MNT Add more robust tests

.gitattributes

@@ -2,3 +2,4 @@
 /docs export-ignore
 /.gitattributes export-ignore
 /.gitignore export-ignore
+/.github export-ignore

tests/DynamoDbSessionTest.php

@@ -2,15 +2,54 @@
 
 namespace SilverStripe\DynamoDb\Tests;
 
+use ReflectionProperty;
+use SilverStripe\Core\Environment;
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\DynamoDb\Model\DynamoDbSession;
 
 class DynamoDbSessionTest extends SapphireTest
 {
-
     public function testGetReturnsNullWhenNotConfigured()
     {
+        // Ensure the session table is null for this test
+        $origTableName = Environment::getEnv('AWS_DYNAMODB_SESSION_TABLE');
+        Environment::setEnv('AWS_DYNAMODB_SESSION_TABLE', null);
+
         $this->assertNull(DynamoDbSession::get());
+
+        Environment::setEnv('AWS_DYNAMODB_SESSION_TABLE', $origTableName);
+    }
+
+    public function testGetReturnsSessionWhenConfigured()
+    {
+        // Ensure the session table is not null for this test
+        $origTableName = Environment::getEnv('AWS_DYNAMODB_SESSION_TABLE');
+        $origRegionName = Environment::getEnv('AWS_REGION_NAME');
+        $origDynamoDBEndpoint = Environment::getEnv('AWS_DYNAMODB_ENDPOINT');
+        $origAccessKey = Environment::getEnv('AWS_ACCESS_KEY');
+        $origSecretKey = Environment::getEnv('AWS_SECRET_KEY');
+        Environment::setEnv('AWS_DYNAMODB_SESSION_TABLE', 'sessiontable');
+        Environment::setEnv('AWS_REGION_NAME', 'ap-southeast-2');
+        Environment::setEnv('AWS_DYNAMODB_ENDPOINT', 'http://www.example.com/');
+        Environment::setEnv('AWS_ACCESS_KEY', 'arbitrary-value');
+        Environment::setEnv('AWS_SECRET_KEY', 'arbitrary-value');
+        $session = DynamoDbSession::get();
+
+        // Check there is a session
+        $this->assertInstanceOf(DynamoDbSession::class, $session);
+
+        $reflectionTable = new ReflectionProperty($session, 'table');
+        $reflectionTable->setAccessible(true);
+
+        // Check the session set the correct table name
+        $this->assertSame('sessiontable', $reflectionTable->getValue($session));
+
+        // Set env vars back to whatever they were before
+        Environment::setEnv('AWS_DYNAMODB_SESSION_TABLE', $origTableName);
+        Environment::setEnv('AWS_REGION_NAME', $origRegionName);
+        Environment::setEnv('AWS_DYNAMODB_ENDPOINT', $origDynamoDBEndpoint);
+        Environment::setEnv('AWS_ACCESS_KEY', $origAccessKey);
+        Environment::setEnv('AWS_SECRET_KEY', $origSecretKey);
     }
 
     public function testGetSessionHandler()