diff --git a/src/ConvertKit_API.php b/src/ConvertKit_API.php
index a2a0b0b..fa06d23 100644
--- a/src/ConvertKit_API.php
+++ b/src/ConvertKit_API.php
@@ -933,6 +933,155 @@ public function get_resources(string $resource)
         return $_resource;
     }
 
+    /**
+     * Get subscribers.
+     *
+     * @param string    $subscriber_state Subscriber State (active|bounced|cancelled|complained|inactive).
+     * @param string    $email_address    Search susbcribers by email address. This is an exact match search.
+     * @param \DateTime $created_after    Filter subscribers who have been created after this date.
+     * @param \DateTime $created_before   Filter subscribers who have been created before this date.
+     * @param \DateTime $updated_after    Filter subscribers who have been updated after this date.
+     * @param \DateTime $updated_before   Filter subscribers who have been updated before this date.
+     * @param string    $sort_field       Sort Field (id|updated_at|cancelled_at).
+     * @param string    $sort_order       Sort Order (asc|desc).
+     * @param string    $after_cursor     Return results after the given pagination cursor.
+     * @param string    $before_cursor    Return results before the given pagination cursor.
+     * @param integer   $per_page         Number of results to return.
+     *
+     * @since 2.0.0
+     *
+     * @see https://developers.convertkit.com/v4.html#list-subscribers
+     *
+     * @return false|mixed
+     */
+    public function get_subscribers(
+        string $subscriber_state = 'active',
+        string $email_address = '',
+        \DateTime $created_after = null,
+        \DateTime $created_before = null,
+        \DateTime $updated_after = null,
+        \DateTime $updated_before = null,
+        string $sort_field = 'id',
+        string $sort_order = 'desc',
+        string $after_cursor = '',
+        string $before_cursor = '',
+        int $per_page = 100
+    ) {
+        // Build parameters.
+        $options = [];
+
+        if (!empty($subscriber_state)) {
+            $options['status'] = $subscriber_state;
+        }
+        if (!empty($email_address)) {
+            $options['email_address'] = $email_address;
+        }
+        if (!is_null($created_after)) {
+            $options['created_after'] = $created_after->format('Y-m-d');
+        }
+        if (!is_null($created_before)) {
+            $options['created_before'] = $created_before->format('Y-m-d');
+        }
+        if (!is_null($updated_after)) {
+            $options['updated_after'] = $updated_after->format('Y-m-d');
+        }
+        if (!is_null($updated_before)) {
+            $options['updated_before'] = $updated_before->format('Y-m-d');
+        }
+        if (!empty($sort_field)) {
+            $options['sort_field'] = $sort_field;
+        }
+        if (!empty($sort_order)) {
+            $options['sort_order'] = $sort_order;
+        }
+
+        // Build pagination parameters.
+        $options = $this->build_pagination_params(
+            params: $options,
+            after_cursor: $after_cursor,
+            before_cursor: $before_cursor,
+            per_page: $per_page
+        );
+
+        // Send request.
+        return $this->get(
+            endpoint: 'subscribers',
+            args: $options
+        );
+    }
+
+    /**
+     * Create a subscriber.
+     *
+     * Behaves as an upsert. If a subscriber with the provided email address does not exist,
+     * it creates one with the specified first name and state. If a subscriber with the provided
+     * email address already exists, it updates the first name.
+     *
+     * @param string                $email_address    Email Address.
+     * @param string                $first_name       First Name.
+     * @param string                $subscriber_state Subscriber State (active|bounced|cancelled|complained|inactive).
+     * @param array<string, string> $fields           Custom Fields.
+     *
+     * @since 2.0.0
+     *
+     * @see https://developers.convertkit.com/v4.html#create-a-subscriber
+     *
+     * @return mixed
+     */
+    public function create_subscriber(
+        string $email_address,
+        string $first_name = '',
+        string $subscriber_state = '',
+        array $fields = []
+    ) {
+        // Build parameters.
+        $options = ['email_address' => $email_address];
+
+        if (!empty($first_name)) {
+            $options['first_name'] = $first_name;
+        }
+        if (!empty($subscriber_state)) {
+            $options['state'] = $subscriber_state;
+        }
+        if (count($fields)) {
+            $options['fields'] = $fields;
+        }
+
+        // Send request.
+        return $this->post(
+            endpoint: 'subscribers',
+            args: $options
+        );
+    }
+
+    /**
+     * Create multiple subscribers.
+     *
+     * @param array<int,array<string,string>> $subscribers  Subscribers.
+     * @param string                          $callback_url URL to notify for large batch size when async processing complete.
+     *
+     * @since 2.0.0
+     *
+     * @see https://developers.convertkit.com/v4.html#bulk-create-subscribers
+     *
+     * @return mixed
+     */
+    public function create_subscribers(array $subscribers, string $callback_url = '')
+    {
+        // Build parameters.
+        $options = ['subscribers' => $subscribers];
+
+        if (!empty($callback_url)) {
+            $options['callback_url'] = $callback_url;
+        }
+
+        // Send request.
+        return $this->post(
+            endpoint: 'bulk/subscribers',
+            args: $options
+        );
+    }
+
     /**
      * Get the ConvertKit subscriber ID associated with email address if it exists.
      * Return false if subscriber not found.
@@ -941,27 +1090,18 @@ public function get_resources(string $resource)
      *
      * @throws \InvalidArgumentException If the email address is not a valid email format.
      *
-     * @see https://developers.convertkit.com/#list-subscribers
+     * @see https://developers.convertkit.com/v4.html#get-a-subscriber
      *
      * @return false|integer
      */
     public function get_subscriber_id(string $email_address)
     {
-        if (!filter_var($email_address, FILTER_VALIDATE_EMAIL)) {
-            throw new \InvalidArgumentException('Email address is not a valid email format.');
-        }
-
         $subscribers = $this->get(
             'subscribers',
             ['email_address' => $email_address]
         );
 
