diff --git a/src/DataParserPluginBase.php b/src/DataParserPluginBase.php
index c74c6c53acbefb03f4812335145229d00fc3cead..692942b00c39a853dd003964859738b21b56b1db 100644
--- a/src/DataParserPluginBase.php
+++ b/src/DataParserPluginBase.php
@@ -149,6 +149,10 @@ abstract class DataParserPluginBase extends PluginBase implements DataParserPlug
    *   TRUE if a valid source URL was opened
    */
   protected function nextSource() {
+    if (empty($this->urls)) {
+      return FALSE;
+    }
+
     while ($this->activeUrl === NULL || (count($this->urls) - 1) > $this->activeUrl) {
       if (is_null($this->activeUrl)) {
         $this->activeUrl = 0;
diff --git a/tests/src/Unit/DataParserPluginBaseTest.php b/tests/src/Unit/DataParserPluginBaseTest.php
new file mode 100644
index 0000000000000000000000000000000000000000..5e32deee36b0b4facd17de6bf98640ee85bb0eaa
--- /dev/null
+++ b/tests/src/Unit/DataParserPluginBaseTest.php
@@ -0,0 +1,97 @@
+<?php
+
+namespace Drupal\Tests\migrate_plus\Unit;
+
+use Drupal\migrate_plus\DataParserPluginBase;
+use Drupal\Tests\migrate\Unit\MigrateTestCase;
+
+/**
+ * @coversDefaultClass \Drupal\migrate_plus\DataParserPluginBase
+ *
+ * @group migrate_plus
+ */
+class DataParserPluginBaseTest extends MigrateTestCase {
+
+  /**
+   * @covers ::nextSource
+   */
+  public function testNextSourceWithOneUrl() {
+    $parser = $this->getMockedDataParser();
+    $parser->expects($this->once())
+      ->method('openSourceUrl')
+      ->willReturn(TRUE);
+    $this->assertTrue($parser->nextSource());
+  }
+
+  /**
+   * @covers ::nextSource
+   */
+  public function testNextSourceWithoutUrls() {
+    $config = [
+      'urls' => [],
+    ];
+
+    $parser = $this->getMockedDataParser($config);
+    $parser->expects($this->never())
+      ->method('openSourceUrl');
+    $this->assertFalse($parser->nextSource());
+  }
+
+  /**
+   * @covers ::count
+   */
+  public function testCountWithoutUrls() {
+    $config = [
+      'urls' => [],
+    ];
+
+    $parser = $this->getMockedDataParser($config);
+    $parser->expects($this->never())
+      ->method('openSourceUrl');
+    $this->assertEquals(0, $parser->count());
+  }
+
+  /**
+   * Returns a mocked data parser.
+   *
+   * @param array $configuration
+   *   The configuration to pass to the data parser.
+   *
+   * @return \PHPUnit\Framework\MockObject\MockObject|\Drupal\Tests\migrate_plus\Unit\DataParserPluginBaseMock
+   *   An mock instance of DataParserPluginBase.
+   */
+  protected function getMockedDataParser(array $configuration = []) {
+    // Set constructor arguments.
+    $configuration += [
+      'urls' => ['http://example.org/data_parser_test'],
+      'item_selector' => 0,
+    ];
+    $plugin_id = 'foo';
+    $plugin_definition = [
+      'id' => 'foo',
+      'title' => 'Foo',
+    ];
+
+    return $this->getMockBuilder(DataParserPluginBaseMock::class)
+      ->setConstructorArgs([$configuration, $plugin_id, $plugin_definition])
+      ->setMethods(['openSourceUrl'])
+      ->getMockForAbstractClass();
+  }
+
+}
+
+/**
+ * Mock for abstract class DataParserPluginBase.
+ *
+ * This mock is used to make certain methods publicly accessible.
+ */
+abstract class DataParserPluginBaseMock extends DataParserPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function nextSource() {
+    return parent::nextSource();
+  }
+
+}