From 9c2d96ccd73da271f99c148c429505d1def46000 Mon Sep 17 00:00:00 2001
From: shapirov103 <shapirov@amazon.com>
Date: Sat, 27 Jun 2020 13:13:28 -0400
Subject: [PATCH 1/2] Loading JDBC driver unit test

---
 .../jdbc/JdbcDriverLoadingUnitTest.java       | 72 +++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 persistence-modules/core-java-persistence/src/test/java/com/baeldung/jdbc/JdbcDriverLoadingUnitTest.java

diff --git a/persistence-modules/core-java-persistence/src/test/java/com/baeldung/jdbc/JdbcDriverLoadingUnitTest.java b/persistence-modules/core-java-persistence/src/test/java/com/baeldung/jdbc/JdbcDriverLoadingUnitTest.java
new file mode 100644
index 0000000000..77b6bef4eb
--- /dev/null
+++ b/persistence-modules/core-java-persistence/src/test/java/com/baeldung/jdbc/JdbcDriverLoadingUnitTest.java
@@ -0,0 +1,72 @@
+package com.baeldung.jdbc;
+
+import static org.junit.Assert.*;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.sql.Driver;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+
+public class JdbcDriverLoadingUnitTest {
+
+    @Before
+    public void setup() throws SQLException {
+        if(!org.postgresql.Driver.isRegistered()) {
+            org.postgresql.Driver.register();
+        }
+    }
+    /**
+     * Driver is registered automatically with the service provider mechanism.
+     */
+    @Test
+    public void givenJdbcDriverWithSP_whenGettingDriver_thenDriverIsReturned() throws SQLException {
+        Driver driver = getDriver();
+        assertNotNull("Expected initialized postgres driver", driver);
+    }
+
+    /**
+     * Driver is registered automatically, then deregistered.
+     * @throws SQLException
+     */
+    @Test(expected = SQLException.class)
+    public void givenRegisteredJdbcDriver_whenDeregister_thenNoDriverIsReturned() throws SQLException {
+        Driver driver = getDriver();
+        DriverManager.deregisterDriver(driver);
+        driver = getDriver();
+        assertNull(driver);
+    }
+
+    /**
+     * Driver is automatically by the JVM, then deregistered, then registered again.
+     * @throws SQLException
+     * @throws ClassNotFoundException
+     */
+    @Test
+    public void givenNoRegisteredDriver_whenClassForName_thenDriverIsReturned() throws SQLException, ClassNotFoundException {
+        deregisterDriver();
+
+        Driver driver = null;
+        try {
+            driver = getDriver();
+        }
+        catch (SQLException e) {
+            // expected
+        }
+        assertNull("Must fail on attempt to get a deregistered driver", driver);
+
+        org.postgresql.Driver.register(); // This is invoked as part of Class.forName() logic
+
+        driver  = getDriver();
+        assertNotNull("Driver must register as part of class loading", driver);
+    }
+
+    private void deregisterDriver() throws SQLException {
+        org.postgresql.Driver.deregister();
+    }
+
+    private Driver getDriver() throws SQLException {
+        return DriverManager.getDriver("jdbc:postgresql:");
+    }
+}

From 16171e95d35688b3ea959f09e5cdf856e3424dc0 Mon Sep 17 00:00:00 2001
From: shapirov103 <shapirov@amazon.com>
Date: Thu, 2 Jul 2020 23:40:28 -0400
Subject: [PATCH 2/2] addressing code review comments

---
 .../java/com/baeldung/jdbc/JdbcDriverLoadingUnitTest.java     | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/persistence-modules/core-java-persistence/src/test/java/com/baeldung/jdbc/JdbcDriverLoadingUnitTest.java b/persistence-modules/core-java-persistence/src/test/java/com/baeldung/jdbc/JdbcDriverLoadingUnitTest.java
index 77b6bef4eb..387c050285 100644
--- a/persistence-modules/core-java-persistence/src/test/java/com/baeldung/jdbc/JdbcDriverLoadingUnitTest.java
+++ b/persistence-modules/core-java-persistence/src/test/java/com/baeldung/jdbc/JdbcDriverLoadingUnitTest.java
@@ -13,7 +13,7 @@ public class JdbcDriverLoadingUnitTest {
 
     @Before
     public void setup() throws SQLException {
-        if(!org.postgresql.Driver.isRegistered()) {
+        if (!org.postgresql.Driver.isRegistered()) {
             org.postgresql.Driver.register();
         }
     }
@@ -58,7 +58,7 @@ public class JdbcDriverLoadingUnitTest {
 
         org.postgresql.Driver.register(); // This is invoked as part of Class.forName() logic
 
-        driver  = getDriver();
+        driver = getDriver();
         assertNotNull("Driver must register as part of class loading", driver);
     }