-        if (!$subscribers) {
-            $this->create_log('No subscribers');
-            return false;
-        }
-
-        if ($subscribers->total_subscribers === 0) {
+        if (!count($subscribers->subscribers)) {
             $this->create_log('No subscribers');
             return false;
         }
@@ -975,7 +1115,7 @@ public function get_subscriber_id(string $email_address)
      *
      * @param integer $subscriber_id Subscriber ID.
      *
-     * @see https://developers.convertkit.com/#view-a-single-subscriber
+     * @see https://developers.convertkit.com/v4.html#get-a-subscriber
      *
      * @return false|integer
      */
@@ -992,7 +1132,7 @@ public function get_subscriber(int $subscriber_id)
      * @param string                $email_address New Email Address.
      * @param array<string, string> $fields        Updated Custom Fields.
      *
-     * @see https://developers.convertkit.com/#update-subscriber
+     * @see https://developers.convertkit.com/v4.html#update-a-subscriber
      *
      * @return false|mixed
      */
@@ -1023,56 +1163,64 @@ public function update_subscriber(
     }
 
     /**
-     * Unsubscribe an email address from all forms and sequences.
+     * Unsubscribe an email address.
      *
      * @param string $email Email Address.
      *
-     * @see https://developers.convertkit.com/#unsubscribe-subscriber
+     * @see https://developers.convertkit.com/v4.html#unsubscribe-subscriber
      *
      * @return false|object
      */
     public function unsubscribe(string $email)
     {
-        return $this->put(
-            'unsubscribe',
-            ['email' => $email]
+        return $this->post(
+            sprintf(
+                'subscribers/%s/unsubscribe',
+                $this->get_subscriber_id($email)
+            )
         );
     }
 
     /**
-     * Remove subscription from a form
+     * Unsubscribe the given subscriber ID.
      *
-     * @param array<string, string> $options Array of user data (email).
+     * @param integer $subscriber_id Subscriber ID.
      *
-     * @see https://developers.convertkit.com/#unsubscribe-subscriber
+     * @see https://developers.convertkit.com/v4.html#unsubscribe-subscriber
      *
      * @return false|object
      */
-    public function form_unsubscribe(array $options)
+    public function unsubscribe_by_id(int $subscriber_id)
     {
-        // This function is deprecated in 1.0, as we prefer functions with structured arguments.
-        // This function name is also misleading, as it doesn't just unsubscribe the email
-        // address from forms.
-        trigger_error(
-            'form_unsubscribe() is deprecated in 1.0.  Use unsubscribe($email) instead.',
-            E_USER_NOTICE
-        );
-
-        return $this->put('unsubscribe', $options);
+        return $this->post(sprintf('subscribers/%s/unsubscribe', $subscriber_id));
     }
 
     /**
      * Get a list of the tags for a subscriber.
      *
      * @param integer $subscriber_id Subscriber ID.
+     * @param string  $after_cursor  Return results after the given pagination cursor.
+     * @param string  $before_cursor Return results before the given pagination cursor.
+     * @param integer $per_page      Number of results to return.
      *
-     * @see https://developers.convertkit.com/#list-tags-for-a-subscriber
+     * @see https://developers.convertkit.com/v4.html#list-tags-for-a-subscriber
      *
      * @return false|array<int,\stdClass>
      */
-    public function get_subscriber_tags(int $subscriber_id)
-    {
-        return $this->get(sprintf('subscribers/%s/tags', $subscriber_id));
+    public function get_subscriber_tags(
+        int $subscriber_id,
+        string $after_cursor = '',
+        string $before_cursor = '',
+        int $per_page = 100
+    ) {
+        return $this->get(
+            endpoint: sprintf('subscribers/%s/tags', $subscriber_id),
+            args: $this->build_pagination_params(
+                after_cursor: $after_cursor,
+                before_cursor: $before_cursor,
+                per_page: $per_page
+            )
+        );
     }
 
     /**
diff --git a/tests/ConvertKitAPITest.php b/tests/ConvertKitAPITest.php
index ca2e5c1..8b2b2ff 100644
--- a/tests/ConvertKitAPITest.php
+++ b/tests/ConvertKitAPITest.php
@@ -2078,6 +2078,580 @@ public function testAddSubscriberToFormByIDWithInvalidSubscriberID()
         );
     }
 
