Add tests

app.json

@@ -1,5 +1,10 @@
 {
   "name": "Start on Heroku: Java",
   "description": "A barebones Java app, which can easily be deployed to Heroku.",
-  "addons": ["heroku-postgresql"]
+  "addons": ["heroku-postgresql"],
+  "environments": {
+    "test": {
+      "addons": ["heroku-postgresql:in-dyno"]
+    }
+  }
 }

pom.xml

@@ -41,6 +41,16 @@
             <groupId>org.postgresql</groupId>
             <artifactId>postgresql</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-webmvc-test</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>

src/test/java/com/heroku/java/GettingStartedApplicationTest.java

@@ -0,0 +1,62 @@
+package com.heroku.java;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.webmvc.test.autoconfigure.WebMvcTest;
+import org.springframework.test.context.bean.override.mockito.MockitoBean;
+import org.springframework.test.web.servlet.MockMvc;
+
+import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.ResultSet;
+import java.sql.Statement;
+import java.sql.Timestamp;
+import java.time.Instant;
+
+import static org.mockito.Mockito.when;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
+
+@WebMvcTest(GettingStartedApplication.class)
+class GettingStartedApplicationTest {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @MockitoBean
+    private DataSource dataSource;
+
+    @Test
+    void indexReturnsOk() throws Exception {
+        mockMvc.perform(get("/"))
+                .andExpect(status().isOk())
+                .andExpect(view().name("index"));
+    }
+
+    @Test
+    void databaseReturnsRecords() throws Exception {
+        Connection connection = org.mockito.Mockito.mock(Connection.class);
+        Statement statement = org.mockito.Mockito.mock(Statement.class);
+        ResultSet resultSet = org.mockito.Mockito.mock(ResultSet.class);
+
+        when(dataSource.getConnection()).thenReturn(connection);
+        when(connection.createStatement()).thenReturn(statement);
+        when(statement.executeQuery("SELECT tick FROM ticks")).thenReturn(resultSet);
+        when(resultSet.next()).thenReturn(true, false);
+        when(resultSet.getTimestamp("tick")).thenReturn(Timestamp.from(Instant.parse("2024-01-01T00:00:00Z")));
+
+        mockMvc.perform(get("/database"))
+                .andExpect(status().isOk())
+                .andExpect(view().name("database"))
+                .andExpect(model().attributeExists("records"));
+    }
+
+    @Test
+    void databaseReturnsErrorOnFailure() throws Exception {
+        when(dataSource.getConnection()).thenThrow(new RuntimeException("Connection refused"));
+
+        mockMvc.perform(get("/database"))
+                .andExpect(view().name("error"))
+                .andExpect(model().attribute("message", "Connection refused"));
+    }
+}