDAO.getCountOfEmployees());
+
+        Mockito.when(jdbcTemplate.queryForObject(Mockito.anyString(), Mockito.eq(Integer.class)))
+            .thenReturn(3);
+        assertEquals(3, employeeDAO.getCountOfEmployees());
+    }
+
+    @Test
+    public void whenInjectInMemoryDataSource_thenReturnCorrectEmployeeCount() {
+        DataSource dataSource = new EmbeddedDatabaseBuilder().setType(EmbeddedDatabaseType.H2)
+            .addScript("classpath:jdbc/schema.sql")
+            .addScript("classpath:jdbc/test-data.sql")
+            .build();
+        EmployeeDAO employeeDAO = new EmployeeDAO();
+        employeeDAO.setDataSource(dataSource);
+        assertEquals(4, employeeDAO.getCountOfEmployees());
+    }
+
+}