+    /**
+     * Test that get_subscribers() returns the expected data.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribers()
+    {
+        $result = $this->api->get_subscribers();
+
+        // Assert subscribers and pagination exist.
+        $this->assertDataExists($result, 'subscribers');
+        $this->assertPaginationExists($result);
+    }
+
+    /**
+     * Test that get_subscribers() returns the expected data when
+     * searching by an email address.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersByEmailAddress()
+    {
+        $result = $this->api->get_subscribers(
+            email_address: $_ENV['CONVERTKIT_API_SUBSCRIBER_EMAIL']
+        );
+
+        // Assert subscribers and pagination exist.
+        $this->assertDataExists($result, 'subscribers');
+        $this->assertPaginationExists($result);
+
+        // Assert correct subscriber returned.
+        $this->assertEquals(
+            $result->subscribers[0]->email_address,
+            $_ENV['CONVERTKIT_API_SUBSCRIBER_EMAIL']
+        );
+    }
+
+    /**
+     * Test that get_subscribers() returns the expected data
+     * when the subscription status is bounced.
+     *
+     * @since   1.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersWithBouncedSubscriberState()
+    {
+        $result = $this->api->get_subscribers(
+            subscriber_state: 'bounced'
+        );
+
+        // Assert subscribers and pagination exist.
+        $this->assertDataExists($result, 'subscribers');
+        $this->assertPaginationExists($result);
+
+        // Check the correct subscribers were returned.
+        $this->assertEquals($result->subscribers[0]->state, 'bounced');
+    }
+
+    /**
+     * Test that get_subscribers() returns the expected data
+     * when the created_after parameter is used.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersWithCreatedAfterParam()
+    {
+        $date = new \DateTime('2024-01-01');
+        $result = $this->api->get_subscribers(
+            created_after: $date
+        );
+
+        // Assert subscribers and pagination exist.
+        $this->assertDataExists($result, 'subscribers');
+        $this->assertPaginationExists($result);
+
+        // Check the correct subscribers were returned.
+        $this->assertGreaterThanOrEqual(
+            $date->format('Y-m-d'),
+            date('Y-m-d', strtotime($result->subscribers[0]->created_at))
+        );
+    }
+
+    /**
+     * Test that get_subscribers() returns the expected data
+     * when the created_before parameter is used.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersWithCreatedBeforeParam()
+    {
+        $date = new \DateTime('2024-01-01');
+        $result = $this->api->get_subscribers(
+            created_before: $date
+        );
+
+        // Assert subscribers and pagination exist.
+        $this->assertDataExists($result, 'subscribers');
+        $this->assertPaginationExists($result);
+
+        // Check the correct subscribers were returned.
+        $this->assertLessThanOrEqual(
+            $date->format('Y-m-d'),
+            date('Y-m-d', strtotime($result->subscribers[0]->created_at))
+        );
+    }
+
+    /**
+     * Test that get_subscribers() returns the expected data
+     * when the updated_after parameter is used.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersWithUpdatedAfterParam()
+    {
+        $date = new \DateTime('2024-01-01');
+        $result = $this->api->get_subscribers(
+            updated_after: $date
+        );
+
+        // Assert subscribers and pagination exist.
+        $this->assertDataExists($result, 'subscribers');
+        $this->assertPaginationExists($result);
+    }
+
+    /**
+     * Test that get_subscribers() returns the expected data
+     * when the updated_before parameter is used.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersWithUpdatedBeforeParam()
+    {
+        $date = new \DateTime('2024-01-01');
+        $result = $this->api->get_subscribers(
+            updated_before: $date
+        );
+
+        // Assert subscribers and pagination exist.
+        $this->assertDataExists($result, 'subscribers');
+        $this->assertPaginationExists($result);
+    }
+
+    /**
+     * Test that get_subscribers() returns the expected data
+     * when the sort_field parameter is used.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersWithSortFieldParam()
+    {
+        $result = $this->api->get_subscribers(
+            sort_field: 'id'
+        );
+
+        // Assert subscribers and pagination exist.
+        $this->assertDataExists($result, 'subscribers');
+        $this->assertPaginationExists($result);
+
+        // Assert sorting is honored by ID in descending (default) order.
+        $this->assertLessThanOrEqual(
+            $result->subscribers[0]->id,
+            $result->subscribers[1]->id
+        );
+    }
+
+    /**
+     * Test that get_subscribers() returns the expected data
+     * when the sort_order parameter is used.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersWithSortOrderParam()
+    {
+        $result = $this->api->get_subscribers(
+            sort_order: 'asc'
+        );
+
+        // Assert subscribers and pagination exist.
+        $this->assertDataExists($result, 'subscribers');
+        $this->assertPaginationExists($result);
+
+        // Assert sorting is honored by ID (default) in ascending order.
+        $this->assertGreaterThanOrEqual(
+            $result->subscribers[0]->id,
+            $result->subscribers[1]->id
+        );
+    }
+
+    /**
+     * Test that get_subscribers() returns the expected data
+     * when pagination parameters and per_page limits are specified.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersPagination()
+    {
+        $result = $this->api->get_subscribers(
+            per_page: 1
+        );
+
+        // Assert subscribers and pagination exist.
+        $this->assertDataExists($result, 'subscribers');
+        $this->assertPaginationExists($result);
+
+        // Assert a single subscriber was returned.
+        $this->assertCount(1, $result->subscribers);
+
+        // Assert has_previous_page and has_next_page are correct.
+        $this->assertFalse($result->pagination->has_previous_page);
+        $this->assertTrue($result->pagination->has_next_page);
+
+        // Use pagination to fetch next page.
+        $result = $this->api->get_subscribers(
+            per_page: 1,
+            after_cursor: $result->pagination->end_cursor
+        );
+
+        // Assert subscribers and pagination exist.
+        $this->assertDataExists($result, 'subscribers');
+        $this->assertPaginationExists($result);
+
+        // Assert a single subscriber was returned.
+        $this->assertCount(1, $result->subscribers);
+
+        // Assert has_previous_page and has_next_page are correct.
+        $this->assertTrue($result->pagination->has_previous_page);
+        $this->assertTrue($result->pagination->has_next_page);
+
+        // Use pagination to fetch previous page.
+        $result = $this->api->get_subscribers(
+            per_page: 1,
+            before_cursor: $result->pagination->start_cursor
+        );
+
+        // Assert subscribers and pagination exist.
+        $this->assertDataExists($result, 'subscribers');
+        $this->assertPaginationExists($result);
+
+        // Assert a single subscriber was returned.
+        $this->assertCount(1, $result->subscribers);
+
+        // Assert has_previous_page and has_next_page are correct.
+        $this->assertFalse($result->pagination->has_previous_page);
+        $this->assertTrue($result->pagination->has_next_page);
+    }
+
+    /**
+     * Test that get_subscribers() throws a ClientException when an invalid
+     * email address is specified.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersWithInvalidEmailAddress()
+    {
+        $this->expectException(ClientException::class);
+        $result = $this->api->get_subscribers(
+            email_address: 'not-an-email-address'
+        );
+    }
+
+    /**
+     * Test that get_subscribers() throws a ClientException when an invalid
+     * subscriber state is specified.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersWithInvalidSubscriberState()
+    {
+        $this->expectException(ClientException::class);
+        $result = $this->api->get_subscribers(
+            subscriber_state: 'not-an-valid-state'
+        );
+    }
+
+    /**
+     * Test that get_subscribers() throws a ClientException when an invalid
+     * sort field is specified.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersWithInvalidSortFieldParam()
+    {
+        $this->expectException(ClientException::class);
+        $result = $this->api->get_subscribers(
+            sort_field: 'not-a-valid-sort-field'
+        );
+    }
+
+    /**
+     * Test that get_subscribers() throws a ClientException when an invalid
+     * sort order is specified.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersWithInvalidSortOrderParam()
+    {
+        $this->expectException(ClientException::class);
+        $result = $this->api->get_subscribers(
+            sort_order: 'not-a-valid-sort-order'
+        );
+    }
+
+    /**
+     * Test that get_subscribers() throws a ClientException when an invalid
+     * pagination parameters are specified.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscribersWithInvalidPagination()
+    {
+        $this->expectException(ClientException::class);
+        $result = $this->api->get_subscribers(
+            after_cursor: 'not-a-valid-cursor'
+        );
+    }
+
+    /**
+     * Test that create_subscriber() returns the expected data.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testCreateSubscriber()
+    {
+        $emailAddress = $this->generateEmailAddress();
+        $result = $this->api->create_subscriber(
+            email_address: $emailAddress
+        );
+
+        // Assert subscriber exists with correct data.
+        $this->assertEquals($result->subscriber->email_address, $emailAddress);
+
+        // Unsubscribe to cleanup test.
+        $this->api->unsubscribe_by_id($result->subscriber->id);
+    }
+
+    /**
+     * Test that create_subscriber() returns the expected data
+     * when a first name is included.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testCreateSubscriberWithFirstName()
+    {
+        $firstName = 'FirstName';
+        $emailAddress = $this->generateEmailAddress();
+        $result = $this->api->create_subscriber(
+            email_address: $emailAddress,
+            first_name: $firstName
+        );
+
+        // Assert subscriber exists with correct data.
+        $this->assertEquals($result->subscriber->email_address, $emailAddress);
+        $this->assertEquals($result->subscriber->first_name, $firstName);
+
+        // Unsubscribe to cleanup test.
+        $this->api->unsubscribe_by_id($result->subscriber->id);
+    }
+
+    /**
+     * Test that create_subscriber() returns the expected data
+     * when a subscriber state is included.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testCreateSubscriberWithSubscriberState()
+    {
+        $subscriberState = 'cancelled';
+        $emailAddress = $this->generateEmailAddress();
+        $result = $this->api->create_subscriber(
+            email_address: $emailAddress,
+            subscriber_state: $subscriberState
+        );
+
+        // Assert subscriber exists with correct data.
+        $this->assertEquals($result->subscriber->email_address, $emailAddress);
+        $this->assertEquals($result->subscriber->state, $subscriberState);
+
+        // Unsubscribe to cleanup test.
+        $this->api->unsubscribe_by_id($result->subscriber->id);
+    }
+
+    /**
+     * Test that create_subscriber() returns the expected data
+     * when custom field data is included.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testCreateSubscriberWithCustomFields()
+    {
+        $lastName = 'LastName';
+        $emailAddress = $this->generateEmailAddress();
+        $result = $this->api->create_subscriber(
+            email_address: $emailAddress,
+            fields: [
+                'last_name' => $lastName
+            ]
+        );
+
+        // Assert subscriber exists with correct data.
+        $this->assertEquals($result->subscriber->email_address, $emailAddress);
+        $this->assertEquals($result->subscriber->fields->last_name, $lastName);
+
+        // Unsubscribe to cleanup test.
+        $this->api->unsubscribe_by_id($result->subscriber->id);
+    }
+
+    /**
+     * Test that create_subscriber() throws a ClientException when an invalid
+     * email address is specified.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testCreateSubscriberWithInvalidEmailAddress()
+    {
+        $this->expectException(ClientException::class);
+        $result = $this->api->create_subscriber(
+            email_address: 'not-an-email-address'
+        );
+    }
+
+    /**
+     * Test that create_subscriber() throws a ClientException when an invalid
+     * subscriber state is specified.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testCreateSubscriberWithInvalidSubscriberState()
+    {
+        $this->expectException(ClientException::class);
+        $emailAddress = $this->generateEmailAddress();
+        $result = $this->api->create_subscriber(
+            email_address: $emailAddress,
+            subscriber_state: 'not-a-valid-state'
+        );
+    }
+
+    /**
+     * Test that create_subscriber() returns the expected data
+     * when an invalid custom field is included.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testCreateSubscriberWithInvalidCustomFields()
+    {
+
+        $emailAddress = $this->generateEmailAddress();
+        $result = $this->api->create_subscriber(
+            email_address: $emailAddress,
+            fields: [
+                'not_a_custom_field' => 'value'
+            ]
+        );
+
+        // Assert subscriber exists with correct data.
+        $this->assertEquals($result->subscriber->email_address, $emailAddress);
+
+        // Unsubscribe to cleanup test.
+        $this->api->unsubscribe_by_id($result->subscriber->id);
+    }
+
+    /**
+     * Test that create_subscribers() returns the expected data.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testCreateSubscribers()
+    {
+        $subscribers = [
+            [
+                'email_address' => str_replace('@convertkit.com', '-1@convertkit.com', $this->generateEmailAddress()),
+            ],
+            [
+                'email_address' => str_replace('@convertkit.com', '-2@convertkit.com', $this->generateEmailAddress()),
+            ],
+        ];
+        $result = $this->api->create_subscribers($subscribers);
+
+        // Assert no failures.
+        $this->assertCount(0, $result->failures);
+
+        // Assert subscribers exists with correct data.
+        foreach ($result->subscribers as $i => $subscriber) {
+            $this->assertEquals($subscriber->email_address, $subscribers[$i]['email_address']);
+
+            // Unsubscribe to cleanup test.
+            $this->api->unsubscribe_by_id($subscriber->id);
+        }
+    }
+
+    /**
+     * Test that create_subscribers() throws a ClientException when no data is specified.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testCreateSubscribersWithBlankData()
+    {
+        $this->expectException(ClientException::class);
+        $result = $this->api->create_subscribers([
+            [],
+        ]);
+    }
+
+    /**
+     * Test that create_subscribers() returns the expected data when invalid email addresses
+     * are specified.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testCreateSubscribersWithInvalidEmailAddresses()
+    {
+        $subscribers = [
+            [
+                'email_address' => 'not-an-email-address',
+            ],
+            [
+                'email_address' => 'not-an-email-address-again',
+            ],
+        ];
+        $result = $this->api->create_subscribers($subscribers);
+
+        // Assert no subscribers were added.
+        $this->assertCount(0, $result->subscribers);
+        $this->assertCount(2, $result->failures);
+    }
+
     /**
      * Test that get_subscriber_id() returns the expected data.
      *
@@ -2087,8 +2661,6 @@ public function testAddSubscriberToFormByIDWithInvalidSubscriberID()
      */
     public function testGetSubscriberID()
     {
-        $this->markTestIncomplete();
-
         $subscriber_id = $this->api->get_subscriber_id($_ENV['CONVERTKIT_API_SUBSCRIBER_EMAIL']);
         $this->assertIsInt($subscriber_id);
         $this->assertEquals($subscriber_id, (int) $_ENV['CONVERTKIT_API_SUBSCRIBER_ID']);
@@ -2104,9 +2676,7 @@ public function testGetSubscriberID()
      */
     public function testGetSubscriberIDWithInvalidEmailAddress()
     {
-        $this->markTestIncomplete();
-
-        $this->expectException(InvalidArgumentException::class);
+        $this->expectException(ClientException::class);
         $result = $this->api->get_subscriber_id('not-an-email-address');
     }
 
@@ -2120,8 +2690,6 @@ public function testGetSubscriberIDWithInvalidEmailAddress()
      */
     public function testGetSubscriberIDWithNotSubscribedEmailAddress()
     {
-        $this->markTestIncomplete();
-
         $result = $this->api->get_subscriber_id('not-a-subscriber@test.com');
         $this->assertFalse($result);
     }
@@ -2135,16 +2703,11 @@ public function testGetSubscriberIDWithNotSubscribedEmailAddress()
      */
     public function testGetSubscriber()
     {
-        $this->markTestIncomplete();
+        $result = $this->api->get_subscriber((int) $_ENV['CONVERTKIT_API_SUBSCRIBER_ID']);
 
-        $subscriber = $this->api->get_subscriber((int) $_ENV['CONVERTKIT_API_SUBSCRIBER_ID']);
-        $this->assertInstanceOf('stdClass', $subscriber);
-        $this->assertArrayHasKey('subscriber', get_object_vars($subscriber));
-        $this->assertArrayHasKey('id', get_object_vars($subscriber->subscriber));
-        $this->assertEquals(
-            get_object_vars($subscriber->subscriber)['id'],
-            (int) $_ENV['CONVERTKIT_API_SUBSCRIBER_ID']
-        );
+        // Assert subscriber exists with correct data.
+        $this->assertEquals($result->subscriber->id, $_ENV['CONVERTKIT_API_SUBSCRIBER_ID']);
+        $this->assertEquals($result->subscriber->email_address, $_ENV['CONVERTKIT_API_SUBSCRIBER_EMAIL']);
     }
 
     /**
@@ -2157,8 +2720,6 @@ public function testGetSubscriber()
      */
     public function testGetSubscriberWithInvalidSubscriberID()
     {
-        $this->markTestIncomplete();
-
         $this->expectException(ClientException::class);
         $subscriber = $this->api->get_subscriber(12345);
     }
@@ -2172,13 +2733,11 @@ public function testGetSubscriberWithInvalidSubscriberID()
      */
     public function testUpdateSubscriberWithNoChanges()
     {
-        $this->markTestIncomplete();
-
         $result = $this->api->update_subscriber($_ENV['CONVERTKIT_API_SUBSCRIBER_ID']);
-        $this->assertInstanceOf('stdClass', $result);
-        $this->assertArrayHasKey('subscriber', get_object_vars($result));
-        $this->assertArrayHasKey('id', get_object_vars($result->subscriber));
-        $this->assertEquals(get_object_vars($result->subscriber)['id'], $_ENV['CONVERTKIT_API_SUBSCRIBER_ID']);
+
+        // Assert subscriber exists with correct data.
+        $this->assertEquals($result->subscriber->id, $_ENV['CONVERTKIT_API_SUBSCRIBER_ID']);
+        $this->assertEquals($result->subscriber->email_address, $_ENV['CONVERTKIT_API_SUBSCRIBER_EMAIL']);
     }
 
     /**
@@ -2190,33 +2749,31 @@ public function testUpdateSubscriberWithNoChanges()
      */
     public function testUpdateSubscriberFirstName()
     {
-        $this->markTestIncomplete();
-
         // Add a subscriber.
-        $email = $this->generateEmailAddress();
-        $result = $this->api->add_subscriber_to_sequence(
-            sequence_id: $_ENV['CONVERTKIT_API_SEQUENCE_ID'],
-            email: $email
+        $firstName = 'FirstName';
+        $emailAddress = $this->generateEmailAddress();
+        $result = $this->api->create_subscriber(
+            email_address: $emailAddress
         );
 
+        // Assert subscriber created with no first name.
+        $this->assertNull($result->subscriber->first_name);
+
         // Get subscriber ID.
-        $subscriberID = $result->subscription->subscriber->id;
+        $subscriberID = $result->subscriber->id;
 
         // Update subscriber's first name.
         $result = $this->api->update_subscriber(
             subscriber_id: $subscriberID,
-            first_name: 'First Name'
+            first_name: $firstName
         );
 
-        // Confirm the change is reflected in the subscriber.
-        $this->assertInstanceOf('stdClass', $result);
-        $this->assertArrayHasKey('subscriber', get_object_vars($result));
-        $this->assertArrayHasKey('id', get_object_vars($result->subscriber));
-        $this->assertEquals(get_object_vars($result->subscriber)['id'], $subscriberID);
-        $this->assertEquals(get_object_vars($result->subscriber)['first_name'], 'First Name');
+        // Assert changes were made.
+        $this->assertEquals($result->subscriber->id, $subscriberID);
+        $this->assertEquals($result->subscriber->first_name, $firstName);
 
-        // Unsubscribe.
-        $this->api->unsubscribe($email);
+        // Unsubscribe to cleanup test.
+        $this->api->unsubscribe_by_id($result->subscriber->id);
     }
 
     /**
@@ -2228,17 +2785,17 @@ public function testUpdateSubscriberFirstName()
      */
     public function testUpdateSubscriberEmailAddress()
     {
-        $this->markTestIncomplete();
-
         // Add a subscriber.
-        $email = $this->generateEmailAddress();
-        $result = $this->api->add_subscriber_to_sequence(
-            sequence_id: $_ENV['CONVERTKIT_API_SEQUENCE_ID'],
-            email: $email
+        $emailAddress = $this->generateEmailAddress();
+        $result = $this->api->create_subscriber(
+            email_address: $emailAddress
         );
 
+        // Assert subscriber created.
+        $this->assertEquals($result->subscriber->email_address, $emailAddress);
+
         // Get subscriber ID.
-        $subscriberID = $result->subscription->subscriber->id;
+        $subscriberID = $result->subscriber->id;
 
         // Update subscriber's email address.
         $newEmail = $this->generateEmailAddress();
@@ -2247,15 +2804,12 @@ public function testUpdateSubscriberEmailAddress()
             email_address: $newEmail
         );
 
-        // Confirm the change is reflected in the subscriber.
-        $this->assertInstanceOf('stdClass', $result);
-        $this->assertArrayHasKey('subscriber', get_object_vars($result));
-        $this->assertArrayHasKey('id', get_object_vars($result->subscriber));
-        $this->assertEquals(get_object_vars($result->subscriber)['id'], $subscriberID);
-        $this->assertEquals(get_object_vars($result->subscriber)['email_address'], $newEmail);
+        // Assert changes were made.
+        $this->assertEquals($result->subscriber->id, $subscriberID);
+        $this->assertEquals($result->subscriber->email_address, $newEmail);
 
-        // Unsubscribe.
-        $this->api->unsubscribe($newEmail);
+        // Unsubscribe to cleanup test.
+        $this->api->unsubscribe_by_id($result->subscriber->id);
     }
 
     /**
@@ -2267,35 +2821,33 @@ public function testUpdateSubscriberEmailAddress()
      */
     public function testUpdateSubscriberCustomFields()
     {
-        $this->markTestIncomplete();
-
         // Add a subscriber.
-        $email = $this->generateEmailAddress();
-        $result = $this->api->add_subscriber_to_sequence(
-            sequence_id: $_ENV['CONVERTKIT_API_SEQUENCE_ID'],
-            email: $email
+        $lastName = 'LastName';
+        $emailAddress = $this->generateEmailAddress();
+        $result = $this->api->create_subscriber(
+            email_address: $emailAddress
         );
 
+        // Assert subscriber created.
+        $this->assertEquals($result->subscriber->email_address, $emailAddress);
+
         // Get subscriber ID.
-        $subscriberID = $result->subscription->subscriber->id;
+        $subscriberID = $result->subscriber->id;
 
-        // Update subscriber's email address.
+        // Update subscriber's custom fields.
         $result = $this->api->update_subscriber(
             subscriber_id: $subscriberID,
             fields: [
-                'last_name' => 'Last Name',
+                'last_name' => $lastName,
             ]
         );
 
-        // Confirm the change is reflected in the subscriber.
-        $this->assertInstanceOf('stdClass', $result);
-        $this->assertArrayHasKey('subscriber', get_object_vars($result));
-        $this->assertArrayHasKey('id', get_object_vars($result->subscriber));
-        $this->assertEquals(get_object_vars($result->subscriber)['id'], $subscriberID);
-        $this->assertEquals($result->subscriber->fields->last_name, 'Last Name');
+        // Assert changes were made.
+        $this->assertEquals($result->subscriber->id, $subscriberID);
+        $this->assertEquals($result->subscriber->fields->last_name, $lastName);
 
-        // Unsubscribe.
-        $this->api->unsubscribe($email);
+        // Unsubscribe to cleanup test.
+        $this->api->unsubscribe_by_id($result->subscriber->id);
     }
 
     /**
@@ -2308,8 +2860,6 @@ public function testUpdateSubscriberCustomFields()
      */
     public function testUpdateSubscriberWithInvalidSubscriberID()
     {
-        $this->markTestIncomplete();
-
         $this->expectException(ClientException::class);
         $subscriber = $this->api->update_subscriber(12345);
     }
@@ -2323,23 +2873,14 @@ public function testUpdateSubscriberWithInvalidSubscriberID()
      */
     public function testUnsubscribe()
     {
-        $this->markTestIncomplete();
-
         // Add a subscriber.
-        $email = $this->generateEmailAddress();
-        $result = $this->api->add_subscriber_to_sequence(
-            sequence_id: $_ENV['CONVERTKIT_API_SEQUENCE_ID'],
-            email: $email
+        $emailAddress = $this->generateEmailAddress();
+        $result = $this->api->create_subscriber(
+            email_address: $emailAddress
         );
 
         // Unsubscribe.
-        $result = $this->api->unsubscribe($email);
-
-        // Confirm the change is reflected in the subscriber.
-        $this->assertInstanceOf('stdClass', $result);
-        $this->assertArrayHasKey('subscriber', get_object_vars($result));
-        $this->assertEquals($result->subscriber->email_address, $email);
-        $this->assertEquals($result->subscriber->state, 'cancelled');
+        $this->assertNull($this->api->unsubscribe($emailAddress));
     }
 
     /**
@@ -2352,8 +2893,6 @@ public function testUnsubscribe()
      */
     public function testUnsubscribeWithNotSubscribedEmailAddress()
     {
-        $this->markTestIncomplete();
-
         $this->expectException(ClientException::class);
         $subscriber = $this->api->unsubscribe('not-subscribed@convertkit.com');
     }
@@ -2368,12 +2907,43 @@ public function testUnsubscribeWithNotSubscribedEmailAddress()
      */
     public function testUnsubscribeWithInvalidEmailAddress()
     {
-        $this->markTestIncomplete();
-
         $this->expectException(ClientException::class);
         $subscriber = $this->api->unsubscribe('invalid-email');
     }
 
+    /**
+     * Test that unsubscribe() works with a valid subscriber ID.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testUnsubscribeByID()
+    {
+        // Add a subscriber.
+        $emailAddress = $this->generateEmailAddress();
+        $result = $this->api->create_subscriber(
+            email_address: $emailAddress
+        );
+
+        // Unsubscribe.
+        $this->assertNull($this->api->unsubscribe_by_id($result->subscriber->id));
+    }
+
+    /**
+     * Test that unsubscribe() throws a ClientException when an invalid
+     * subscriber ID is specified.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testUnsubscribeByIDWithInvalidSubscriberID()
+    {
+        $this->expectException(ClientException::class);
+        $subscriber = $this->api->unsubscribe_by_id(12345);
+    }
+
     /**
      * Test that get_subscriber_tags() returns the expected data.
      *
@@ -2383,11 +2953,11 @@ public function testUnsubscribeWithInvalidEmailAddress()
      */
     public function testGetSubscriberTags()
     {
-        $this->markTestIncomplete();
+        $result = $this->api->get_subscriber_tags((int) $_ENV['CONVERTKIT_API_SUBSCRIBER_ID']);
 
-        $subscriber = $this->api->get_subscriber_tags((int) $_ENV['CONVERTKIT_API_SUBSCRIBER_ID']);
-        $this->assertInstanceOf('stdClass', $subscriber);
-        $this->assertArrayHasKey('tags', get_object_vars($subscriber));
+        // Assert tags and pagination exist.
+        $this->assertDataExists($result, 'tags');
+        $this->assertPaginationExists($result);
     }
 
     /**
@@ -2400,12 +2970,74 @@ public function testGetSubscriberTags()
      */
     public function testGetSubscriberTagsWithInvalidSubscriberID()
     {
-        $this->markTestIncomplete();
-
         $this->expectException(ClientException::class);
         $subscriber = $this->api->get_subscriber_tags(12345);
     }
 
+    /**
+     * Test that get_subscriber_tags() returns the expected data
+     * when a valid Subscriber ID is specified and pagination parameters
+     * and per_page limits are specified.
+     *
+     * @since   2.0.0
+     *
+     * @return void
+     */
+    public function testGetSubscriberTagsPagination()
+    {
+        $result = $this->api->get_subscriber_tags(
+            subscriber_id: (int) $_ENV['CONVERTKIT_API_SUBSCRIBER_ID'],
+            per_page: 1
+        );
+
+        // Assert tags and pagination exist.
+        $this->assertDataExists($result, 'tags');
+        $this->assertPaginationExists($result);
+
+        // Assert a single tag was returned.
+        $this->assertCount(1, $result->tags);
+
+        // Assert has_previous_page and has_next_page are correct.
+        $this->assertFalse($result->pagination->has_previous_page);
+        $this->assertTrue($result->pagination->has_next_page);
+
+        // Use pagination to fetch next page.
+        $result = $this->api->get_subscriber_tags(
+            subscriber_id: (int) $_ENV['CONVERTKIT_API_SUBSCRIBER_ID'],
+            per_page: 1,
+            after_cursor: $result->pagination->end_cursor
+        );
+
+        // Assert tags and pagination exist.
+        $this->assertDataExists($result, 'tags');
+        $this->assertPaginationExists($result);
+
+        // Assert a single tag was returned.
+        $this->assertCount(1, $result->tags);
+
+        // Assert has_previous_page and has_next_page are correct.
+        $this->assertTrue($result->pagination->has_previous_page);
+        $this->assertTrue($result->pagination->has_next_page);
+
+        // Use pagination to fetch previous page.
+        $result = $this->api->get_subscriber_tags(
+            subscriber_id: (int) $_ENV['CONVERTKIT_API_SUBSCRIBER_ID'],
+            per_page: 1,
+            before_cursor: $result->pagination->start_cursor
+        );
+
+        // Assert tags and pagination exist.
+        $this->assertDataExists($result, 'tags');
+        $this->assertPaginationExists($result);
+
+        // Assert a single tag was returned.
+        $this->assertCount(1, $result->tags);
+
+        // Assert has_previous_page and has_next_page are correct.
+        $this->assertFalse($result->pagination->has_previous_page);
+        $this->assertTrue($result->pagination->has_next_page);
+    }
+
     /**
      * Test that create_broadcast(), update_broadcast() and destroy_broadcast() works
      * when specifying valid published_at and send_at values.